niceSOFT/sqlite: Official Git mirror of the SQLite source tree

src/expr.c
7 722 строки262 KB
drh
Fix problems with expressions like "(?,?,?) IN (SELECT c,b,a FROM ...)" when there is an index on columns "c", "b" and "a", but not in that order.
04 июн 2026, 14:24
04 июн 2026, 14:241ba44fc
/*
** 2001 September 15
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains routines used for analyzing expressions and
** for generating VDBE code that evaluates expressions in SQLite.
*/
#include "sqliteInt.h"

/* Forward declarations */
static void exprCodeBetween(Parse*,Expr*,int,void(*)(Parse*,Expr*,int,int),int);
static int exprCodeVector(Parse *pParse, Expr *p, int *piToFree);

/*
** Return the affinity character for a single column of a table.
*/
char sqlite3TableColumnAffinity(const Table *pTab, int iCol){
  if( iCol<0 || NEVER(iCol>=pTab->nCol) ) return SQLITE_AFF_INTEGER;
  return pTab->aCol[iCol].affinity;
}

/*
** Return the 'affinity' of the expression pExpr if any.
**
** If pExpr is a column, a reference to a column via an 'AS' alias,
** or a sub-select with a column as the return value, then the
** affinity of that column is returned. Otherwise, 0x00 is returned,
** indicating no affinity for the expression.
**
** i.e. the WHERE clause expressions in the following statements all
** have an affinity:
**
** CREATE TABLE t1(a);
** SELECT * FROM t1 WHERE a;
** SELECT a AS b FROM t1 WHERE b;
** SELECT * FROM t1 WHERE (select a from t1);
*/
char sqlite3ExprAffinity(const Expr *pExpr){
  int op;
  op = pExpr->op;
  while( 1 /* exit-by-break */ ){
    if( op==TK_COLUMN || (op==TK_AGG_COLUMN && pExpr->y.pTab!=0) ){
      assert( ExprUseYTab(pExpr) );
      assert( pExpr->y.pTab!=0 );
      return sqlite3TableColumnAffinity(pExpr->y.pTab, pExpr->iColumn);
    }
    if( op==TK_SELECT ){
      assert( ExprUseXSelect(pExpr) );
      assert( pExpr->x.pSelect!=0 );
      assert( pExpr->x.pSelect->pEList!=0 );
      assert( pExpr->x.pSelect->pEList->a[0].pExpr!=0 );
      return sqlite3ExprAffinity(pExpr->x.pSelect->pEList->a[0].pExpr);
    }
#ifndef SQLITE_OMIT_CAST
    if( op==TK_CAST ){
      assert( !ExprHasProperty(pExpr, EP_IntValue) );
      return sqlite3AffinityType(pExpr->u.zToken, 0);
    }
#endif
    if( op==TK_SELECT_COLUMN ){
      assert( pExpr->pLeft!=0 && ExprUseXSelect(pExpr->pLeft) );
      assert( pExpr->iColumn < pExpr->iTable );
      assert( pExpr->iColumn >= 0 );
      assert( pExpr->iTable==pExpr->pLeft->x.pSelect->pEList->nExpr );
      return sqlite3ExprAffinity(
          pExpr->pLeft->x.pSelect->pEList->a[pExpr->iColumn].pExpr
      );
    }
    if( op==TK_VECTOR
     || (op==TK_FUNCTION && pExpr->affExpr==SQLITE_AFF_DEFER)
    ){
      assert( ExprUseXList(pExpr) );
      return sqlite3ExprAffinity(pExpr->x.pList->a[0].pExpr);
    }
    if( ExprHasProperty(pExpr, EP_Skip|EP_IfNullRow) ){
      assert( pExpr->op==TK_COLLATE
           || pExpr->op==TK_IF_NULL_ROW
           || (pExpr->op==TK_REGISTER && pExpr->op2==TK_IF_NULL_ROW) );
      pExpr = pExpr->pLeft;
      op = pExpr->op;
      continue;
    }
    if( op!=TK_REGISTER ) break;
    op = pExpr->op2;
    if( NEVER( op==TK_REGISTER ) ) break;
  }
  return pExpr->affExpr;
}

/*
** Make a guess at all the possible datatypes of the result that could
** be returned by an expression.  Return a bitmask indicating the answer:
**
**     0x01         Numeric
**     0x02         Text
**     0x04         Blob
**
** If the expression must return NULL, then 0x00 is returned.
*/
int sqlite3ExprDataType(const Expr *pExpr){
  while( pExpr ){
    switch( pExpr->op ){
      case TK_COLLATE:
      case TK_IF_NULL_ROW:
      case TK_UPLUS:  {
        pExpr = pExpr->pLeft;
        break;
      }
      case TK_NULL: {
        pExpr = 0;
        break;
      }
      case TK_STRING: {
        return 0x02;
      }
      case TK_BLOB: {
        return 0x04;
      }
      case TK_CONCAT: {
        return 0x06;
      }
      case TK_VARIABLE:
      case TK_AGG_FUNCTION:
      case TK_FUNCTION: {
        return 0x07;
      }
      case TK_COLUMN:
      case TK_AGG_COLUMN:
      case TK_SELECT:
      case TK_CAST:
      case TK_SELECT_COLUMN:
      case TK_VECTOR:  {
        int aff = sqlite3ExprAffinity(pExpr);
        if( aff>=SQLITE_AFF_NUMERIC ) return 0x05;
        if( aff==SQLITE_AFF_TEXT )    return 0x06;
        return 0x07;
      }
      case TK_CASE: {
        int res = 0;
        int ii;
        ExprList *pList = pExpr->x.pList;
        assert( ExprUseXList(pExpr) && pList!=0 );
        assert( pList->nExpr > 0);
        for(ii=1; ii<pList->nExpr; ii+=2){
          res |= sqlite3ExprDataType(pList->a[ii].pExpr);
        }
        if( pList->nExpr % 2 ){
          res |= sqlite3ExprDataType(pList->a[pList->nExpr-1].pExpr);
        }
        return res;
      }
      default: {
        return 0x01;
      }
    } /* End of switch(op) */
  } /* End of while(pExpr) */
  return 0x00;
}

/*
** Set the collating sequence for expression pExpr to be the collating
** sequence named by pToken.   Return a pointer to a new Expr node that
** implements the COLLATE operator.
**
** If a memory allocation error occurs, that fact is recorded in pParse->db
** and the pExpr parameter is returned unchanged.
*/
Expr *sqlite3ExprAddCollateToken(
  const Parse *pParse,     /* Parsing context */
  Expr *pExpr,             /* Add the "COLLATE" clause to this expression */
  const Token *pCollName,  /* Name of collating sequence */
  int dequote              /* True to dequote pCollName */
){
  if( pCollName->n>0 ){
    Expr *pNew = sqlite3ExprAlloc(pParse->db, TK_COLLATE, pCollName, dequote);
    if( pNew ){
      pNew->pLeft = pExpr;
      pNew->flags |= EP_Collate|EP_Skip;
      pExpr = pNew;
    }
  }
  return pExpr;
}
Expr *sqlite3ExprAddCollateString(
  const Parse *pParse,  /* Parsing context */
  Expr *pExpr,          /* Add the "COLLATE" clause to this expression */
  const char *zC        /* The collating sequence name */
){
  Token s;
  assert( zC!=0 );
  sqlite3TokenInit(&s, (char*)zC);
  return sqlite3ExprAddCollateToken(pParse, pExpr, &s, 0);
}

/*
** Skip over any TK_COLLATE operators.
*/
Expr *sqlite3ExprSkipCollate(Expr *pExpr){
  while( pExpr && ExprHasProperty(pExpr, EP_Skip) ){
    assert( pExpr->op==TK_COLLATE );
    pExpr = pExpr->pLeft;
  }  
  return pExpr;
}

/*
** Skip over any TK_COLLATE operators and/or any unlikely()
** or likelihood() or likely() functions at the root of an
** expression.
*/
Expr *sqlite3ExprSkipCollateAndLikely(Expr *pExpr){
  while( pExpr && ExprHasProperty(pExpr, EP_Skip|EP_Unlikely) ){
    if( ExprHasProperty(pExpr, EP_Unlikely) ){
      assert( ExprUseXList(pExpr) );
      assert( pExpr->x.pList->nExpr>0 );
      assert( pExpr->op==TK_FUNCTION );
      pExpr = pExpr->x.pList->a[0].pExpr;
    }else if( pExpr->op==TK_COLLATE ){
      pExpr = pExpr->pLeft;
    }else{
      break;
    }
  }  
  return pExpr;
}

/*
** Return the collation sequence for the expression pExpr. If
** there is no defined collating sequence, return NULL.
**
** See also: sqlite3ExprNNCollSeq()
**
** The sqlite3ExprNNCollSeq() works the same exact that it returns the
** default collation if pExpr has no defined collation.
**
** The collating sequence might be determined by a COLLATE operator
** or by the presence of a column with a defined collating sequence.
** COLLATE operators take first precedence.  Left operands take
** precedence over right operands.
*/
CollSeq *sqlite3ExprCollSeq(Parse *pParse, const Expr *pExpr){
  sqlite3 *db = pParse->db;
  CollSeq *pColl = 0;
  const Expr *p = pExpr;
  while( p ){
    int op = p->op;
    if( op==TK_REGISTER ) op = p->op2;
    if( (op==TK_AGG_COLUMN && p->y.pTab!=0)
     || op==TK_COLUMN || op==TK_TRIGGER
    ){
      int j;
      assert( ExprUseYTab(p) );
      assert( p->y.pTab!=0 );
      if( (j = p->iColumn)>=0 ){
        const char *zColl = sqlite3ColumnColl(&p->y.pTab->aCol[j]);
        pColl = sqlite3FindCollSeq(db, ENC(db), zColl, 0);
      }
      break;
    }
    if( op==TK_CAST || op==TK_UPLUS ){
      p = p->pLeft;
      continue;
    }
    if( op==TK_VECTOR
     || (op==TK_FUNCTION && p->affExpr==SQLITE_AFF_DEFER)
    ){
      assert( ExprUseXList(p) );
      p = p->x.pList->a[0].pExpr;
      continue;
    }
    if( op==TK_COLLATE ){
      assert( !ExprHasProperty(p, EP_IntValue) );
      pColl = sqlite3GetCollSeq(pParse, ENC(db), 0, p->u.zToken);
      break;
    }
    if( p->flags & EP_Collate ){
      if( p->pLeft && (p->pLeft->flags & EP_Collate)!=0 ){
        p = p->pLeft;
      }else{
        Expr *pNext  = p->pRight;
        /* The Expr.x union is never used at the same time as Expr.pRight */
        assert( !ExprUseXList(p) || p->x.pList==0 || p->pRight==0 );
        if( ExprUseXList(p) && p->x.pList!=0 && !db->mallocFailed ){
          int i;
          for(i=0; i<p->x.pList->nExpr; i++){
            if( ExprHasProperty(p->x.pList->a[i].pExpr, EP_Collate) ){
              pNext = p->x.pList->a[i].pExpr;
              break;
            }
          }
        }
        p = pNext;
      }
    }else{
      break;
    }
  }
  if( sqlite3CheckCollSeq(pParse, pColl) ){
    pColl = 0;
  }
  return pColl;
}

/*
** Return the collation sequence for the expression pExpr. If
** there is no defined collating sequence, return a pointer to the
** default collation sequence.
**
** See also: sqlite3ExprCollSeq()
**
** The sqlite3ExprCollSeq() routine works the same except that it
** returns NULL if there is no defined collation.
*/
CollSeq *sqlite3ExprNNCollSeq(Parse *pParse, const Expr *pExpr){
  CollSeq *p = sqlite3ExprCollSeq(pParse, pExpr);
  if( p==0 ) p = pParse->db->pDfltColl;
  assert( p!=0 );
  return p;
}

/*
** Return TRUE if the two expressions have equivalent collating sequences.
*/
int sqlite3ExprCollSeqMatch(Parse *pParse, const Expr *pE1, const Expr *pE2){
  CollSeq *pColl1 = sqlite3ExprNNCollSeq(pParse, pE1);
  CollSeq *pColl2 = sqlite3ExprNNCollSeq(pParse, pE2);
  return sqlite3StrICmp(pColl1->zName, pColl2->zName)==0;
}

/*
** pExpr is an operand of a comparison operator.  aff2 is the
** type affinity of the other operand.  This routine returns the
** type affinity that should be used for the comparison operator.
*/
char sqlite3CompareAffinity(const Expr *pExpr, char aff2){
  char aff1 = sqlite3ExprAffinity(pExpr);
  if( aff1>SQLITE_AFF_NONE && aff2>SQLITE_AFF_NONE ){
    /* Both sides of the comparison are columns. If one has numeric
    ** affinity, use that. Otherwise use no affinity.
    */
    if( sqlite3IsNumericAffinity(aff1) || sqlite3IsNumericAffinity(aff2) ){
      return SQLITE_AFF_NUMERIC;
    }else{
      return SQLITE_AFF_BLOB;
    }
  }else{
    /* One side is a column, the other is not. Use the columns affinity. */
    assert( aff1<=SQLITE_AFF_NONE || aff2<=SQLITE_AFF_NONE );
    return (aff1<=SQLITE_AFF_NONE ? aff2 : aff1) | SQLITE_AFF_NONE;
  }
}

/*
** pExpr is a comparison operator.  Return the type affinity that should
** be applied to both operands prior to doing the comparison.
*/
static char comparisonAffinity(const Expr *pExpr){
  char aff;
  assert( pExpr->op==TK_EQ || pExpr->op==TK_IN || pExpr->op==TK_LT ||
          pExpr->op==TK_GT || pExpr->op==TK_GE || pExpr->op==TK_LE ||
          pExpr->op==TK_NE || pExpr->op==TK_IS || pExpr->op==TK_ISNOT );
  assert( pExpr->pLeft );
  aff = sqlite3ExprAffinity(pExpr->pLeft);
  if( pExpr->pRight ){
    aff = sqlite3CompareAffinity(pExpr->pRight, aff);
  }else if( ExprUseXSelect(pExpr) ){
    aff = sqlite3CompareAffinity(pExpr->x.pSelect->pEList->a[0].pExpr, aff);
  }else if( aff==0 ){
    aff = SQLITE_AFF_BLOB;
  }
  return aff;
}

/*
** pExpr is a comparison expression, eg. '=', '<', IN(...) etc.
** idx_affinity is the affinity of an indexed column. Return true
** if the index with affinity idx_affinity may be used to implement
** the comparison in pExpr.
*/
int sqlite3IndexAffinityOk(const Expr *pExpr, char idx_affinity){
  char aff = comparisonAffinity(pExpr);
  if( aff<SQLITE_AFF_TEXT ){
    return 1;
  }
  if( aff==SQLITE_AFF_TEXT ){
    return idx_affinity==SQLITE_AFF_TEXT;
  }
  return sqlite3IsNumericAffinity(idx_affinity);
}

/*
** Return the P5 value that should be used for a binary comparison
** opcode (OP_Eq, OP_Ge etc.) used to compare pExpr1 and pExpr2.
*/
static u8 binaryCompareP5(
  const Expr *pExpr1,   /* Left operand */
  const Expr *pExpr2,   /* Right operand */
  int jumpIfNull        /* Extra flags added to P5 */
){
  u8 aff = (char)sqlite3ExprAffinity(pExpr2);
  aff = (u8)sqlite3CompareAffinity(pExpr1, aff) | (u8)jumpIfNull;
  return aff;
}

/*
** Return a pointer to the collation sequence that should be used by
** a binary comparison operator comparing pLeft and pRight.
**
** If the left hand expression has a collating sequence type, then it is
** used. Otherwise the collation sequence for the right hand expression
** is used, or the default (BINARY) if neither expression has a collating
** type.
**
** Argument pRight (but not pLeft) may be a null pointer. In this case,
** it is not considered.
*/
CollSeq *sqlite3BinaryCompareCollSeq(
  Parse *pParse,
  const Expr *pLeft,
  const Expr *pRight
){
  CollSeq *pColl;
  assert( pLeft );
  if( pLeft->flags & EP_Collate ){
    pColl = sqlite3ExprCollSeq(pParse, pLeft);
  }else if( pRight && (pRight->flags & EP_Collate)!=0 ){
    pColl = sqlite3ExprCollSeq(pParse, pRight);
  }else{
    pColl = sqlite3ExprCollSeq(pParse, pLeft);
    if( !pColl ){
      pColl = sqlite3ExprCollSeq(pParse, pRight);
    }
  }
  return pColl;
}

/* Expression p is a comparison operator.  Return a collation sequence
** appropriate for the comparison operator.
**
** This is normally just a wrapper around sqlite3BinaryCompareCollSeq().
** However, if the OP_Commuted flag is set, then the order of the operands
** is reversed in the sqlite3BinaryCompareCollSeq() call so that the
** correct collating sequence is found.
*/
CollSeq *sqlite3ExprCompareCollSeq(Parse *pParse, const Expr *p){
  if( ExprHasProperty(p, EP_Commuted) ){
    return sqlite3BinaryCompareCollSeq(pParse, p->pRight, p->pLeft);
  }else{
    return sqlite3BinaryCompareCollSeq(pParse, p->pLeft, p->pRight);
  }
}

/*
** Generate code for a comparison operator.
*/
static int codeCompare(
  Parse *pParse,    /* The parsing (and code generating) context */
  Expr *pLeft,      /* The left operand */
  Expr *pRight,     /* The right operand */
  int opcode,       /* The comparison opcode */
  int in1, int in2, /* Register holding operands */
  int dest,         /* Jump here if true.  */
  int jumpIfNull,   /* If true, jump if either operand is NULL */
  int isCommuted    /* The comparison has been commuted */
){
  int p5;
  int addr;
  CollSeq *p4;

  if( pParse->nErr ) return 0;
  if( isCommuted ){
    p4 = sqlite3BinaryCompareCollSeq(pParse, pRight, pLeft);
  }else{
    p4 = sqlite3BinaryCompareCollSeq(pParse, pLeft, pRight);
  }
  p5 = binaryCompareP5(pLeft, pRight, jumpIfNull);
  addr = sqlite3VdbeAddOp4(pParse->pVdbe, opcode, in2, dest, in1,
                           (void*)p4, P4_COLLSEQ);
  sqlite3VdbeChangeP5(pParse->pVdbe, (u16)p5);
  return addr;
}

/*
** Return true if expression pExpr is a vector, or false otherwise.
**
** A vector is defined as any expression that results in two or more
** columns of result.  Every TK_VECTOR node is an vector because the
** parser will not generate a TK_VECTOR with fewer than two entries.
** But a TK_SELECT might be either a vector or a scalar. It is only
** considered a vector if it has two or more result columns.
*/
int sqlite3ExprIsVector(const Expr *pExpr){
  return sqlite3ExprVectorSize(pExpr)>1;
}

/*
** If the expression passed as the only argument is of type TK_VECTOR
** return the number of expressions in the vector. Or, if the expression
** is a sub-select, return the number of columns in the sub-select. For
** any other type of expression, return 1.
*/
int sqlite3ExprVectorSize(const Expr *pExpr){
  u8 op = pExpr->op;
  if( op==TK_REGISTER ) op = pExpr->op2;
  if( op==TK_VECTOR ){
    assert( ExprUseXList(pExpr) );
    return pExpr->x.pList->nExpr;
  }else if( op==TK_SELECT ){
    assert( ExprUseXSelect(pExpr) );
    return pExpr->x.pSelect->pEList->nExpr;
  }else{
    return 1;
  }
}

/*
** Return a pointer to a subexpression of pVector that is the i-th
** column of the vector (numbered starting with 0).  The caller must
** ensure that i is within range.
**
** If pVector is really a scalar (and "scalar" here includes subqueries
** that return a single column!) then return pVector unmodified.
**
** pVector retains ownership of the returned subexpression.
**
** If the vector is a (SELECT ...) then the expression returned is
** just the expression for the i-th term of the result set, and may
** not be ready for evaluation because the table cursor has not yet
** been positioned.
*/
Expr *sqlite3VectorFieldSubexpr(Expr *pVector, int i){
  assert( i<sqlite3ExprVectorSize(pVector) || pVector->op==TK_ERROR );
  if( sqlite3ExprIsVector(pVector) ){
    assert( pVector->op2==0 || pVector->op==TK_REGISTER );
    if( pVector->op==TK_SELECT || pVector->op2==TK_SELECT ){
      assert( ExprUseXSelect(pVector) );
      return pVector->x.pSelect->pEList->a[i].pExpr;
    }else{
      assert( ExprUseXList(pVector) );
      return pVector->x.pList->a[i].pExpr;
    }
  }
  return pVector;
}

/*
** Compute and return a new Expr object which when passed to
** sqlite3ExprCode() will generate all necessary code to compute
** the iField-th column of the vector expression pVector.
**
** It is ok for pVector to be a scalar (as long as iField==0). 
** In that case, this routine works like sqlite3ExprDup().
**
** The caller owns the returned Expr object and is responsible for
** ensuring that the returned value eventually gets freed.
**
** The caller retains ownership of pVector.  If pVector is a TK_SELECT,
** then the returned object will reference pVector and so pVector must remain
** valid for the life of the returned object.  If pVector is a TK_VECTOR
** or a scalar expression, then it can be deleted as soon as this routine
** returns.
**
** A trick to cause a TK_SELECT pVector to be deleted together with
** the returned Expr object is to attach the pVector to the pRight field
** of the returned TK_SELECT_COLUMN Expr object.
*/
Expr *sqlite3ExprForVectorField(
  Parse *pParse,       /* Parsing context */
  Expr *pVector,       /* The vector.  List of expressions or a sub-SELECT */
  int iField,          /* Which column of the vector to return */
  int nField           /* Total number of columns in the vector */
){
  Expr *pRet;
  if( pVector->op==TK_SELECT ){
    assert( ExprUseXSelect(pVector) );
    /* The TK_SELECT_COLUMN Expr node:
    **
    ** pLeft:           pVector containing TK_SELECT.  Not deleted.
    ** pRight:          not used.  But recursively deleted.
    ** iColumn:         Index of a column in pVector
    ** iTable:          0 or the number of columns on the LHS of an assignment
    ** pLeft->iTable:   First in an array of register holding result, or 0
    **                  if the result is not yet computed.
    **
    ** sqlite3ExprDelete() specifically skips the recursive delete of
    ** pLeft on TK_SELECT_COLUMN nodes.  But pRight is followed, so pVector
    ** can be attached to pRight to cause this node to take ownership of
    ** pVector.  Typically there will be multiple TK_SELECT_COLUMN nodes
    ** with the same pLeft pointer to the pVector, but only one of them
    ** will own the pVector.
    */
    pRet = sqlite3PExpr(pParse, TK_SELECT_COLUMN, 0, 0);
    if( pRet ){
      ExprSetProperty(pRet, EP_FullSize);
      pRet->iTable = nField;
      pRet->iColumn = iField;
      pRet->pLeft = pVector;
    }
  }else{
    if( pVector->op==TK_VECTOR ){
      Expr **ppVector;
      assert( ExprUseXList(pVector) );
      ppVector = &pVector->x.pList->a[iField].pExpr;
      pVector = *ppVector;
      if( IN_RENAME_OBJECT ){
        /* This must be a vector UPDATE inside a trigger */
        *ppVector = 0;
        return pVector;
      }
    }
    pRet = sqlite3ExprDup(pParse->db, pVector, 0);
  }
  return pRet;
}

/*
** If expression pExpr is of type TK_SELECT, generate code to evaluate
** it. Return the register in which the result is stored (or, if the
** sub-select returns more than one column, the first in an array
** of registers in which the result is stored).
**
** If pExpr is not a TK_SELECT expression, return 0.
*/
static int exprCodeSubselect(Parse *pParse, Expr *pExpr){
  int reg = 0;
#ifndef SQLITE_OMIT_SUBQUERY
  if( pExpr->op==TK_SELECT ){
    reg = sqlite3CodeSubselect(pParse, pExpr);
  }
#endif
  return reg;
}

/*
** Argument pVector points to a vector expression - either a TK_VECTOR
** or TK_SELECT that returns more than one column. This function returns
** the register number of a register that contains the value of
** element iField of the vector.
**
** If pVector is a TK_SELECT expression, then code for it must have
** already been generated using the exprCodeSubselect() routine. In this
** case parameter regSelect should be the first in an array of registers
** containing the results of the sub-select.
**
** If pVector is of type TK_VECTOR, then code for the requested field
** is generated. In this case (*pRegFree) may be set to the number of
** a temporary register to be freed by the caller before returning.
**
** Before returning, output parameter (*ppExpr) is set to point to the
** Expr object corresponding to element iElem of the vector.
*/
static int exprVectorRegister(
  Parse *pParse,                  /* Parse context */
  Expr *pVector,                  /* Vector to extract element from */
  int iField,                     /* Field to extract from pVector */
  int regSelect,                  /* First in array of registers */
  Expr **ppExpr,                  /* OUT: Expression element */
  int *pRegFree                   /* OUT: Temp register to free */
){
  u8 op = pVector->op;
  assert( op==TK_VECTOR || op==TK_REGISTER || op==TK_SELECT || op==TK_ERROR );
  if( op==TK_REGISTER ){
    *ppExpr = sqlite3VectorFieldSubexpr(pVector, iField);
    return pVector->iTable+iField;
  }
  if( op==TK_SELECT ){
    assert( ExprUseXSelect(pVector) );
    *ppExpr = pVector->x.pSelect->pEList->a[iField].pExpr;
     return regSelect+iField;
  }
  if( op==TK_VECTOR ){
    assert( ExprUseXList(pVector) );
    *ppExpr = pVector->x.pList->a[iField].pExpr;
    return sqlite3ExprCodeTemp(pParse, *ppExpr, pRegFree);
  }
  return 0;
}

/*
** Expression pExpr is a comparison between two vector values. Compute
** the result of the comparison (1, 0, or NULL) and write that
** result into register dest.
**
** The caller must satisfy the following preconditions:
**
**    if pExpr->op==TK_IS:      op==TK_EQ and p5==SQLITE_NULLEQ
**    if pExpr->op==TK_ISNOT:   op==TK_NE and p5==SQLITE_NULLEQ
**    otherwise:                op==pExpr->op and p5==0
*/
static void codeVectorCompare(
  Parse *pParse,        /* Code generator context */
  Expr *pExpr,          /* The comparison operation */
  int dest,             /* Write results into this register */
  u8 op,                /* Comparison operator */
  u8 p5                 /* SQLITE_NULLEQ or zero */
){
  Vdbe *v = pParse->pVdbe;
  Expr *pLeft = pExpr->pLeft;
  Expr *pRight = pExpr->pRight;
  int nLeft = sqlite3ExprVectorSize(pLeft);
  int i;
  int regLeft = 0;
  int regRight = 0;
  u8 opx = op;
  int addrCmp = 0;
  int addrDone = sqlite3VdbeMakeLabel(pParse);
  int isCommuted = ExprHasProperty(pExpr,EP_Commuted);

  assert( !ExprHasVVAProperty(pExpr,EP_Immutable) );
  if( pParse->nErr ) return;
  if( nLeft!=sqlite3ExprVectorSize(pRight) ){
    sqlite3ErrorMsg(pParse, "row value misused");
    return;
  }
  assert( pExpr->op==TK_EQ || pExpr->op==TK_NE
       || pExpr->op==TK_IS || pExpr->op==TK_ISNOT
       || pExpr->op==TK_LT || pExpr->op==TK_GT
       || pExpr->op==TK_LE || pExpr->op==TK_GE
  );
  assert( pExpr->op==op || (pExpr->op==TK_IS && op==TK_EQ)
            || (pExpr->op==TK_ISNOT && op==TK_NE) );
  assert( p5==0 || pExpr->op!=op );
  assert( p5==SQLITE_NULLEQ || pExpr->op==op );

  if( op==TK_LE ) opx = TK_LT;
  if( op==TK_GE ) opx = TK_GT;
  if( op==TK_NE ) opx = TK_EQ;

  regLeft = exprCodeSubselect(pParse, pLeft);
  regRight = exprCodeSubselect(pParse, pRight);

  sqlite3VdbeAddOp2(v, OP_Integer, 1, dest);
  for(i=0; 1 /*Loop exits by "break"*/; i++){
    int regFree1 = 0, regFree2 = 0;
    Expr *pL = 0, *pR = 0;
    int r1, r2;
    assert( i>=0 && i<nLeft );
    if( addrCmp ) sqlite3VdbeJumpHere(v, addrCmp);
    r1 = exprVectorRegister(pParse, pLeft, i, regLeft, &pL, &regFree1);
    r2 = exprVectorRegister(pParse, pRight, i, regRight, &pR, &regFree2);
    addrCmp = sqlite3VdbeCurrentAddr(v);
    codeCompare(pParse, pL, pR, opx, r1, r2, addrDone, p5, isCommuted);
    testcase(op==OP_Lt); VdbeCoverageIf(v,op==OP_Lt);
    testcase(op==OP_Le); VdbeCoverageIf(v,op==OP_Le);
    testcase(op==OP_Gt); VdbeCoverageIf(v,op==OP_Gt);
    testcase(op==OP_Ge); VdbeCoverageIf(v,op==OP_Ge);
    testcase(op==OP_Eq); VdbeCoverageIf(v,op==OP_Eq);
    testcase(op==OP_Ne); VdbeCoverageIf(v,op==OP_Ne);
    sqlite3ReleaseTempReg(pParse, regFree1);
    sqlite3ReleaseTempReg(pParse, regFree2);
    if( (opx==TK_LT || opx==TK_GT) && i<nLeft-1 ){
      addrCmp = sqlite3VdbeAddOp0(v, OP_ElseEq);
      testcase(opx==TK_LT); VdbeCoverageIf(v,opx==TK_LT);
      testcase(opx==TK_GT); VdbeCoverageIf(v,opx==TK_GT);
    }
    if( p5==SQLITE_NULLEQ ){
      sqlite3VdbeAddOp2(v, OP_Integer, 0, dest);
    }else{
      sqlite3VdbeAddOp3(v, OP_ZeroOrNull, r1, dest, r2);
    }
    if( i==nLeft-1 ){
      break;
    }
    if( opx==TK_EQ ){
      sqlite3VdbeAddOp2(v, OP_NotNull, dest, addrDone); VdbeCoverage(v);
    }else{
      assert( op==TK_LT || op==TK_GT || op==TK_LE || op==TK_GE );
      sqlite3VdbeAddOp2(v, OP_Goto, 0, addrDone);
      if( i==nLeft-2 ) opx = op;
    }
  }
  sqlite3VdbeJumpHere(v, addrCmp);
  sqlite3VdbeResolveLabel(v, addrDone);
  if( op==TK_NE ){
    sqlite3VdbeAddOp2(v, OP_Not, dest, dest);
  }
}

#if SQLITE_MAX_EXPR_DEPTH>0
/*
** Check that argument nHeight is less than or equal to the maximum
** expression depth allowed. If it is not, leave an error message in
** pParse.
*/
int sqlite3ExprCheckHeight(Parse *pParse, int nHeight){
  int rc = SQLITE_OK;
  int mxHeight = pParse->db->aLimit[SQLITE_LIMIT_EXPR_DEPTH];
  if( nHeight>mxHeight ){
    sqlite3ErrorMsg(pParse,
       "Expression tree is too large (maximum depth %d)", mxHeight
    );
    rc = SQLITE_ERROR;
  }
  return rc;
}

/* The following three functions, heightOfExpr(), heightOfExprList()
** and heightOfSelect(), are used to determine the maximum height
** of any expression tree referenced by the structure passed as the
** first argument.
**
** If this maximum height is greater than the current value pointed
** to by pnHeight, the second parameter, then set *pnHeight to that
** value.
*/
static void heightOfExpr(const Expr *p, int *pnHeight){
  if( p ){
    if( p->nHeight>*pnHeight ){
      *pnHeight = p->nHeight;
    }
  }
}
static void heightOfExprList(const ExprList *p, int *pnHeight){
  if( p ){
    int i;
    for(i=0; i<p->nExpr; i++){
      heightOfExpr(p->a[i].pExpr, pnHeight);
    }
  }
}
static void heightOfSelect(const Select *pSelect, int *pnHeight){
  const Select *p;
  for(p=pSelect; p; p=p->pPrior){
    heightOfExpr(p->pWhere, pnHeight);
    heightOfExpr(p->pHaving, pnHeight);
    heightOfExpr(p->pLimit, pnHeight);
    heightOfExprList(p->pEList, pnHeight);
    heightOfExprList(p->pGroupBy, pnHeight);
    heightOfExprList(p->pOrderBy, pnHeight);
  }
}

/*
** Set the Expr.nHeight variable in the structure passed as an
** argument. An expression with no children, Expr.pList or
** Expr.pSelect member has a height of 1. Any other expression
** has a height equal to the maximum height of any other
** referenced Expr plus one.
**
** Also propagate EP_Propagate flags up from Expr.x.pList to Expr.flags,
** if appropriate.
*/
static void exprSetHeight(Expr *p){
  int nHeight = p->pLeft ? p->pLeft->nHeight : 0;
  if( NEVER(p->pRight) && p->pRight->nHeight>nHeight ){
    nHeight = p->pRight->nHeight;
  }
  if( ExprUseXSelect(p) ){
    heightOfSelect(p->x.pSelect, &nHeight);
  }else if( p->x.pList ){
    heightOfExprList(p->x.pList, &nHeight);
    p->flags |= EP_Propagate & sqlite3ExprListFlags(p->x.pList);
  }
  p->nHeight = nHeight + 1;
}

/*
** Set the Expr.nHeight variable using the exprSetHeight() function. If
** the height is greater than the maximum allowed expression depth,
** leave an error in pParse.
**
** Also propagate all EP_Propagate flags from the Expr.x.pList into
** Expr.flags.
*/
void sqlite3ExprSetHeightAndFlags(Parse *pParse, Expr *p){
  if( pParse->nErr ) return;
  exprSetHeight(p);
  sqlite3ExprCheckHeight(pParse, p->nHeight);
}

/*
** Return the maximum height of any expression tree referenced
** by the select statement passed as an argument.
*/
int sqlite3SelectExprHeight(const Select *p){
  int nHeight = 0;
  heightOfSelect(p, &nHeight);
  return nHeight;
}
#else /* ABOVE:  Height enforcement enabled.  BELOW: Height enforcement off */
/*
** Propagate all EP_Propagate flags from the Expr.x.pList into
** Expr.flags.
*/
void sqlite3ExprSetHeightAndFlags(Parse *pParse, Expr *p){
  if( pParse->nErr ) return;
  if( p && ExprUseXList(p) && p->x.pList ){
    p->flags |= EP_Propagate & sqlite3ExprListFlags(p->x.pList);
  }
}
#define exprSetHeight(y)
#endif /* SQLITE_MAX_EXPR_DEPTH>0 */

/*
** Set the error offset for an Expr node, if possible.
*/
void sqlite3ExprSetErrorOffset(Expr *pExpr, int iOfst){
  if( pExpr==0 ) return;
  if( NEVER(ExprUseWJoin(pExpr)) ) return;
  pExpr->w.iOfst = iOfst;
}

/*
** This routine is the core allocator for Expr nodes.
**
** Construct a new expression node and return a pointer to it.  Memory
** for this node and for the pToken argument is a single allocation
** obtained from sqlite3DbMalloc().  The calling function
** is responsible for making sure the node eventually gets freed.
**
** If dequote is true, then the token (if it exists) is dequoted.
** If dequote is false, no dequoting is performed.  The deQuote
** parameter is ignored if pToken is NULL or if the token does not
** appear to be quoted.  If the quotes were of the form "..." (double-quotes)
** then the EP_DblQuoted flag is set on the expression node.
**
** Special case (tag-20240227-a):  If op==TK_INTEGER and pToken points to
** a string that can be translated into a 32-bit integer, then the token is
** not stored in u.zToken.  Instead, the integer values is written
** into u.iValue and the EP_IntValue flag is set. No extra storage
** is allocated to hold the integer text and the dequote flag is ignored.
** See also tag-20240227-b.
*/
Expr *sqlite3ExprAlloc(
  sqlite3 *db,            /* Handle for sqlite3DbMallocRawNN() */
  int op,                 /* Expression opcode */
  const Token *pToken,    /* Token argument.  Might be NULL */
  int dequote             /* True to dequote */
){
  Expr *pNew;
  int nExtra = pToken ? pToken->n+1 : 0;

  assert( db!=0 );
  pNew = sqlite3DbMallocRawNN(db, sizeof(Expr)+nExtra);
  if( pNew ){
    memset(pNew, 0, sizeof(Expr));
    pNew->op = (u8)op;
    pNew->iAgg = -1;
    if( nExtra ){
      assert( pToken!=0 );
      pNew->u.zToken = (char*)&pNew[1];
      assert( pToken->z!=0 || pToken->n==0 );
      if( pToken->n ) memcpy(pNew->u.zToken, pToken->z, pToken->n);
      pNew->u.zToken[pToken->n] = 0;
      if( dequote && sqlite3Isquote(pNew->u.zToken[0]) ){
        sqlite3DequoteExpr(pNew);
      }
    }
#if SQLITE_MAX_EXPR_DEPTH>0
    pNew->nHeight = 1;
#endif 
  }
  return pNew;
}

/*
** Allocate a new expression node from a zero-terminated token that has
** already been dequoted.
*/
Expr *sqlite3Expr(
  sqlite3 *db,            /* Handle for sqlite3DbMallocZero() (may be null) */
  int op,                 /* Expression opcode */
  const char *zToken      /* Token argument.  Might be NULL */
){
  Token x;
  x.z = zToken;
  x.n = sqlite3Strlen30(zToken);
  return sqlite3ExprAlloc(db, op, &x, 0);
}

/*
** Allocate an expression for a 32-bit signed integer literal.
*/
Expr *sqlite3ExprInt32(sqlite3 *db, int iVal){
  Expr *pNew = sqlite3DbMallocRawNN(db, sizeof(Expr));
  if( pNew ){
    memset(pNew, 0, sizeof(Expr));
    pNew->op = TK_INTEGER;
    pNew->iAgg = -1;
    pNew->flags = EP_IntValue|EP_Leaf|(iVal?EP_IsTrue:EP_IsFalse);
    pNew->u.iValue = iVal;
#if SQLITE_MAX_EXPR_DEPTH>0
    pNew->nHeight = 1;
#endif 
  }
  return pNew;
}

/*
** Attach subtrees pLeft and pRight to the Expr node pRoot.
**
** If pRoot==NULL that means that a memory allocation error has occurred.
** In that case, delete the subtrees pLeft and pRight.
*/
void sqlite3ExprAttachSubtrees(
  sqlite3 *db,
  Expr *pRoot,
  Expr *pLeft,
  Expr *pRight
){
  if( pRoot==0 ){
    assert( db->mallocFailed );
    sqlite3ExprDelete(db, pLeft);
    sqlite3ExprDelete(db, pRight);
  }else{
    assert( ExprUseXList(pRoot) );
    assert( pRoot->x.pSelect==0 );
    if( pRight ){
      pRoot->pRight = pRight;
      pRoot->flags |= EP_Propagate & pRight->flags;
#if SQLITE_MAX_EXPR_DEPTH>0
      pRoot->nHeight = pRight->nHeight+1;
    }else{
      pRoot->nHeight = 1;
#endif
    }
    if( pLeft ){
      pRoot->pLeft = pLeft;
      pRoot->flags |= EP_Propagate & pLeft->flags;
#if SQLITE_MAX_EXPR_DEPTH>0
      if( pLeft->nHeight>=pRoot->nHeight ){
        pRoot->nHeight = pLeft->nHeight+1;
      }
#endif
    }
  }
}

/*
** Allocate an Expr node which joins as many as two subtrees.
**
** One or both of the subtrees can be NULL.  Return a pointer to the new
** Expr node.  Or, if an OOM error occurs, set pParse->db->mallocFailed,
** free the subtrees and return NULL.
*/
Expr *sqlite3PExpr(
  Parse *pParse,          /* Parsing context */
  int op,                 /* Expression opcode */
  Expr *pLeft,            /* Left operand */
  Expr *pRight            /* Right operand */
){
  Expr *p;
  p = sqlite3DbMallocRawNN(pParse->db, sizeof(Expr));
  if( p ){
    memset(p, 0, sizeof(Expr));
    p->op = op & 0xff;
    p->iAgg = -1;
    sqlite3ExprAttachSubtrees(pParse->db, p, pLeft, pRight);
    sqlite3ExprCheckHeight(pParse, p->nHeight);
  }else{
    sqlite3ExprDelete(pParse->db, pLeft);
    sqlite3ExprDelete(pParse->db, pRight);
  }
  return p;
}

/*
** Add pSelect to the Expr.x.pSelect field.  Or, if pExpr is NULL (due
** do a memory allocation failure) then delete the pSelect object.
*/
void sqlite3PExprAddSelect(Parse *pParse, Expr *pExpr, Select *pSelect){
  if( pExpr ){
    pExpr->x.pSelect = pSelect;
    ExprSetProperty(pExpr, EP_xIsSelect|EP_Subquery);
    sqlite3ExprSetHeightAndFlags(pParse, pExpr);
  }else{
    assert( pParse->db->mallocFailed );
    sqlite3SelectDelete(pParse->db, pSelect);
  }
}

/*
** Expression list pEList is a list of vector values. This function
** converts the contents of pEList to a VALUES(...) Select statement
** returning 1 row for each element of the list. For example, the
** expression list:
**
**   ( (1,2), (3,4) (5,6) )
**
** is translated to the equivalent of:
**
**   VALUES(1,2), (3,4), (5,6)
**
** Each of the vector values in pEList must contain exactly nElem terms.
** If a list element that is not a vector or does not contain nElem terms,
** an error message is left in pParse.
**
** This is used as part of processing IN(...) expressions with a list
** of vectors on the RHS. e.g. "... IN ((1,2), (3,4), (5,6))".
*/
Select *sqlite3ExprListToValues(Parse *pParse, int nElem, ExprList *pEList){
  int ii;
  Select *pRet = 0;
  assert( nElem>1 );
  for(ii=0; ii<pEList->nExpr; ii++){
    Select *pSel;
    Expr *pExpr = pEList->a[ii].pExpr;
    int nExprElem;
    if( pExpr->op==TK_VECTOR ){
      assert( ExprUseXList(pExpr) );
      nExprElem = pExpr->x.pList->nExpr;
    }else{
      nExprElem = 1;
    }
    if( nExprElem!=nElem ){
      sqlite3ErrorMsg(pParse, "IN(...) element has %d term%s - expected %d",
          nExprElem, nExprElem>1?"s":"", nElem
      );
      break;
    }
    assert( ExprUseXList(pExpr) );
    pSel = sqlite3SelectNew(pParse, pExpr->x.pList, 0, 0, 0, 0, 0, SF_Values,0);
    pExpr->x.pList = 0;
    if( pSel ){
      if( pRet ){
        pSel->op = TK_ALL;
        pSel->pPrior = pRet;
      }
      pRet = pSel;
    }
  }

  if( pRet && pRet->pPrior ){
    pRet->selFlags |= SF_MultiValue;
  }
  sqlite3ExprListDelete(pParse->db, pEList);
  return pRet;
}

/*
** Join two expressions using an AND operator.  If either expression is
** NULL, then just return the other expression.
**
** If one side or the other of the AND is known to be false, and neither side
** is part of an ON clause, then instead of returning an AND expression,
** just return a constant expression with a value of false.
*/
Expr *sqlite3ExprAnd(Parse *pParse, Expr *pLeft, Expr *pRight){
  sqlite3 *db = pParse->db;
  if( pLeft==0  ){
    return pRight;
  }else if( pRight==0 ){
    return pLeft;
  }else{
    u32 f = pLeft->flags | pRight->flags;
    if( (f&(EP_OuterON|EP_InnerON|EP_IsFalse|EP_HasFunc))==EP_IsFalse
     && !IN_RENAME_OBJECT
    ){
      sqlite3ExprDeferredDelete(pParse, pLeft);
      sqlite3ExprDeferredDelete(pParse, pRight);
      return sqlite3ExprInt32(db, 0);
    }else{
      return sqlite3PExpr(pParse, TK_AND, pLeft, pRight);
    }
  }
}

/*
** Construct a new expression node for a function with multiple
** arguments.
*/
Expr *sqlite3ExprFunction(
  Parse *pParse,        /* Parsing context */
  ExprList *pList,      /* Argument list */
  const Token *pToken,  /* Name of the function */
  int eDistinct         /* SF_Distinct or SF_ALL or 0 */
){
  Expr *pNew;
  sqlite3 *db = pParse->db;
  assert( pToken );
  pNew = sqlite3ExprAlloc(db, TK_FUNCTION, pToken, 1);
  if( pNew==0 ){
    sqlite3ExprListDelete(db, pList); /* Avoid memory leak when malloc fails */
    return 0;
  }
  assert( !ExprHasProperty(pNew, EP_InnerON|EP_OuterON) );
  pNew->w.iOfst = (int)(pToken->z - pParse->zTail);
  if( pList
   && pList->nExpr > pParse->db->aLimit[SQLITE_LIMIT_FUNCTION_ARG]
   && !pParse->nested
  ){
    sqlite3ErrorMsg(pParse, "too many arguments on function %T", pToken);
  }
  pNew->x.pList = pList;
  ExprSetProperty(pNew, EP_HasFunc);
  assert( ExprUseXList(pNew) );
  sqlite3ExprSetHeightAndFlags(pParse, pNew);
  if( eDistinct==SF_Distinct ) ExprSetProperty(pNew, EP_Distinct);
  return pNew;
}

/*
** Report an error when attempting to use an ORDER BY clause within
** the arguments of a non-aggregate function.
*/
void sqlite3ExprOrderByAggregateError(Parse *pParse, Expr *p){
  sqlite3ErrorMsg(pParse,
     "ORDER BY may not be used with non-aggregate %#T()", p
  );
}

/*
** Attach an ORDER BY clause to a function call.
**
**     functionname( arguments ORDER BY sortlist )
**     \_____________________/          \______/
**             pExpr                    pOrderBy
**
** The ORDER BY clause is inserted into a new Expr node of type TK_ORDER
** and added to the Expr.pLeft field of the parent TK_FUNCTION node.
*/
void sqlite3ExprAddFunctionOrderBy(
  Parse *pParse,        /* Parsing context */
  Expr *pExpr,          /* The function call to which ORDER BY is to be added */
  ExprList *pOrderBy    /* The ORDER BY clause to add */
){
  Expr *pOB;
  sqlite3 *db = pParse->db;
  if( NEVER(pOrderBy==0) ){
    assert( db->mallocFailed );
    return;
  }
  if( pExpr==0 ){
    assert( db->mallocFailed );
    sqlite3ExprListDelete(db, pOrderBy);
    return;
  }
  assert( pExpr->op==TK_FUNCTION );
  assert( pExpr->pLeft==0 );
  assert( ExprUseXList(pExpr) );
  if( pExpr->x.pList==0 || NEVER(pExpr->x.pList->nExpr==0) ){
    /* Ignore ORDER BY on zero-argument aggregates */
    sqlite3ParserAddCleanup(pParse, sqlite3ExprListDeleteGeneric, pOrderBy);
    return;
  }
  if( IsWindowFunc(pExpr) ){
    sqlite3ExprOrderByAggregateError(pParse, pExpr);
    sqlite3ExprListDelete(db, pOrderBy);
    return;
  }
  if( pOrderBy->nExpr>db->aLimit[SQLITE_LIMIT_COLUMN] ){
    sqlite3ErrorMsg(pParse, "too many terms in ORDER BY clause");
    sqlite3ExprListDelete(db, pOrderBy);
    return;
  }

  pOB = sqlite3ExprAlloc(db, TK_ORDER, 0, 0);
  if( pOB==0 ){
    sqlite3ExprListDelete(db, pOrderBy);
    return;
  }
  pOB->x.pList = pOrderBy;
  assert( ExprUseXList(pOB) );
  pExpr->pLeft = pOB;
  ExprSetProperty(pOB, EP_FullSize);
}

/*
** Check to see if a function is usable according to current access
** rules:
**
**    SQLITE_FUNC_DIRECT    -     Only usable from top-level SQL
**
**    SQLITE_FUNC_UNSAFE    -     Usable if TRUSTED_SCHEMA or from
**                                top-level SQL
**
** If the function is not usable, create an error.
*/
void sqlite3ExprFunctionUsable(
  Parse *pParse,         /* Parsing and code generating context */
  const Expr *pExpr,     /* The function invocation */
  const FuncDef *pDef    /* The function being invoked */
){
  assert( !IN_RENAME_OBJECT );
  assert( (pDef->funcFlags & (SQLITE_FUNC_DIRECT|SQLITE_FUNC_UNSAFE))!=0 );
  if( ExprHasProperty(pExpr, EP_FromDDL) 
   || pParse->prepFlags & SQLITE_PREPARE_FROM_DDL
  ){
    if( (pDef->funcFlags & SQLITE_FUNC_DIRECT)!=0
     || (pParse->db->flags & SQLITE_TrustedSchema)==0
    ){
      /* Functions prohibited in triggers and views if:
      **     (1) tagged with SQLITE_DIRECTONLY
      **     (2) not tagged with SQLITE_INNOCUOUS (which means it
      **         is tagged with SQLITE_FUNC_UNSAFE) and
      **         SQLITE_DBCONFIG_TRUSTED_SCHEMA is off (meaning
      **         that the schema is possibly tainted).
      */
      sqlite3ErrorMsg(pParse, "unsafe use of %#T()", pExpr);
    }
  }
}

/*
** Assign a variable number to an expression that encodes a wildcard
** in the original SQL statement. 
**
** Wildcards consisting of a single "?" are assigned the next sequential
** variable number.
**
** Wildcards of the form "?nnn" are assigned the number "nnn".  We make
** sure "nnn" is not too big to avoid a denial of service attack when
** the SQL statement comes from an external source.
**
** Wildcards of the form ":aaa", "@aaa", or "$aaa" are assigned the same number
** as the previous instance of the same wildcard.  Or if this is the first
** instance of the wildcard, the next sequential variable number is
** assigned.
*/
void sqlite3ExprAssignVarNumber(Parse *pParse, Expr *pExpr, u32 n){
  sqlite3 *db = pParse->db;
  const char *z;
  ynVar x;

  if( pExpr==0 ) return;
  assert( !ExprHasProperty(pExpr, EP_IntValue|EP_Reduced|EP_TokenOnly) );
  z = pExpr->u.zToken;
  assert( z!=0 );
  assert( z[0]!=0 );
  assert( n==(u32)sqlite3Strlen30(z) );
  if( z[1]==0 ){
    /* Wildcard of the form "?".  Assign the next variable number */
    assert( z[0]=='?' );
    x = (ynVar)(++pParse->nVar);
  }else{
    int doAdd = 0;
    if( z[0]=='?' ){
      /* Wildcard of the form "?nnn".  Convert "nnn" to an integer and
      ** use it as the variable number */
      i64 i;
      int bOk;
      if( n==2 ){ /*OPTIMIZATION-IF-TRUE*/
        i = z[1]-'0';  /* The common case of ?N for a single digit N */
        bOk = 1;
      }else{
        bOk = 0==sqlite3Atoi64(&z[1], &i, n-1, SQLITE_UTF8);
      }
      testcase( i==0 );
      testcase( i==1 );
      testcase( i==db->aLimit[SQLITE_LIMIT_VARIABLE_NUMBER]-1 );
      testcase( i==db->aLimit[SQLITE_LIMIT_VARIABLE_NUMBER] );
      if( bOk==0 || i<1 || i>db->aLimit[SQLITE_LIMIT_VARIABLE_NUMBER] ){
        sqlite3ErrorMsg(pParse, "variable number must be between ?1 and ?%d",
            db->aLimit[SQLITE_LIMIT_VARIABLE_NUMBER]);
        sqlite3RecordErrorOffsetOfExpr(pParse->db, pExpr);
        return;
      }
      x = (ynVar)i;
      if( x>pParse->nVar ){
        pParse->nVar = (int)x;
        doAdd = 1;
      }else if( sqlite3VListNumToName(pParse->pVList, x)==0 ){
        doAdd = 1;
      }
    }else{
      /* Wildcards like ":aaa", "$aaa" or "@aaa".  Reuse the same variable
      ** number as the prior appearance of the same name, or if the name
      ** has never appeared before, reuse the same variable number
      */
      x = (ynVar)sqlite3VListNameToNum(pParse->pVList, z, n);
      if( x==0 ){
        x = (ynVar)(++pParse->nVar);
        doAdd = 1;
      }
    }
    if( doAdd ){
      pParse->pVList = sqlite3VListAdd(db, pParse->pVList, z, n, x);
    }
  }
  pExpr->iColumn = x;
  if( x>db->aLimit[SQLITE_LIMIT_VARIABLE_NUMBER] ){
    sqlite3ErrorMsg(pParse, "too many SQL variables");
    sqlite3RecordErrorOffsetOfExpr(pParse->db, pExpr);
  }
}

/*
** Recursively delete an expression tree.
*/
static SQLITE_NOINLINE void sqlite3ExprDeleteNN(sqlite3 *db, Expr *p){
  assert( p!=0 );
  assert( db!=0 );
exprDeleteRestart:
  assert( !ExprUseUValue(p) || p->u.iValue>=0 );
  assert( !ExprUseYWin(p) || !ExprUseYSub(p) );
  assert( !ExprUseYWin(p) || p->y.pWin!=0 || db->mallocFailed );
  assert( p->op!=TK_FUNCTION || !ExprUseYSub(p) );
#ifdef SQLITE_DEBUG
  if( ExprHasProperty(p, EP_Leaf) && !ExprHasProperty(p, EP_TokenOnly) ){
    assert( p->pLeft==0 );
    assert( p->pRight==0 );
    assert( !ExprUseXSelect(p) || p->x.pSelect==0 );
    assert( !ExprUseXList(p) || p->x.pList==0 );
  }
#endif
  if( !ExprHasProperty(p, (EP_TokenOnly|EP_Leaf)) ){
    /* The Expr.x union is never used at the same time as Expr.pRight */
    assert( (ExprUseXList(p) && p->x.pList==0) || p->pRight==0 );
    if( p->pRight ){
      assert( !ExprHasProperty(p, EP_WinFunc) );
      sqlite3ExprDeleteNN(db, p->pRight);
    }else if( ExprUseXSelect(p) ){
      assert( !ExprHasProperty(p, EP_WinFunc) );
      sqlite3SelectDelete(db, p->x.pSelect);
    }else{
      sqlite3ExprListDelete(db, p->x.pList);
#ifndef SQLITE_OMIT_WINDOWFUNC
      if( ExprHasProperty(p, EP_WinFunc) ){
        sqlite3WindowDelete(db, p->y.pWin);
      }
#endif
    }
    if( p->pLeft && p->op!=TK_SELECT_COLUMN ){
      Expr *pLeft = p->pLeft;
      if( !ExprHasProperty(p, EP_Static)
       && !ExprHasProperty(pLeft, EP_Static)
      ){
        /* Avoid unnecessary recursion on unary operators */
        sqlite3DbNNFreeNN(db, p);
        p = pLeft;
        goto exprDeleteRestart;
      }else{
        sqlite3ExprDeleteNN(db, pLeft);
      }
    }
  }
  if( !ExprHasProperty(p, EP_Static) ){
    sqlite3DbNNFreeNN(db, p);
  }
}
void sqlite3ExprDelete(sqlite3 *db, Expr *p){
  if( p ) sqlite3ExprDeleteNN(db, p);
}
void sqlite3ExprDeleteGeneric(sqlite3 *db, void *p){
  if( ALWAYS(p) ) sqlite3ExprDeleteNN(db, (Expr*)p);
}

/*
** Clear both elements of an OnOrUsing object
*/
void sqlite3ClearOnOrUsing(sqlite3 *db, OnOrUsing *p){
  if( p==0 ){
    /* Nothing to clear */
  }else if( p->pOn ){
    sqlite3ExprDeleteNN(db, p->pOn);
  }else if( p->pUsing ){
    sqlite3IdListDelete(db, p->pUsing);
  }
}

/*
** Arrange to cause pExpr to be deleted when the pParse is deleted.
** This is similar to sqlite3ExprDelete() except that the delete is
** deferred until the pParse is deleted.
**
** The pExpr might be deleted immediately on an OOM error.
**
** Return 0 if the delete was successfully deferred.  Return non-zero
** if the delete happened immediately because of an OOM.
*/
int sqlite3ExprDeferredDelete(Parse *pParse, Expr *pExpr){
  return 0==sqlite3ParserAddCleanup(pParse, sqlite3ExprDeleteGeneric, pExpr);
}

/* Invoke sqlite3RenameExprUnmap() and sqlite3ExprDelete() on the
** expression.
*/
void sqlite3ExprUnmapAndDelete(Parse *pParse, Expr *p){
  if( p ){
    if( IN_RENAME_OBJECT ){
      sqlite3RenameExprUnmap(pParse, p);
    }
    sqlite3ExprDeleteNN(pParse->db, p);
  }
}

/*
** Return the number of bytes allocated for the expression structure
** passed as the first argument. This is always one of EXPR_FULLSIZE,
** EXPR_REDUCEDSIZE or EXPR_TOKENONLYSIZE.
*/
static int exprStructSize(const Expr *p){
  if( ExprHasProperty(p, EP_TokenOnly) ) return EXPR_TOKENONLYSIZE;
  if( ExprHasProperty(p, EP_Reduced) ) return EXPR_REDUCEDSIZE;
  return EXPR_FULLSIZE;
}

/*
** The dupedExpr*Size() routines each return the number of bytes required
** to store a copy of an expression or expression tree.  They differ in
** how much of the tree is measured.
**
**     dupedExprStructSize()     Size of only the Expr structure
**     dupedExprNodeSize()       Size of Expr + space for token
**     dupedExprSize()           Expr + token + subtree components
**
***************************************************************************
**
** The dupedExprStructSize() function returns two values OR-ed together: 
** (1) the space required for a copy of the Expr structure only and
** (2) the EP_xxx flags that indicate what the structure size should be.
** The return values is always one of:
**
**      EXPR_FULLSIZE
**      EXPR_REDUCEDSIZE   | EP_Reduced
**      EXPR_TOKENONLYSIZE | EP_TokenOnly
**
** The size of the structure can be found by masking the return value
** of this routine with 0xfff.  The flags can be found by masking the
** return value with EP_Reduced|EP_TokenOnly.
**
** Note that with flags==EXPRDUP_REDUCE, this routines works on full-size
** (unreduced) Expr objects as they or originally constructed by the parser.
** During expression analysis, extra information is computed and moved into
** later parts of the Expr object and that extra information might get chopped
** off if the expression is reduced.  Note also that it does not work to
** make an EXPRDUP_REDUCE copy of a reduced expression.  It is only legal
** to reduce a pristine expression tree from the parser.  The implementation
** of dupedExprStructSize() contain multiple assert() statements that attempt
** to enforce this constraint.
*/
static int dupedExprStructSize(const Expr *p, int flags){
  int nSize;
  assert( flags==EXPRDUP_REDUCE || flags==0 ); /* Only one flag value allowed */
  assert( EXPR_FULLSIZE<=0xfff );
  assert( (0xfff & (EP_Reduced|EP_TokenOnly))==0 );
  if( 0==flags || ExprHasProperty(p, EP_FullSize) ){
    nSize = EXPR_FULLSIZE;
  }else{
    assert( !ExprHasProperty(p, EP_TokenOnly|EP_Reduced) );
    assert( !ExprHasProperty(p, EP_OuterON) );
    assert( !ExprHasVVAProperty(p, EP_NoReduce) );
    if( p->pLeft || p->x.pList ){
      nSize = EXPR_REDUCEDSIZE | EP_Reduced;
    }else{
      assert( p->pRight==0 );
      nSize = EXPR_TOKENONLYSIZE | EP_TokenOnly;
    }
  }
  return nSize;
}

/*
** This function returns the space in bytes required to store the copy
** of the Expr structure and a copy of the Expr.u.zToken string (if that
** string is defined.)
*/
static int dupedExprNodeSize(const Expr *p, int flags){
  int nByte = dupedExprStructSize(p, flags) & 0xfff;
  if( !ExprHasProperty(p, EP_IntValue) && p->u.zToken ){
    nByte += sqlite3Strlen30NN(p->u.zToken)+1;
  }
  return ROUND8(nByte);
}

/*
** Return the number of bytes required to create a duplicate of the
** expression passed as the first argument.
**
** The value returned includes space to create a copy of the Expr struct
** itself and the buffer referred to by Expr.u.zToken, if any.
**
** The return value includes space to duplicate all Expr nodes in the
** tree formed by Expr.pLeft and Expr.pRight, but not any other
** substructure such as Expr.x.pList, Expr.x.pSelect, and Expr.y.pWin.
*/
static int dupedExprSize(const Expr *p){
  int nByte;
  assert( p!=0 );
  nByte = dupedExprNodeSize(p, EXPRDUP_REDUCE);
  if( p->pLeft ) nByte += dupedExprSize(p->pLeft);
  if( p->pRight ) nByte += dupedExprSize(p->pRight);
  assert( nByte==ROUND8(nByte) );
  return nByte;
}

/*
** An EdupBuf is a memory allocation used to stored multiple Expr objects
** together with their Expr.zToken content.  This is used to help implement
** compression while doing sqlite3ExprDup().  The top-level Expr does the
** allocation for itself and many of its decendents, then passes an instance
** of the structure down into exprDup() so that they decendents can have
** access to that memory.
*/
typedef struct EdupBuf EdupBuf;
struct EdupBuf {
  u8 *zAlloc;          /* Memory space available for storage */
#ifdef SQLITE_DEBUG
  u8 *zEnd;            /* First byte past the end of memory */
#endif
};

/*
** This function is similar to sqlite3ExprDup(), except that if pEdupBuf
** is not NULL then it points to memory that can be used to store a copy
** of the input Expr p together with its p->u.zToken (if any).  pEdupBuf
** is updated with the new buffer tail prior to returning.
*/
static Expr *exprDup(
  sqlite3 *db,          /* Database connection (for memory allocation) */
  const Expr *p,        /* Expr tree to be duplicated */
  int dupFlags,         /* EXPRDUP_REDUCE for compression.  0 if not */
  EdupBuf *pEdupBuf     /* Preallocated storage space, or NULL */
){
  Expr *pNew;           /* Value to return */
  EdupBuf sEdupBuf;     /* Memory space from which to build Expr object */
  u32 staticFlag;       /* EP_Static if space not obtained from malloc */
  int nToken = -1;       /* Space needed for p->u.zToken.  -1 means unknown */

  assert( db!=0 );
  assert( p );
  assert( dupFlags==0 || dupFlags==EXPRDUP_REDUCE );
  assert( pEdupBuf==0 || dupFlags==EXPRDUP_REDUCE );

  /* Figure out where to write the new Expr structure. */
  if( pEdupBuf ){
    sEdupBuf.zAlloc = pEdupBuf->zAlloc;
#ifdef SQLITE_DEBUG
    sEdupBuf.zEnd = pEdupBuf->zEnd;
#endif
    staticFlag = EP_Static;
    assert( sEdupBuf.zAlloc!=0 );
    assert( dupFlags==EXPRDUP_REDUCE );
  }else{
    int nAlloc;
    if( dupFlags ){
      nAlloc = dupedExprSize(p);
    }else if( !ExprHasProperty(p, EP_IntValue) && p->u.zToken ){
      nToken = sqlite3Strlen30NN(p->u.zToken)+1;
      nAlloc = ROUND8(EXPR_FULLSIZE + nToken);
    }else{
      nToken = 0;
      nAlloc = ROUND8(EXPR_FULLSIZE);
    }
    assert( nAlloc==ROUND8(nAlloc) );
    sEdupBuf.zAlloc = sqlite3DbMallocRawNN(db, nAlloc);
#ifdef SQLITE_DEBUG
    sEdupBuf.zEnd = sEdupBuf.zAlloc ? sEdupBuf.zAlloc+nAlloc : 0;
#endif
    
    staticFlag = 0;
  }
  pNew = (Expr *)sEdupBuf.zAlloc;
  assert( EIGHT_BYTE_ALIGNMENT(pNew) );

  if( pNew ){
    /* Set nNewSize to the size allocated for the structure pointed to
    ** by pNew. This is either EXPR_FULLSIZE, EXPR_REDUCEDSIZE or
    ** EXPR_TOKENONLYSIZE. nToken is set to the number of bytes consumed
    ** by the copy of the p->u.zToken string (if any).
    */
    const unsigned nStructSize = dupedExprStructSize(p, dupFlags);
    int nNewSize = nStructSize & 0xfff;
    if( nToken<0 ){
      if( !ExprHasProperty(p, EP_IntValue) && p->u.zToken ){
        nToken = sqlite3Strlen30(p->u.zToken) + 1;
      }else{
        nToken = 0;
      }
    }
    if( dupFlags ){
      assert( (int)(sEdupBuf.zEnd - sEdupBuf.zAlloc) >= nNewSize+nToken );
      assert( ExprHasProperty(p, EP_Reduced)==0 );
      memcpy(sEdupBuf.zAlloc, p, nNewSize);
    }else{
      u32 nSize = (u32)exprStructSize(p);
      assert( (int)(sEdupBuf.zEnd - sEdupBuf.zAlloc) >=
                                                   (int)EXPR_FULLSIZE+nToken );
      memcpy(sEdupBuf.zAlloc, p, nSize);
      if( nSize<EXPR_FULLSIZE ){
        memset(&sEdupBuf.zAlloc[nSize], 0, EXPR_FULLSIZE-nSize);
      }
      nNewSize = EXPR_FULLSIZE;
    }

    /* Set the EP_Reduced, EP_TokenOnly, and EP_Static flags appropriately. */
    pNew->flags &= ~(EP_Reduced|EP_TokenOnly|EP_Static);
    pNew->flags |= nStructSize & (EP_Reduced|EP_TokenOnly);
    pNew->flags |= staticFlag;
    ExprClearVVAProperties(pNew);
    if( dupFlags ){
      ExprSetVVAProperty(pNew, EP_Immutable);
    }

    /* Copy the p->u.zToken string, if any. */
    assert( nToken>=0 );
    if( nToken>0 ){
      char *zToken = pNew->u.zToken = (char*)&sEdupBuf.zAlloc[nNewSize];
      memcpy(zToken, p->u.zToken, nToken);
      nNewSize += nToken;
    }
    sEdupBuf.zAlloc += ROUND8(nNewSize);

    if( ((p->flags|pNew->flags)&(EP_TokenOnly|EP_Leaf))==0 ){

      /* Fill in the pNew->x.pSelect or pNew->x.pList member. */
      if( ExprUseXSelect(p) ){
        pNew->x.pSelect = sqlite3SelectDup(db, p->x.pSelect, dupFlags);
      }else{
        pNew->x.pList = sqlite3ExprListDup(db, p->x.pList,
                           p->op!=TK_ORDER ? dupFlags : 0);
      }

#ifndef SQLITE_OMIT_WINDOWFUNC
      if( ExprHasProperty(p, EP_WinFunc) ){
        pNew->y.pWin = sqlite3WindowDup(db, pNew, p->y.pWin);
        assert( ExprHasProperty(pNew, EP_WinFunc) );
      }
#endif /* SQLITE_OMIT_WINDOWFUNC */

      /* Fill in pNew->pLeft and pNew->pRight. */
      if( dupFlags ){
        if( p->op==TK_SELECT_COLUMN ){
          pNew->pLeft = p->pLeft;
          assert( p->pRight==0 
               || p->pRight==p->pLeft
               || ExprHasProperty(p->pLeft, EP_Subquery) );
        }else{
          pNew->pLeft = p->pLeft ?
                      exprDup(db, p->pLeft, EXPRDUP_REDUCE, &sEdupBuf) : 0;
        }
        pNew->pRight = p->pRight ?
                       exprDup(db, p->pRight, EXPRDUP_REDUCE, &sEdupBuf) : 0;
      }else{
        if( p->op==TK_SELECT_COLUMN ){
          pNew->pLeft = p->pLeft;
          assert( p->pRight==0 
               || p->pRight==p->pLeft
               || ExprHasProperty(p->pLeft, EP_Subquery) );
        }else{
          pNew->pLeft = sqlite3ExprDup(db, p->pLeft, 0);
        }
        pNew->pRight = sqlite3ExprDup(db, p->pRight, 0);
      }
    }
  }
  if( pEdupBuf ) memcpy(pEdupBuf, &sEdupBuf, sizeof(sEdupBuf));
  assert( sEdupBuf.zAlloc <= sEdupBuf.zEnd );
  return pNew;
}

/*
** Create and return a deep copy of the object passed as the second
** argument. If an OOM condition is encountered, NULL is returned
** and the db->mallocFailed flag set.
*/
#ifndef SQLITE_OMIT_CTE
With *sqlite3WithDup(sqlite3 *db, With *p){
  With *pRet = 0;
  if( p ){
    sqlite3_int64 nByte = SZ_WITH(p->nCte);
    pRet = sqlite3DbMallocZero(db, nByte);
    if( pRet ){
      int i;
      pRet->nCte = p->nCte;
      for(i=0; i<p->nCte; i++){
        pRet->a[i].pSelect = sqlite3SelectDup(db, p->a[i].pSelect, 0);
        pRet->a[i].pCols = sqlite3ExprListDup(db, p->a[i].pCols, 0);
        pRet->a[i].zName = sqlite3DbStrDup(db, p->a[i].zName);
        pRet->a[i].eM10d = p->a[i].eM10d;
      }
    }
  }
  return pRet;
}
#else
# define sqlite3WithDup(x,y) 0
#endif

#ifndef SQLITE_OMIT_WINDOWFUNC
/*
** The gatherSelectWindows() procedure and its helper routine
** gatherSelectWindowsCallback() are used to scan all the expressions
** an a newly duplicated SELECT statement and gather all of the Window
** objects found there, assembling them onto the linked list at Select->pWin.
*/
static int gatherSelectWindowsCallback(Walker *pWalker, Expr *pExpr){
  if( pExpr->op==TK_FUNCTION && ExprHasProperty(pExpr, EP_WinFunc) ){
    Select *pSelect = pWalker->u.pSelect;
    Window *pWin = pExpr->y.pWin;
    assert( pWin );
    assert( IsWindowFunc(pExpr) );
    assert( pWin->ppThis==0 );
    sqlite3WindowLink(pSelect, pWin);
  }
  return WRC_Continue;
}
static int gatherSelectWindowsSelectCallback(Walker *pWalker, Select *p){
  return p==pWalker->u.pSelect ? WRC_Continue : WRC_Prune;
}
static void gatherSelectWindows(Select *p){
  Walker w;
  w.xExprCallback = gatherSelectWindowsCallback;
  w.xSelectCallback = gatherSelectWindowsSelectCallback;
  w.xSelectCallback2 = 0;
  w.pParse = 0;
  w.u.pSelect = p;
  sqlite3WalkSelect(&w, p);
}
#endif


/*
** The following group of routines make deep copies of expressions,
** expression lists, ID lists, and select statements.  The copies can
** be deleted (by being passed to their respective ...Delete() routines)
** without effecting the originals.
**
** The expression list, ID, and source lists return by sqlite3ExprListDup(),
** sqlite3IdListDup(), and sqlite3SrcListDup() can not be further expanded
** by subsequent calls to sqlite*ListAppend() routines.
**
** Any tables that the SrcList might point to are not duplicated.
**
** The flags parameter contains a combination of the EXPRDUP_XXX flags.
** If the EXPRDUP_REDUCE flag is set, then the structure returned is a
** truncated version of the usual Expr structure that will be stored as
** part of the in-memory representation of the database schema.
*/
Expr *sqlite3ExprDup(sqlite3 *db, const Expr *p, int flags){
  assert( flags==0 || flags==EXPRDUP_REDUCE );
  return p ? exprDup(db, p, flags, 0) : 0;
}
ExprList *sqlite3ExprListDup(sqlite3 *db, const ExprList *p, int flags){
  ExprList *pNew;
  struct ExprList_item *pItem;
  const struct ExprList_item *pOldItem;
  int i;
  Expr *pPriorSelectColOld = 0;
  Expr *pPriorSelectColNew = 0;
  assert( db!=0 );
  if( p==0 ) return 0;
  pNew = sqlite3DbMallocRawNN(db, sqlite3DbMallocSize(db, p));
  if( pNew==0 ) return 0;
  pNew->nExpr = p->nExpr;
  pNew->nAlloc = p->nAlloc;
  pItem = pNew->a;
  pOldItem = p->a;
  for(i=0; i<p->nExpr; i++, pItem++, pOldItem++){
    Expr *pOldExpr = pOldItem->pExpr;
    Expr *pNewExpr;
    pItem->pExpr = sqlite3ExprDup(db, pOldExpr, flags);
    if( pOldExpr
     && pOldExpr->op==TK_SELECT_COLUMN
     && (pNewExpr = pItem->pExpr)!=0
    ){
      if( pNewExpr->pRight ){
        pPriorSelectColOld = pOldExpr->pRight;
        pPriorSelectColNew = pNewExpr->pRight;
        pNewExpr->pLeft = pNewExpr->pRight;
      }else{
        if( pOldExpr->pLeft!=pPriorSelectColOld ){
          pPriorSelectColOld = pOldExpr->pLeft;
          pPriorSelectColNew = sqlite3ExprDup(db, pPriorSelectColOld, flags);
          pNewExpr->pRight = pPriorSelectColNew;
        }
        pNewExpr->pLeft = pPriorSelectColNew;
      }
    }
    pItem->zEName = sqlite3DbStrDup(db, pOldItem->zEName);
    pItem->fg = pOldItem->fg;
    pItem->u = pOldItem->u;
  }
  return pNew;
}

/*
** If cursors, triggers, views and subqueries are all omitted from
** the build, then none of the following routines, except for
** sqlite3SelectDup(), can be called. sqlite3SelectDup() is sometimes
** called with a NULL argument.
*/
#if !defined(SQLITE_OMIT_VIEW) || !defined(SQLITE_OMIT_TRIGGER) \
 || !defined(SQLITE_OMIT_SUBQUERY)
SrcList *sqlite3SrcListDup(sqlite3 *db, const SrcList *p, int flags){
  SrcList *pNew;
  int i;
  assert( db!=0 );
  if( p==0 ) return 0;
  pNew = sqlite3DbMallocRawNN(db, SZ_SRCLIST(p->nSrc) );
  if( pNew==0 ) return 0;
  pNew->nSrc = pNew->nAlloc = p->nSrc;
  for(i=0; i<p->nSrc; i++){
    SrcItem *pNewItem = &pNew->a[i];
    const SrcItem *pOldItem = &p->a[i];
    Table *pTab;
    pNewItem->fg = pOldItem->fg;
    if( pOldItem->fg.isSubquery ){
      Subquery *pNewSubq = sqlite3DbMallocRaw(db, sizeof(Subquery));
      if( pNewSubq==0 ){
        assert( db->mallocFailed );
        pNewItem->fg.isSubquery = 0;
      }else{
        memcpy(pNewSubq, pOldItem->u4.pSubq, sizeof(*pNewSubq));
        pNewSubq->pSelect = sqlite3SelectDup(db, pNewSubq->pSelect, flags);
        if( pNewSubq->pSelect==0 ){
          sqlite3DbFree(db, pNewSubq);
          pNewSubq = 0;
          pNewItem->fg.isSubquery = 0;
        }
      }
      pNewItem->u4.pSubq = pNewSubq;
    }else if( pOldItem->fg.fixedSchema ){
      pNewItem->u4.pSchema = pOldItem->u4.pSchema;
    }else{
      pNewItem->u4.zDatabase = sqlite3DbStrDup(db, pOldItem->u4.zDatabase);
    }
    pNewItem->zName = sqlite3DbStrDup(db, pOldItem->zName);
    pNewItem->zAlias = sqlite3DbStrDup(db, pOldItem->zAlias);
    pNewItem->iCursor = pOldItem->iCursor;
    if( pNewItem->fg.isIndexedBy ){
      pNewItem->u1.zIndexedBy = sqlite3DbStrDup(db, pOldItem->u1.zIndexedBy);
    }else if( pNewItem->fg.isTabFunc ){
      pNewItem->u1.pFuncArg =
          sqlite3ExprListDup(db, pOldItem->u1.pFuncArg, flags);
    }else{
      pNewItem->u1.nRow = pOldItem->u1.nRow;
    }
    pNewItem->u2 = pOldItem->u2;
    if( pNewItem->fg.isCte ){
      pNewItem->u2.pCteUse->nUse++;
    }
    pTab = pNewItem->pSTab = pOldItem->pSTab;
    if( pTab ){
      pTab->nTabRef++;
    }
    if( pOldItem->fg.isUsing ){
      assert( pNewItem->fg.isUsing );
      pNewItem->u3.pUsing = sqlite3IdListDup(db, pOldItem->u3.pUsing);
    }else{
      pNewItem->u3.pOn = sqlite3ExprDup(db, pOldItem->u3.pOn, flags);
    }
    pNewItem->colUsed = pOldItem->colUsed;
  }
  return pNew;
}
IdList *sqlite3IdListDup(sqlite3 *db, const IdList *p){
  IdList *pNew;
  int i;
  assert( db!=0 );
  if( p==0 ) return 0;
  pNew = sqlite3DbMallocRawNN(db, SZ_IDLIST(p->nId));
  if( pNew==0 ) return 0;
  pNew->nId = p->nId;
  for(i=0; i<p->nId; i++){
    struct IdList_item *pNewItem = &pNew->a[i];
    const struct IdList_item *pOldItem = &p->a[i];
    pNewItem->zName = sqlite3DbStrDup(db, pOldItem->zName);
  }
  return pNew;
}
Select *sqlite3SelectDup(sqlite3 *db, const Select *pDup, int flags){
  Select *pRet = 0;
  Select *pNext = 0;
  Select **pp = &pRet;
  const Select *p;

  assert( db!=0 );
  for(p=pDup; p; p=p->pPrior){
    Select *pNew = sqlite3DbMallocRawNN(db, sizeof(*p) );
    if( pNew==0 ) break;
    pNew->pEList = sqlite3ExprListDup(db, p->pEList, flags);
    pNew->pSrc = sqlite3SrcListDup(db, p->pSrc, flags);
    pNew->pWhere = sqlite3ExprDup(db, p->pWhere, flags);
    pNew->pGroupBy = sqlite3ExprListDup(db, p->pGroupBy, flags);
    pNew->pHaving = sqlite3ExprDup(db, p->pHaving, flags);
    pNew->pOrderBy = sqlite3ExprListDup(db, p->pOrderBy, flags);
    pNew->op = p->op;
    pNew->pNext = pNext;
    pNew->pPrior = 0;
    pNew->pLimit = sqlite3ExprDup(db, p->pLimit, flags);
    pNew->iLimit = 0;
    pNew->iOffset = 0;
    pNew->selFlags = p->selFlags;
    pNew->nSelectRow = p->nSelectRow;
    pNew->pWith = sqlite3WithDup(db, p->pWith);
#ifndef SQLITE_OMIT_WINDOWFUNC
    pNew->pWin = 0;
    pNew->pWinDefn = sqlite3WindowListDup(db, p->pWinDefn);
    if( p->pWin && db->mallocFailed==0 ) gatherSelectWindows(pNew);
#endif
    pNew->selId = p->selId;
    if( db->mallocFailed ){
      /* Any prior OOM might have left the Select object incomplete.
      ** Delete the whole thing rather than allow an incomplete Select
      ** to be used by the code generator. */
      pNew->pNext = 0;
      sqlite3SelectDelete(db, pNew);
      break;
    }
    *pp = pNew;
    pp = &pNew->pPrior;
    pNext = pNew;
  }
  return pRet;
}
#else
Select *sqlite3SelectDup(sqlite3 *db, const Select *p, int flags){
  assert( p==0 );
  return 0;
}
#endif


/*
** Add a new element to the end of an expression list.  If pList is
** initially NULL, then create a new expression list.
**
** The pList argument must be either NULL or a pointer to an ExprList
** obtained from a prior call to sqlite3ExprListAppend().
**
** If a memory allocation error occurs, the entire list is freed and
** NULL is returned.  If non-NULL is returned, then it is guaranteed
** that the new entry was successfully appended.
*/
static const struct ExprList_item zeroItem = {0};
SQLITE_NOINLINE ExprList *sqlite3ExprListAppendNew(
  sqlite3 *db,            /* Database handle.  Used for memory allocation */
  Expr *pExpr             /* Expression to be appended. Might be NULL */
){
  struct ExprList_item *pItem;
  ExprList *pList;

  pList = sqlite3DbMallocRawNN(db, SZ_EXPRLIST(4));
  if( pList==0 ){
    sqlite3ExprDelete(db, pExpr);
    return 0;
  }
  pList->nAlloc = 4;
  pList->nExpr = 1;
  pItem = &pList->a[0];
  *pItem = zeroItem;
  pItem->pExpr = pExpr;
  return pList;
}
SQLITE_NOINLINE ExprList *sqlite3ExprListAppendGrow(
  sqlite3 *db,            /* Database handle.  Used for memory allocation */
  ExprList *pList,        /* List to which to append. Might be NULL */
  Expr *pExpr             /* Expression to be appended. Might be NULL */
){
  struct ExprList_item *pItem;
  ExprList *pNew;
  pList->nAlloc *= 2;
  pNew = sqlite3DbRealloc(db, pList, SZ_EXPRLIST(pList->nAlloc));
  if( pNew==0 ){
    sqlite3ExprListDelete(db, pList);
    sqlite3ExprDelete(db, pExpr);
    return 0;
  }else{
    pList = pNew;
  }
  pItem = &pList->a[pList->nExpr++];
  *pItem = zeroItem;
  pItem->pExpr = pExpr;
  return pList;
}
ExprList *sqlite3ExprListAppend(
  Parse *pParse,          /* Parsing context */
  ExprList *pList,        /* List to which to append. Might be NULL */
  Expr *pExpr             /* Expression to be appended. Might be NULL */
){
  struct ExprList_item *pItem;
  if( pList==0 ){
    return sqlite3ExprListAppendNew(pParse->db,pExpr);
  }
  if( pList->nAlloc<pList->nExpr+1 ){
    return sqlite3ExprListAppendGrow(pParse->db,pList,pExpr);
  }
  pItem = &pList->a[pList->nExpr++];
  *pItem = zeroItem;
  pItem->pExpr = pExpr;
  return pList;
}

/*
** pColumns and pExpr form a vector assignment which is part of the SET
** clause of an UPDATE statement.  Like this:
**
**        (a,b,c) = (expr1,expr2,expr3)
** Or:    (a,b,c) = (SELECT x,y,z FROM ....)
**
** For each term of the vector assignment, append new entries to the
** expression list pList.  In the case of a subquery on the RHS, append
** TK_SELECT_COLUMN expressions.
*/
ExprList *sqlite3ExprListAppendVector(
  Parse *pParse,         /* Parsing context */
  ExprList *pList,       /* List to which to append. Might be NULL */
  IdList *pColumns,      /* List of names of LHS of the assignment */
  Expr *pExpr            /* Vector expression to be appended. Might be NULL */
){
  sqlite3 *db = pParse->db;
  int n;
  int i;
  int iFirst = pList ? pList->nExpr : 0;
  /* pColumns can only be NULL due to an OOM but an OOM will cause an
  ** exit prior to this routine being invoked */
  if( NEVER(pColumns==0) ) goto vector_append_error;
  if( pExpr==0 ) goto vector_append_error;

  /* If the RHS is a vector, then we can immediately check to see that
  ** the size of the RHS and LHS match.  But if the RHS is a SELECT,
  ** wildcards ("*") in the result set of the SELECT must be expanded before
  ** we can do the size check, so defer the size check until code generation.
  */
  if( pExpr->op!=TK_SELECT && pColumns->nId!=(n=sqlite3ExprVectorSize(pExpr)) ){
    sqlite3ErrorMsg(pParse, "%d columns assigned %d values",
                    pColumns->nId, n);
    goto vector_append_error;
  }

  for(i=0; i<pColumns->nId; i++){
    Expr *pSubExpr = sqlite3ExprForVectorField(pParse, pExpr, i, pColumns->nId);
    assert( pSubExpr!=0 || db->mallocFailed );
    if( pSubExpr==0 ) continue;
    pList = sqlite3ExprListAppend(pParse, pList, pSubExpr);
    if( pList ){
      assert( pList->nExpr==iFirst+i+1 );
      pList->a[pList->nExpr-1].zEName = pColumns->a[i].zName;
      pColumns->a[i].zName = 0;
    }
  }

  if( !db->mallocFailed && pExpr->op==TK_SELECT && ALWAYS(pList!=0) ){
    Expr *pFirst = pList->a[iFirst].pExpr;
    assert( pFirst!=0 );
    assert( pFirst->op==TK_SELECT_COLUMN );
    
    /* Store the SELECT statement in pRight so it will be deleted when
    ** sqlite3ExprListDelete() is called */
    pFirst->pRight = pExpr;
    pExpr = 0;

    /* Remember the size of the LHS in iTable so that we can check that
    ** the RHS and LHS sizes match during code generation. */
    pFirst->iTable = pColumns->nId;
  }

vector_append_error:
  sqlite3ExprUnmapAndDelete(pParse, pExpr);
  sqlite3IdListDelete(db, pColumns);
  return pList;
}

/*
** Set the sort order for the last element on the given ExprList.
*/
void sqlite3ExprListSetSortOrder(ExprList *p, int iSortOrder, int eNulls){
  struct ExprList_item *pItem;
  if( p==0 ) return;
  assert( p->nExpr>0 );

  assert( SQLITE_SO_UNDEFINED<0 && SQLITE_SO_ASC==0 && SQLITE_SO_DESC>0 );
  assert( iSortOrder==SQLITE_SO_UNDEFINED
       || iSortOrder==SQLITE_SO_ASC
       || iSortOrder==SQLITE_SO_DESC
  );
  assert( eNulls==SQLITE_SO_UNDEFINED
       || eNulls==SQLITE_SO_ASC
       || eNulls==SQLITE_SO_DESC
  );

  pItem = &p->a[p->nExpr-1];
  assert( pItem->fg.bNulls==0 );
  if( iSortOrder==SQLITE_SO_UNDEFINED ){
    iSortOrder = SQLITE_SO_ASC;
  }
  pItem->fg.sortFlags = (u8)iSortOrder;

  if( eNulls!=SQLITE_SO_UNDEFINED ){
    pItem->fg.bNulls = 1;
    if( iSortOrder!=eNulls ){
      pItem->fg.sortFlags |= KEYINFO_ORDER_BIGNULL;
    }
  }
}

/*
** Set the ExprList.a[].zEName element of the most recently added item
** on the expression list.
**
** pList might be NULL following an OOM error.  But pName should never be
** NULL.  If a memory allocation fails, the pParse->db->mallocFailed flag
** is set.
*/
void sqlite3ExprListSetName(
  Parse *pParse,          /* Parsing context */
  ExprList *pList,        /* List to which to add the span. */
  const Token *pName,     /* Name to be added */
  int dequote             /* True to cause the name to be dequoted */
){
  assert( pList!=0 || pParse->db->mallocFailed!=0 );
  assert( pParse->eParseMode!=PARSE_MODE_UNMAP || dequote==0 );
  if( pList ){
    struct ExprList_item *pItem;
    assert( pList->nExpr>0 );
    pItem = &pList->a[pList->nExpr-1];
    assert( pItem->zEName==0 );
    assert( pItem->fg.eEName==ENAME_NAME );
    pItem->zEName = sqlite3DbStrNDup(pParse->db, pName->z, pName->n);
    if( dequote ){
      /* If dequote==0, then pName->z does not point to part of a DDL
      ** statement handled by the parser. And so no token need be added
      ** to the token-map.  */
      sqlite3Dequote(pItem->zEName);
      if( IN_RENAME_OBJECT ){
        sqlite3RenameTokenMap(pParse, (const void*)pItem->zEName, pName);
      }
    }
  }
}

/*
** Set the ExprList.a[].zSpan element of the most recently added item
** on the expression list.
**
** pList might be NULL following an OOM error.  But pSpan should never be
** NULL.  If a memory allocation fails, the pParse->db->mallocFailed flag
** is set.
*/
void sqlite3ExprListSetSpan(
  Parse *pParse,          /* Parsing context */
  ExprList *pList,        /* List to which to add the span. */
  const char *zStart,     /* Start of the span */
  const char *zEnd        /* End of the span */
){
  sqlite3 *db = pParse->db;
  assert( pList!=0 || db->mallocFailed!=0 );
  if( pList ){
    struct ExprList_item *pItem = &pList->a[pList->nExpr-1];
    assert( pList->nExpr>0 );
    if( pItem->zEName==0 ){
      pItem->zEName = sqlite3DbSpanDup(db, zStart, zEnd);
      pItem->fg.eEName = ENAME_SPAN;
    }
  }
}

/*
** If the expression list pEList contains more than iLimit elements,
** leave an error message in pParse.
*/
void sqlite3ExprListCheckLength(
  Parse *pParse,
  ExprList *pEList,
  const char *zObject
){
  int mx = pParse->db->aLimit[SQLITE_LIMIT_COLUMN];
  testcase( pEList && pEList->nExpr==mx );
  testcase( pEList && pEList->nExpr==mx+1 );
  if( pEList && pEList->nExpr>mx ){
    sqlite3ErrorMsg(pParse, "too many columns in %s", zObject);
  }
}

/*
** Delete an entire expression list.
*/
static SQLITE_NOINLINE void exprListDeleteNN(sqlite3 *db, ExprList *pList){
  int i = pList->nExpr;
  struct ExprList_item *pItem =  pList->a;
  assert( pList->nExpr>0 );
  assert( db!=0 );
  do{
    sqlite3ExprDelete(db, pItem->pExpr);
    if( pItem->zEName ) sqlite3DbNNFreeNN(db, pItem->zEName);
    pItem++;
  }while( --i>0 );
  sqlite3DbNNFreeNN(db, pList);
}
void sqlite3ExprListDelete(sqlite3 *db, ExprList *pList){
  if( pList ) exprListDeleteNN(db, pList);
}
void sqlite3ExprListDeleteGeneric(sqlite3 *db, void *pList){
  if( ALWAYS(pList) ) exprListDeleteNN(db, (ExprList*)pList);
}

/*
** Return the bitwise-OR of all Expr.flags fields in the given
** ExprList.
*/
u32 sqlite3ExprListFlags(const ExprList *pList){
  int i;
  u32 m = 0;
  assert( pList!=0 );
  for(i=0; i<pList->nExpr; i++){
     Expr *pExpr = pList->a[i].pExpr;
     assert( pExpr!=0 );
     m |= pExpr->flags;
  }
  return m;
}

/*
** This is a SELECT-node callback for the expression walker that
** always "fails".  By "fail" in this case, we mean set
** pWalker->eCode to zero and abort.
**
** This callback is used by multiple expression walkers.
*/
int sqlite3SelectWalkFail(Walker *pWalker, Select *NotUsed){
  UNUSED_PARAMETER(NotUsed);
  pWalker->eCode = 0;
  return WRC_Abort;
}

/*
** Check the input string to see if it is "true" or "false" (in any case).
**
**       If the string is....           Return
**         "true"                         EP_IsTrue
**         "false"                        EP_IsFalse
**         anything else                  0
*/
u32 sqlite3IsTrueOrFalse(const char *zIn){
  if( sqlite3StrICmp(zIn, "true")==0  ) return EP_IsTrue;
  if( sqlite3StrICmp(zIn, "false")==0 ) return EP_IsFalse;
  return 0;
}


/*
** If the input expression is an ID with the name "true" or "false"
** then convert it into an TK_TRUEFALSE term.  Return non-zero if
** the conversion happened, and zero if the expression is unaltered.
*/
int sqlite3ExprIdToTrueFalse(Expr *pExpr){
  u32 v;
  assert( pExpr->op==TK_ID || pExpr->op==TK_STRING );
  if( !ExprHasProperty(pExpr, EP_Quoted|EP_IntValue)
   && (v = sqlite3IsTrueOrFalse(pExpr->u.zToken))!=0
  ){
    pExpr->op = TK_TRUEFALSE;
    ExprSetProperty(pExpr, v);
    return 1;
  }
  return 0;
}

/*
** The argument must be a TK_TRUEFALSE Expr node.  Return 1 if it is TRUE
** and 0 if it is FALSE.
*/
int sqlite3ExprTruthValue(const Expr *pExpr){
  pExpr = sqlite3ExprSkipCollateAndLikely((Expr*)pExpr);
  assert( pExpr->op==TK_TRUEFALSE );
  assert( !ExprHasProperty(pExpr, EP_IntValue) );
  assert( sqlite3StrICmp(pExpr->u.zToken,"true")==0
       || sqlite3StrICmp(pExpr->u.zToken,"false")==0 );
  return pExpr->u.zToken[4]==0;
}

/*
** If pExpr is an AND or OR expression, try to simplify it by eliminating
** terms that are always true or false.  Return the simplified expression.
** Or return the original expression if no simplification is possible.
**
** Examples:
**
**     (x<10) AND true                =>   (x<10)
**     (x<10) AND false               =>   false
**     (x<10) AND (y=22 OR false)     =>   (x<10) AND (y=22)
**     (x<10) AND (y=22 OR true)      =>   (x<10)
**     (y=22) OR true                 =>   true
*/
Expr *sqlite3ExprSimplifiedAndOr(Expr *pExpr){
  assert( pExpr!=0 );
  if( pExpr->op==TK_AND || pExpr->op==TK_OR ){
    Expr *pRight = sqlite3ExprSimplifiedAndOr(pExpr->pRight);
    Expr *pLeft = sqlite3ExprSimplifiedAndOr(pExpr->pLeft);
    if( ExprAlwaysTrue(pLeft) || ExprAlwaysFalse(pRight) ){
      pExpr = pExpr->op==TK_AND ? pRight : pLeft;
    }else if( ExprAlwaysTrue(pRight) || ExprAlwaysFalse(pLeft) ){
      pExpr = pExpr->op==TK_AND ? pLeft : pRight;
    }
  }
  return pExpr;
}

/*
** Return true if it might be advantageous to compute the right operand
** of expression pExpr first, before the left operand.
**
** Normally the left operand is computed before the right operand.  But if
** the left operand contains a subquery and the right does not, then it
** might be more efficient to compute the right operand first.
*/
static int exprEvalRhsFirst(Expr *pExpr){
  if( ExprHasProperty(pExpr->pLeft, EP_Subquery)
   && !ExprHasProperty(pExpr->pRight, EP_Subquery)
  ){
    return 1;
  }else{
    return 0;
  }
}

/*
** Compute the two operands of a binary operator.
**
** If either operand contains a subquery, then the code strives to
** compute the operand containing the subquery second.  If the other
** operand evalutes to NULL, then a jump is made.  The address of the
** IsNull operand that does this jump is returned.  The caller can use
** this to optimize the computation so as to avoid doing the potentially
** expensive subquery.
**
** If no optimization opportunities exist, return 0.
*/
static int exprComputeOperands(
  Parse *pParse,     /* Parsing context */
  Expr *pExpr,       /* The comparison expression */
  int *pR1,          /* OUT: Register holding the left operand */
  int *pR2,          /* OUT: Register holding the right operand */
  int *pFree1,       /* OUT: Temp register to free if not zero */
  int *pFree2        /* OUT: Another temp register to free if not zero */
){
  int addrIsNull;
  int r1, r2;
  Vdbe *v = pParse->pVdbe;

  assert( v!=0 );
  /*
  ** If the left operand contains a (possibly expensive) subquery and the
  ** right operand does not and the right operation might be NULL,
  ** then compute the right operand first and do an IsNull jump if the
  ** right operand evalutes to NULL.
  */
  if( exprEvalRhsFirst(pExpr) && sqlite3ExprCanBeNull(pExpr->pRight) ){
    r2 = sqlite3ExprCodeTemp(pParse, pExpr->pRight, pFree2);
    addrIsNull = sqlite3VdbeAddOp1(v, OP_IsNull, r2);
    VdbeComment((v, "skip left operand"));
    VdbeCoverage(v);
  }else{
    r2 = 0; /* Silence a false-positive uninit-var warning in MSVC */
    addrIsNull = 0;
  }
  r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, pFree1);
  if( addrIsNull==0 ){
    /*
    ** If the right operand contains a subquery and the left operand does not
    ** and the left operand might be NULL, then do an IsNull check
    ** check on the left operand before computing the right operand.
    */
    if( ExprHasProperty(pExpr->pRight, EP_Subquery)
     && sqlite3ExprCanBeNull(pExpr->pLeft)
    ){
      addrIsNull = sqlite3VdbeAddOp1(v, OP_IsNull, r1);
      VdbeComment((v, "skip right operand"));
      VdbeCoverage(v);
    }
    r2 = sqlite3ExprCodeTemp(pParse, pExpr->pRight, pFree2);
  }
  *pR1 = r1;
  *pR2 = r2;
  return addrIsNull;
}

/*
** pExpr is a TK_FUNCTION node.  Try to determine whether or not the
** function is a constant function.  A function is constant if all of
** the following are true:
**
**    (1)  It is a scalar function (not an aggregate or window function)
**    (2)  It has either the SQLITE_FUNC_CONSTANT or SQLITE_FUNC_SLOCHNG
**         property.
**    (3)  All of its arguments are constants
**
** This routine sets pWalker->eCode to 0 if pExpr is not a constant.
** It makes no changes to pWalker->eCode if pExpr is constant.  In
** every case, it returns WRC_Abort.
**
** Called as a service subroutine from exprNodeIsConstant().
*/
static SQLITE_NOINLINE int exprNodeIsConstantFunction(
  Walker *pWalker,
  Expr *pExpr
){
  int n;             /* Number of arguments */
  ExprList *pList;   /* List of arguments */
  FuncDef *pDef;     /* The function */
  sqlite3 *db;       /* The database */

  assert( pExpr->op==TK_FUNCTION );
  if( ExprHasProperty(pExpr, EP_TokenOnly)
   || (pList = pExpr->x.pList)==0
  ){;
    n = 0;
  }else{
    n = pList->nExpr;
    sqlite3WalkExprList(pWalker, pList);
    if( pWalker->eCode==0 ) return WRC_Abort;
  }
  db = pWalker->pParse->db;
  pDef = sqlite3FindFunction(db, pExpr->u.zToken, n, ENC(db), 0);
  if( pDef==0
   || pDef->xFinalize!=0
   || (pDef->funcFlags & (SQLITE_FUNC_CONSTANT|SQLITE_FUNC_SLOCHNG))==0
   || ExprHasProperty(pExpr, EP_WinFunc)
  ){
    pWalker->eCode = 0;
    return WRC_Abort;
  }
  return WRC_Prune;
}


/*
** These routines are Walker callbacks used to check expressions to
** see if they are "constant" for some definition of constant.  The
** Walker.eCode value determines the type of "constant" we are looking
** for.
**
** These callback routines are used to implement the following:
**
**     sqlite3ExprIsConstant()                  pWalker->eCode==1
**     sqlite3ExprIsConstantNotJoin()           pWalker->eCode==2
**     sqlite3ExprIsTableConstant()             pWalker->eCode==3
**     sqlite3ExprIsConstantOrFunction()        pWalker->eCode==4 or 5
**
** In all cases, the callbacks set Walker.eCode=0 and abort if the expression
** is found to not be a constant.
**
** The sqlite3ExprIsConstantOrFunction() is used for evaluating DEFAULT
** expressions in a CREATE TABLE statement.  The Walker.eCode value is 5
** when parsing an existing schema out of the sqlite_schema table and 4
** when processing a new CREATE TABLE statement.  A bound parameter raises
** an error for new statements, but is silently converted
** to NULL for existing schemas.  This allows sqlite_schema tables that
** contain a bound parameter because they were generated by older versions
** of SQLite to be parsed by newer versions of SQLite without raising a
** malformed schema error.
*/
static int exprNodeIsConstant(Walker *pWalker, Expr *pExpr){
  assert( pWalker->eCode>0 );

  /* If pWalker->eCode is 2 then any term of the expression that comes from
  ** the ON or USING clauses of an outer join disqualifies the expression
  ** from being considered constant. */
  if( pWalker->eCode==2 && ExprHasProperty(pExpr, EP_OuterON) ){
    pWalker->eCode = 0;
    return WRC_Abort;
  }

  switch( pExpr->op ){
    /* Consider functions to be constant if all their arguments are constant
    ** and either pWalker->eCode==4 or 5 or the function has the
    ** SQLITE_FUNC_CONST flag. */
    case TK_FUNCTION:
      if( (pWalker->eCode>=4 || ExprHasProperty(pExpr,EP_ConstFunc))
       && !ExprHasProperty(pExpr, EP_WinFunc)
      ){
        if( pWalker->eCode==5 ) ExprSetProperty(pExpr, EP_FromDDL);
        return WRC_Continue;
      }else if( pWalker->pParse ){
        return exprNodeIsConstantFunction(pWalker, pExpr);
      }else{
        pWalker->eCode = 0;
        return WRC_Abort;
      }
    case TK_ID:
      /* Convert "true" or "false" in a DEFAULT clause into the
      ** appropriate TK_TRUEFALSE operator */
      if( sqlite3ExprIdToTrueFalse(pExpr) ){
        return WRC_Prune;
      }
      /* no break */ deliberate_fall_through
    case TK_COLUMN:
    case TK_AGG_FUNCTION:
    case TK_AGG_COLUMN:
      testcase( pExpr->op==TK_ID );
      testcase( pExpr->op==TK_COLUMN );
      testcase( pExpr->op==TK_AGG_FUNCTION );
      testcase( pExpr->op==TK_AGG_COLUMN );
      if( ExprHasProperty(pExpr, EP_FixedCol) && pWalker->eCode!=2 ){
        return WRC_Continue;
      }
      if( pWalker->eCode==3 && pExpr->iTable==pWalker->u.iCur ){
        return WRC_Continue;
      }
      /* no break */ deliberate_fall_through
    case TK_IF_NULL_ROW:
    case TK_REGISTER:
    case TK_DOT:
    case TK_RAISE:
      testcase( pExpr->op==TK_REGISTER );
      testcase( pExpr->op==TK_IF_NULL_ROW );
      testcase( pExpr->op==TK_DOT );
      testcase( pExpr->op==TK_RAISE );
      pWalker->eCode = 0;
      return WRC_Abort;
    case TK_VARIABLE:
      if( pWalker->eCode==5 ){
        /* Silently convert bound parameters that appear inside of CREATE
        ** statements into a NULL when parsing the CREATE statement text out
        ** of the sqlite_schema table */
        pExpr->op = TK_NULL;
      }else if( pWalker->eCode==4 ){
        /* A bound parameter in a CREATE statement that originates from
        ** sqlite3_prepare() causes an error */
        pWalker->eCode = 0;
        return WRC_Abort;
      }
      /* no break */ deliberate_fall_through
    default:
      testcase( pExpr->op==TK_SELECT ); /* sqlite3SelectWalkFail() disallows */
      testcase( pExpr->op==TK_EXISTS ); /* sqlite3SelectWalkFail() disallows */
      return WRC_Continue;
  }
}
static int exprIsConst(Parse *pParse, Expr *p, int initFlag){
  Walker w;
  w.eCode = initFlag;
  w.pParse = pParse;
  w.xExprCallback = exprNodeIsConstant;
  w.xSelectCallback = sqlite3SelectWalkFail;
#ifdef SQLITE_DEBUG
  w.xSelectCallback2 = sqlite3SelectWalkAssert2;
#endif
  sqlite3WalkExpr(&w, p);
  return w.eCode;
}

/*
** Walk an expression tree.  Return non-zero if the expression is constant
** or return zero if the expression involves variables or function calls.
**
** For the purposes of this function, a double-quoted string (ex: "abc")
** is considered a variable but a single-quoted string (ex: 'abc') is
** a constant.
**
** The pParse parameter may be NULL.  But if it is NULL, there is no way
** to determine if function calls are constant or not, and hence all
** function calls will be considered to be non-constant.  If pParse is
** not NULL, then a function call might be constant, depending on the
** function and on its parameters.
*/
int sqlite3ExprIsConstant(Parse *pParse, Expr *p){
  return exprIsConst(pParse, p, 1);
}

/*
** Walk an expression tree.  Return non-zero if
**
**   (1) the expression is constant, and
**   (2) the expression does originate in the ON or USING clause
**       of a LEFT JOIN, and
**   (3) the expression does not contain any EP_FixedCol TK_COLUMN
**       operands created by the constant propagation optimization.
**
** When this routine returns true, it indicates that the expression
** can be added to the pParse->pConstExpr list and evaluated once when
** the prepared statement starts up.  See sqlite3ExprCodeRunJustOnce().
*/
static int sqlite3ExprIsConstantNotJoin(Parse *pParse, Expr *p){
  return exprIsConst(pParse, p, 2);
}

/*
** This routine examines sub-SELECT statements as an expression is being
** walked as part of sqlite3ExprIsTableConstant().  Sub-SELECTs are considered
** constant as long as they are uncorrelated - meaning that they do not
** contain any terms from outer contexts.
*/
static int exprSelectWalkTableConstant(Walker *pWalker, Select *pSelect){
  assert( pSelect!=0 );
  assert( pWalker->eCode==3 || pWalker->eCode==0 );
  if( (pSelect->selFlags & SF_Correlated)!=0 ){
    pWalker->eCode = 0;
    return WRC_Abort;
  }
  return WRC_Prune;
}

/*
** Walk an expression tree.  Return non-zero if the expression is constant
** for any single row of the table with cursor iCur.  In other words, the
** expression must not refer to any non-deterministic function nor any
** table other than iCur.
**
** Consider uncorrelated subqueries to be constants if the bAllowSubq
** parameter is true.
*/
static int sqlite3ExprIsTableConstant(Expr *p, int iCur, int bAllowSubq){
  Walker w;
  w.eCode = 3;
  w.pParse = 0;
  w.xExprCallback = exprNodeIsConstant;
  if( bAllowSubq ){
    w.xSelectCallback = exprSelectWalkTableConstant;
  }else{
    w.xSelectCallback = sqlite3SelectWalkFail;
#ifdef SQLITE_DEBUG
    w.xSelectCallback2 = sqlite3SelectWalkAssert2;
#endif
  }
  w.u.iCur = iCur;
  sqlite3WalkExpr(&w, p);
  return w.eCode;
}

/*
** Check pExpr to see if it is an constraint on the single data source
** pSrc = &pSrcList->a[iSrc].  In other words, check to see if pExpr
** constrains pSrc but does not depend on any other tables or data
** sources anywhere else in the query.  Return true (non-zero) if pExpr
** is a constraint on pSrc only.
**
** This is an optimization.  False negatives will perhaps cause slower
** queries, but false positives will yield incorrect answers.  So when in
** doubt, return 0.
**
** To be an single-source constraint, the following must be true:
**
**   (1)  pExpr cannot refer to any table other than pSrc->iCursor.
**
**   (2a) pExpr cannot use subqueries unless the bAllowSubq parameter is
**        true and the subquery is non-correlated
**
**   (2b) pExpr cannot use non-deterministic functions.
**
**   (3)  pSrc cannot be part of the left operand for a RIGHT JOIN.
**        (Is there some way to relax this constraint?)
**
**   (4)  If pSrc is the right operand of a LEFT JOIN, then...
**         (4a)  pExpr must come from an ON clause..
**         (4b)  and specifically the ON clause associated with the LEFT JOIN.
**
**   (5)  If pSrc is the right operand of a LEFT JOIN or the left
**        operand of a RIGHT JOIN, then pExpr must be from the WHERE
**        clause, not an ON clause.
**
**   (6) Either:
**
**       (6a) pExpr does not originate in an ON or USING clause, or
**
**       (6b) The ON or USING clause from which pExpr is derived is
**            not to the left of a RIGHT JOIN (or FULL JOIN).
**
**       Without this restriction, accepting pExpr as a single-table
**       constraint might move the the ON/USING filter expression
**       from the left side of a RIGHT JOIN over to the right side,
**       which leads to incorrect answers.  See also restriction (9)
**       on push-down.
*/
int sqlite3ExprIsSingleTableConstraint(
  Expr *pExpr,                 /* The constraint */
  const SrcList *pSrcList,     /* Complete FROM clause */
  int iSrc,                    /* Which element of pSrcList to use */
  int bAllowSubq               /* Allow non-correlated subqueries */
){
  const SrcItem *pSrc = &pSrcList->a[iSrc];
  if( pSrc->fg.jointype & JT_LTORJ ){
    return 0;  /* rule (3) */
  }
  if( pSrc->fg.jointype & JT_LEFT ){
    if( !ExprHasProperty(pExpr, EP_OuterON) ) return 0;   /* rule (4a) */
    if( pExpr->w.iJoin!=pSrc->iCursor ) return 0;         /* rule (4b) */
  }else{
    if( ExprHasProperty(pExpr, EP_OuterON) ) return 0;    /* rule (5) */
  }
  if( ExprHasProperty(pExpr, EP_OuterON|EP_InnerON)  /* (6a) */
   && (pSrcList->a[0].fg.jointype & JT_LTORJ)!=0     /* Fast pre-test of (6b) */
  ){
    int jj;
    for(jj=0; jj<iSrc; jj++){
      if( pExpr->w.iJoin==pSrcList->a[jj].iCursor ){
        if( (pSrcList->a[jj].fg.jointype & JT_LTORJ)!=0 ){
          return 0;  /* restriction (6) */
        }
        break;
      }
    }
  }
  /* Rules (1), (2a), and (2b) handled by the following: */
  return sqlite3ExprIsTableConstant(pExpr, pSrc->iCursor, bAllowSubq);
}


/*
** sqlite3WalkExpr() callback used by sqlite3ExprIsConstantOrGroupBy().
*/
static int exprNodeIsConstantOrGroupBy(Walker *pWalker, Expr *pExpr){
  ExprList *pGroupBy = pWalker->u.pGroupBy;
  int i;

  /* Check if pExpr is identical to any GROUP BY term. If so, consider
  ** it constant.  */
  for(i=0; i<pGroupBy->nExpr; i++){
    Expr *p = pGroupBy->a[i].pExpr;
    if( sqlite3ExprCompare(0, pExpr, p, -1)<2 ){
      CollSeq *pColl = sqlite3ExprNNCollSeq(pWalker->pParse, p);
      if( sqlite3IsBinary(pColl) ){
        return WRC_Prune;
      }
    }
  }

  /* Check if pExpr is a sub-select. If so, consider it variable. */
  if( ExprUseXSelect(pExpr) ){
    pWalker->eCode = 0;
    return WRC_Abort;
  }

  return exprNodeIsConstant(pWalker, pExpr);
}

/*
** Walk the expression tree passed as the first argument. Return non-zero
** if the expression consists entirely of constants or copies of terms
** in pGroupBy that sort with the BINARY collation sequence.
**
** This routine is used to determine if a term of the HAVING clause can
** be promoted into the WHERE clause.  In order for such a promotion to work,
** the value of the HAVING clause term must be the same for all members of
** a "group".  The requirement that the GROUP BY term must be BINARY
** assumes that no other collating sequence will have a finer-grained
** grouping than binary.  In other words (A=B COLLATE binary) implies
** A=B in every other collating sequence.  The requirement that the
** GROUP BY be BINARY is stricter than necessary.  It would also work
** to promote HAVING clauses that use the same alternative collating
** sequence as the GROUP BY term, but that is much harder to check,
** alternative collating sequences are uncommon, and this is only an
** optimization, so we take the easy way out and simply require the
** GROUP BY to use the BINARY collating sequence.
*/
int sqlite3ExprIsConstantOrGroupBy(Parse *pParse, Expr *p, ExprList *pGroupBy){
  Walker w;
  w.eCode = 1;
  w.xExprCallback = exprNodeIsConstantOrGroupBy;
  w.xSelectCallback = 0;
  w.u.pGroupBy = pGroupBy;
  w.pParse = pParse;
  sqlite3WalkExpr(&w, p);
  return w.eCode;
}

/*
** Walk an expression tree for the DEFAULT field of a column definition
** in a CREATE TABLE statement.  Return non-zero if the expression is
** acceptable for use as a DEFAULT.  That is to say, return non-zero if
** the expression is constant or a function call with constant arguments.
** Return and 0 if there are any variables.
**
** isInit is true when parsing from sqlite_schema.  isInit is false when
** processing a new CREATE TABLE statement.  When isInit is true, parameters
** (such as ? or $abc) in the expression are converted into NULL.  When
** isInit is false, parameters raise an error.  Parameters should not be
** allowed in a CREATE TABLE statement, but some legacy versions of SQLite
** allowed it, so we need to support it when reading sqlite_schema for
** backwards compatibility.
**
** If isInit is true, set EP_FromDDL on every TK_FUNCTION node.
**
** For the purposes of this function, a double-quoted string (ex: "abc")
** is considered a variable but a single-quoted string (ex: 'abc') is
** a constant.
*/
int sqlite3ExprIsConstantOrFunction(Expr *p, u8 isInit){
  assert( isInit==0 || isInit==1 );
  return exprIsConst(0, p, 4+isInit);
}

#ifdef SQLITE_ENABLE_CURSOR_HINTS
/*
** Walk an expression tree.  Return 1 if the expression contains a
** subquery of some kind.  Return 0 if there are no subqueries.
*/
int sqlite3ExprContainsSubquery(Expr *p){
  Walker w;
  w.eCode = 1;
  w.xExprCallback = sqlite3ExprWalkNoop;
  w.xSelectCallback = sqlite3SelectWalkFail;
#ifdef SQLITE_DEBUG
  w.xSelectCallback2 = sqlite3SelectWalkAssert2;
#endif
  sqlite3WalkExpr(&w, p);
  return w.eCode==0;
}
#endif

/*
** If the expression p codes a constant integer that is small enough
** to fit in a 32-bit integer, return 1 and put the value of the integer
** in *pValue.  If the expression is not an integer or if it is too big
** to fit in a signed 32-bit integer, return 0 and leave *pValue unchanged.
**
** If the pParse pointer is provided, then allow the expression p to be
** a parameter (TK_VARIABLE) that is bound to an integer.
** But if pParse is NULL, then p must be a pure integer literal.
*/
int sqlite3ExprIsInteger(const Expr *p, int *pValue, Parse *pParse){
  int rc = 0;
  if( NEVER(p==0) ) return 0;  /* Used to only happen following on OOM */

  /* If an expression is an integer literal that fits in a signed 32-bit
  ** integer, then the EP_IntValue flag will have already been set */
  assert( p->op!=TK_INTEGER || (p->flags & EP_IntValue)!=0
           || sqlite3GetInt32(p->u.zToken, &rc)==0 );

  if( p->flags & EP_IntValue ){
    *pValue = p->u.iValue;
    return 1;
  }
  switch( p->op ){
    case TK_UPLUS: {
      rc = sqlite3ExprIsInteger(p->pLeft, pValue, 0);
      break;
    }
    case TK_UMINUS: {
      int v = 0;
      if( sqlite3ExprIsInteger(p->pLeft, &v, 0) ){
        assert( ((unsigned int)v)!=0x80000000 );
        *pValue = -v;
        rc = 1;
      }
      break;
    }
    case TK_VARIABLE: {
      sqlite3_value *pVal;
      if( pParse==0 ) break;
      if( NEVER(pParse->pVdbe==0) ) break;
      if( (pParse->db->flags & SQLITE_EnableQPSG)!=0 ) break;
      sqlite3VdbeSetVarmask(pParse->pVdbe, p->iColumn);
      pVal = sqlite3VdbeGetBoundValue(pParse->pReprepare, p->iColumn,
                                      SQLITE_AFF_BLOB);
      if( pVal ){
        if( sqlite3_value_type(pVal)==SQLITE_INTEGER ){
          sqlite3_int64 vv = sqlite3_value_int64(pVal);
          if( vv == (vv & 0x7fffffff) ){ /* non-negative numbers only */
            *pValue = (int)vv;
            rc = 1;
          }
        }
        sqlite3ValueFree(pVal);
      }
      break;
    }
    default: break;
  }
  return rc;
}

/*
** Return FALSE if there is no chance that the expression can be NULL.
**
** If the expression might be NULL or if the expression is too complex
** to tell return TRUE. 
**
** This routine is used as an optimization, to skip OP_IsNull opcodes
** when we know that a value cannot be NULL.  Hence, a false positive
** (returning TRUE when in fact the expression can never be NULL) might
** be a small performance hit but is otherwise harmless.  On the other
** hand, a false negative (returning FALSE when the result could be NULL)
** will likely result in an incorrect answer.  So when in doubt, return
** TRUE.
*/
int sqlite3ExprCanBeNull(const Expr *p){
  u8 op;
  assert( p!=0 );
  while( p->op==TK_UPLUS || p->op==TK_UMINUS ){
    p = p->pLeft;
    assert( p!=0 );
  }
  op = p->op;
  if( op==TK_REGISTER ) op = p->op2;
  switch( op ){
    case TK_INTEGER:
    case TK_STRING:
    case TK_FLOAT:
    case TK_BLOB:
      return 0;
    case TK_COLUMN:
      assert( ExprUseYTab(p) );
      return ExprHasProperty(p, EP_CanBeNull)
          || NEVER(p->y.pTab==0) /* Reference to column of index on expr */
#ifdef SQLITE_ALLOW_ROWID_IN_VIEW
          || (p->iColumn==XN_ROWID && IsView(p->y.pTab))
#endif
          || (p->iColumn>=0
              && p->y.pTab->aCol!=0 /* Possible due to prior error */
              && ALWAYS(p->iColumn<p->y.pTab->nCol)
              && p->y.pTab->aCol[p->iColumn].notNull==0);
    default:
      return 1;
  }
}

/*
** Return TRUE if the given expression is a constant which would be
** unchanged by OP_Affinity with the affinity given in the second
** argument.
**
** This routine is used to determine if the OP_Affinity operation
** can be omitted.  When in doubt return FALSE.  A false negative
** is harmless.  A false positive, however, can result in the wrong
** answer.
*/
int sqlite3ExprNeedsNoAffinityChange(const Expr *p, char aff){
  u8 op;
  int unaryMinus = 0;
  if( aff==SQLITE_AFF_BLOB ) return 1;
  while( p->op==TK_UPLUS || p->op==TK_UMINUS ){
    if( p->op==TK_UMINUS ) unaryMinus = 1;
    p = p->pLeft;
  }
  op = p->op;
  if( op==TK_REGISTER ) op = p->op2;
  switch( op ){
    case TK_INTEGER: {
      return aff>=SQLITE_AFF_NUMERIC;
    }
    case TK_FLOAT: {
      return aff>=SQLITE_AFF_NUMERIC;
    }
    case TK_STRING: {
      return !unaryMinus && aff==SQLITE_AFF_TEXT;
    }
    case TK_BLOB: {
      return !unaryMinus;
    }
    case TK_COLUMN: {
      assert( p->iTable>=0 );  /* p cannot be part of a CHECK constraint */
      return aff>=SQLITE_AFF_NUMERIC && p->iColumn<0;
    }
    default: {
      return 0;
    }
  }
}

/*
** Return TRUE if the given string is a row-id column name.
*/
int sqlite3IsRowid(const char *z){
  if( sqlite3StrICmp(z, "_ROWID_")==0 ) return 1;
  if( sqlite3StrICmp(z, "ROWID")==0 ) return 1;
  if( sqlite3StrICmp(z, "OID")==0 ) return 1;
  return 0;
}

/*
** Return a pointer to a buffer containing a usable rowid alias for table
** pTab. An alias is usable if there is not an explicit user-defined column 
** of the same name.
*/
const char *sqlite3RowidAlias(Table *pTab){
  const char *azOpt[] = {"_ROWID_", "ROWID", "OID"};
  int ii;
  assert( VisibleRowid(pTab) );
  for(ii=0; ii<ArraySize(azOpt); ii++){
    if( sqlite3ColumnIndex(pTab, azOpt[ii])<0 ) return azOpt[ii];
  }
  return 0;
}

/*
** pX is the RHS of an IN operator.  If pX is a SELECT statement
** that can be simplified to a direct table access, then return
** a pointer to the SELECT statement.  If pX is not a SELECT statement,
** or if the SELECT statement needs to be materialized into a transient
** table, then return NULL.
*/
#ifndef SQLITE_OMIT_SUBQUERY
static Select *isCandidateForInOpt(const Expr *pX){
  Select *p;
  SrcList *pSrc;
  ExprList *pEList;
  Table *pTab;
  int i;
  if( !ExprUseXSelect(pX) ) return 0;                 /* Not a subquery */
  if( ExprHasProperty(pX, EP_VarSelect)  ) return 0;  /* Correlated subq */
  p = pX->x.pSelect;
  if( p->pPrior ) return 0;              /* Not a compound SELECT */
  if( p->selFlags & (SF_Distinct|SF_Aggregate) ){
    testcase( (p->selFlags & (SF_Distinct|SF_Aggregate))==SF_Distinct );
    testcase( (p->selFlags & (SF_Distinct|SF_Aggregate))==SF_Aggregate );
    return 0; /* No DISTINCT keyword and no aggregate functions */
  }
  assert( p->pGroupBy==0 );              /* Has no GROUP BY clause */
  if( p->pLimit ) return 0;              /* Has no LIMIT clause */
  if( p->pWhere ) return 0;              /* Has no WHERE clause */
  pSrc = p->pSrc;
  assert( pSrc!=0 );
  if( pSrc->nSrc!=1 ) return 0;          /* Single term in FROM clause */
  if( pSrc->a[0].fg.isSubquery) return 0;/* FROM is not a subquery or view */
  pTab = pSrc->a[0].pSTab;
  assert( pTab!=0 );
  assert( !IsView(pTab)  );              /* FROM clause is not a view */
  if( IsVirtual(pTab) ) return 0;        /* FROM clause not a virtual table */
  pEList = p->pEList;
  assert( pEList!=0 );
  /* All SELECT results must be columns. */
  for(i=0; i<pEList->nExpr; i++){
    Expr *pRes = pEList->a[i].pExpr;
    if( pRes->op!=TK_COLUMN ) return 0;
    assert( pRes->iTable==pSrc->a[0].iCursor );  /* Not a correlated subquery */
  }
  return p;
}
#endif /* SQLITE_OMIT_SUBQUERY */

#ifndef SQLITE_OMIT_SUBQUERY
/*
** Generate code that checks the left-most column of index table iCur to see if
** it contains any NULL entries.  Cause the register at regHasNull to be set
** to a non-NULL value if iCur contains no NULLs.  Cause register regHasNull
** to be set to NULL if iCur contains one or more NULL values.
*/
static void sqlite3SetHasNullFlag(Vdbe *v, int iCur, int regHasNull){
  int addr1;
  sqlite3VdbeAddOp2(v, OP_Integer, 0, regHasNull);
  addr1 = sqlite3VdbeAddOp1(v, OP_Rewind, iCur); VdbeCoverage(v);
  sqlite3VdbeAddOp3(v, OP_Column, iCur, 0, regHasNull);
  sqlite3VdbeChangeP5(v, OPFLAG_TYPEOFARG);
  VdbeComment((v, "first_entry_in(%d)", iCur));
  sqlite3VdbeJumpHere(v, addr1);
}
#endif


#ifndef SQLITE_OMIT_SUBQUERY
/*
** The argument is an IN operator with a list (not a subquery) on the
** right-hand side.  Return TRUE if that list is constant.
*/
static int sqlite3InRhsIsConstant(Parse *pParse, Expr *pIn){
  Expr *pLHS;
  int res;
  assert( !ExprHasProperty(pIn, EP_xIsSelect) );
  pLHS = pIn->pLeft;
  pIn->pLeft = 0;
  res = sqlite3ExprIsConstant(pParse, pIn);
  pIn->pLeft = pLHS;
  return res;
}
#endif

/*
** This function is used by the implementation of the IN (...) operator.
** The pX parameter is the expression on the RHS of the IN operator, which
** might be either a list of expressions or a subquery.
**
** The job of this routine is to find or create a b-tree object that can
** be used either to test for membership in the RHS set or to iterate through
** all members of the RHS set, skipping duplicates.
**
** A cursor is opened on the b-tree object that is the RHS of the IN operator
** and the *piTab parameter is set to the index of that cursor.
**
** The returned value of this function indicates the b-tree type, as follows:
**
**   IN_INDEX_ROWID      - The cursor was opened on a database table.
**   IN_INDEX_INDEX_ASC  - The cursor was opened on an ascending index.
**   IN_INDEX_INDEX_DESC - The cursor was opened on a descending index.
**   IN_INDEX_EPH        - The cursor was opened on a specially created and
**                         populated ephemeral table.
**   IN_INDEX_NOOP       - No cursor was allocated.  The IN operator must be
**                         implemented as a sequence of comparisons.
**
** An existing b-tree might be used if the RHS expression pX is a simple
** subquery such as:
**
**     SELECT <column1>, <column2>... FROM <table>
**
** If the RHS of the IN operator is a list or a more complex subquery, then
** an ephemeral table might need to be generated from the RHS and then
** pX->iTable made to point to the ephemeral table instead of an
** existing table.  In this case, the creation and initialization of the
** ephemeral table might be put inside of a subroutine, the EP_Subrtn flag
** will be set on pX and the pX->y.sub fields will be set to show where
** the subroutine is coded.
**
** The inFlags parameter must contain, at a minimum, one of the bits
** IN_INDEX_MEMBERSHIP or IN_INDEX_LOOP but not both.  If inFlags contains
** IN_INDEX_MEMBERSHIP, then the generated table will be used for a fast
** membership test.  When the IN_INDEX_LOOP bit is set, the IN index will
** be used to loop over all values of the RHS of the IN operator.
**
** When IN_INDEX_LOOP is used (and the b-tree will be used to iterate
** through the set members) then the b-tree must not contain duplicates.
** An ephemeral table will be created unless the selected columns are guaranteed
** to be unique - either because it is an INTEGER PRIMARY KEY or due to
** a UNIQUE constraint or index.
**
** When IN_INDEX_MEMBERSHIP is used (and the b-tree will be used
** for fast set membership tests) then an ephemeral table must
** be used unless <columns> is a single INTEGER PRIMARY KEY column or an
** index can be found with the specified <columns> as its left-most.
**
** If the IN_INDEX_NOOP_OK and IN_INDEX_MEMBERSHIP are both set and
** if the RHS of the IN operator is a list (not a subquery) then this
** routine might decide that creating an ephemeral b-tree for membership
** testing is too expensive and return IN_INDEX_NOOP.  In that case, the
** calling routine should implement the IN operator using a sequence
** of Eq or Ne comparison operations.
**
** When the b-tree is being used for membership tests, the calling function
** might need to know whether or not the RHS side of the IN operator
** contains a NULL.  If prRhsHasNull is not a NULL pointer and
** if there is any chance that the (...) might contain a NULL value at
** runtime, then a register is allocated and the register number written
** to *prRhsHasNull. If there is no chance that the (...) contains a
** NULL value, then *prRhsHasNull is left unchanged.
**
** If a register is allocated and its location stored in *prRhsHasNull, then
** the value in that register will be NULL if the b-tree contains one or more
** NULL values, and it will be some non-NULL value if the b-tree contains no
** NULL values.
**
** If the aiMap parameter is not NULL, it must point to an array containing
** one element for each column returned by the SELECT statement on the RHS
** of the IN(...) operator. The i'th entry of the array is populated with the
** offset of the index column that matches the i'th column returned by the
** SELECT. For example, if the expression and selected index are:
**
**   (?,?,?) IN (SELECT a, b, c FROM t1)
**   CREATE INDEX i1 ON t1(b, c, a);
**
** then aiMap[] is populated with {2, 0, 1}.
*/
#ifndef SQLITE_OMIT_SUBQUERY
int sqlite3FindInIndex(
  Parse *pParse,             /* Parsing context */
  Expr *pX,                  /* The IN expression */
  u32 inFlags,               /* IN_INDEX_LOOP, _MEMBERSHIP, and/or _NOOP_OK */
  int *prRhsHasNull,         /* Register holding NULL status.  See notes */
  int *aiMap,                /* Mapping from Index fields to RHS fields */
  int *piTab                 /* OUT: index to use */
){
  Select *p;                            /* SELECT to the right of IN operator */
  int eType = 0;                        /* Type of RHS table. IN_INDEX_* */
  int iTab;                             /* Cursor of the RHS table */
  int mustBeUnique;                     /* True if RHS must be unique */
  Vdbe *v = sqlite3GetVdbe(pParse);     /* Virtual machine being coded */

  assert( pX->op==TK_IN );
  mustBeUnique = (inFlags & IN_INDEX_LOOP)!=0;
  iTab = pParse->nTab++;

  /* If the RHS of this IN(...) operator is a SELECT, and if it matters
  ** whether or not the SELECT result contains NULL values, check whether
  ** or not NULL is actually possible (it may not be, for example, due
  ** to NOT NULL constraints in the schema). If no NULL values are possible,
  ** set prRhsHasNull to 0 before continuing.  */
  if( prRhsHasNull && ExprUseXSelect(pX) ){
    int i;
    ExprList *pEList = pX->x.pSelect->pEList;
    for(i=0; i<pEList->nExpr; i++){
      if( sqlite3ExprCanBeNull(pEList->a[i].pExpr) ) break;
    }
    if( i==pEList->nExpr ){
      prRhsHasNull = 0;
    }
  }

  /* Check to see if an existing table or index can be used to
  ** satisfy the query.  This is preferable to generating a new
  ** ephemeral table.  */
  if( pParse->nErr==0 && (p = isCandidateForInOpt(pX))!=0 ){
    sqlite3 *db = pParse->db;              /* Database connection */
    Table *pTab;                           /* Table <table>. */
    int iDb;                               /* Database idx for pTab */
    ExprList *pEList = p->pEList;
    int nExpr = pEList->nExpr;

    assert( p->pEList!=0 );             /* Because of isCandidateForInOpt(p) */
    assert( p->pEList->a[0].pExpr!=0 ); /* Because of isCandidateForInOpt(p) */
    assert( p->pSrc!=0 );               /* Because of isCandidateForInOpt(p) */
    pTab = p->pSrc->a[0].pSTab;

    /* Code an OP_Transaction and OP_TableLock for <table>. */
    iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
    assert( iDb>=0 && iDb<SQLITE_MAX_DB );
    sqlite3CodeVerifySchema(pParse, iDb);
    sqlite3TableLock(pParse, iDb, pTab->tnum, 0, pTab->zName);

    assert(v);  /* sqlite3GetVdbe() has always been previously called */
    if( nExpr==1 && pEList->a[0].pExpr->iColumn<0 ){
      /* The "x IN (SELECT rowid FROM table)" case */
      int iAddr = sqlite3VdbeAddOp0(v, OP_Once);
      VdbeCoverage(v);

      sqlite3OpenTable(pParse, iTab, iDb, pTab, OP_OpenRead);
      eType = IN_INDEX_ROWID;
      ExplainQueryPlan((pParse, 0,
            "USING ROWID SEARCH ON TABLE %s FOR IN-OPERATOR",pTab->zName));
      sqlite3VdbeJumpHere(v, iAddr);
    }else{
      Index *pIdx;                         /* Iterator variable */
      int affinity_ok = 1;
      int i;

      /* Check that the affinity that will be used to perform each
      ** comparison is the same as the affinity of each column in table
      ** on the RHS of the IN operator.  If it not, it is not possible to
      ** use any index of the RHS table.  */
      for(i=0; i<nExpr && affinity_ok; i++){
        Expr *pLhs = sqlite3VectorFieldSubexpr(pX->pLeft, i);
        int iCol = pEList->a[i].pExpr->iColumn;
        char idxaff = sqlite3TableColumnAffinity(pTab,iCol); /* RHS table */
        char cmpaff = sqlite3CompareAffinity(pLhs, idxaff);
        testcase( cmpaff==SQLITE_AFF_BLOB );
        testcase( cmpaff==SQLITE_AFF_TEXT );
        switch( cmpaff ){
          case SQLITE_AFF_BLOB:
            break;
          case SQLITE_AFF_TEXT:
            /* sqlite3CompareAffinity() only returns TEXT if one side or the
            ** other has no affinity and the other side is TEXT.  Hence,
            ** the only way for cmpaff to be TEXT is for idxaff to be TEXT
            ** and for the term on the LHS of the IN to have no affinity. */
            assert( idxaff==SQLITE_AFF_TEXT );
            break;
          default:
            affinity_ok = sqlite3IsNumericAffinity(idxaff);
        }
      }

      if( affinity_ok ){
        /* Search for an existing index that will work for this IN operator */
        for(pIdx=pTab->pIndex; pIdx && eType==0; pIdx=pIdx->pNext){
          Bitmask colUsed;      /* Columns of the index used */
          Bitmask mCol;         /* Mask for the current column */
          if( pIdx->nColumn<nExpr ) continue;
          if( pIdx->pPartIdxWhere!=0 ) continue;
          /* Maximum nColumn is BMS-2, not BMS-1, so that we can compute
          ** BITMASK(nExpr) without overflowing */
          testcase( pIdx->nColumn==BMS-2 );
          testcase( pIdx->nColumn==BMS-1 );
          if( pIdx->nColumn>=BMS-1 ) continue;
          if( mustBeUnique ){
            if( pIdx->nKeyCol>nExpr
             ||(pIdx->nColumn>nExpr && !IsUniqueIndex(pIdx))
            ){
              continue;  /* This index is not unique over the IN RHS columns */
            }
          }
 
          colUsed = 0;   /* Columns of index used so far */
          for(i=0; i<nExpr; i++){
            Expr *pLhs = sqlite3VectorFieldSubexpr(pX->pLeft, i);
            Expr *pRhs = pEList->a[i].pExpr;
            CollSeq *pReq = sqlite3BinaryCompareCollSeq(pParse, pLhs, pRhs);
            int j;
 
            for(j=0; j<nExpr; j++){
              if( pIdx->aiColumn[j]!=pRhs->iColumn ) continue;
              assert( pIdx->azColl[j] );
              if( pReq!=0 && sqlite3StrICmp(pReq->zName, pIdx->azColl[j])!=0 ){
                continue;
              }
              break;
            }
            if( j==nExpr ) break;
            mCol = MASKBIT(j);
            if( mCol & colUsed ) break; /* Each column used only once */
            colUsed |= mCol;
            if( aiMap ) aiMap[i] = j;
          }
 
          assert( nExpr>0 && nExpr<BMS );
          assert( i==nExpr || colUsed!=(MASKBIT(nExpr)-1) );
          if( colUsed==(MASKBIT(nExpr)-1) ){
            /* If we reach this point, that means the index pIdx is usable */
            int iAddr = sqlite3VdbeAddOp0(v, OP_Once); VdbeCoverage(v);
            ExplainQueryPlan((pParse, 0,
                              "USING INDEX %s FOR IN-OPERATOR",pIdx->zName));
            sqlite3VdbeAddOp3(v, OP_OpenRead, iTab, pIdx->tnum, iDb);
            sqlite3VdbeSetP4KeyInfo(pParse, pIdx);
            VdbeComment((v, "%s", pIdx->zName));
            assert( IN_INDEX_INDEX_DESC == IN_INDEX_INDEX_ASC+1 );
            eType = IN_INDEX_INDEX_ASC + pIdx->aSortOrder[0];
 
            if( prRhsHasNull ){
#ifdef SQLITE_ENABLE_COLUMN_USED_MASK
              i64 mask = (1<<nExpr)-1;
              sqlite3VdbeAddOp4Dup8(v, OP_ColumnsUsed,
                  iTab, 0, 0, (u8*)&mask, P4_INT64);
#endif
              *prRhsHasNull = ++pParse->nMem;
              if( nExpr==1 ){
                sqlite3SetHasNullFlag(v, iTab, *prRhsHasNull);
              }
            }
            sqlite3VdbeJumpHere(v, iAddr);
          }
        } /* End loop over indexes */
      } /* End if( affinity_ok ) */
    } /* End if not an rowid index */
  } /* End attempt to optimize using an index */

  /* If no preexisting index is available for the IN clause
  ** and IN_INDEX_NOOP is an allowed reply
  ** and the RHS of the IN operator is a list, not a subquery
  ** and the RHS is not constant or has two or fewer terms,
  ** then it is not worth creating an ephemeral table to evaluate
  ** the IN operator so return IN_INDEX_NOOP.
  */
  if( eType==0
   && (inFlags & IN_INDEX_NOOP_OK)
   && ExprUseXList(pX)
   && (!sqlite3InRhsIsConstant(pParse,pX) || pX->x.pList->nExpr<=2)
  ){
    pParse->nTab--;  /* Back out the allocation of the unused cursor */
    iTab = -1;       /* Cursor is not allocated */
    eType = IN_INDEX_NOOP;
  }

  if( eType==0 ){
    /* Could not find an existing table or index to use as the RHS b-tree.
    ** We will have to generate an ephemeral table to do the job.
    */
    u32 savedNQueryLoop = pParse->nQueryLoop;
    int rMayHaveNull = 0;
    int bloomOk = (inFlags & IN_INDEX_MEMBERSHIP)!=0;
    eType = IN_INDEX_EPH;
    if( inFlags & IN_INDEX_LOOP ){
      pParse->nQueryLoop = 0;
    }else if( prRhsHasNull ){
      *prRhsHasNull = rMayHaveNull = ++pParse->nMem;
    }
    assert( pX->op==TK_IN );
    if( !bloomOk
     && ExprUseXSelect(pX)
     && (pX->x.pSelect->selFlags & SF_ClonedRhsIn)!=0
    ){
      bloomOk = 1;
    }
    sqlite3CodeRhsOfIN(pParse, pX, iTab, bloomOk);
    if( rMayHaveNull ){
      sqlite3SetHasNullFlag(v, iTab, rMayHaveNull);
    }
    pParse->nQueryLoop = savedNQueryLoop;
  }

  if( aiMap && eType!=IN_INDEX_INDEX_ASC && eType!=IN_INDEX_INDEX_DESC ){
    int i, n;
    n = sqlite3ExprVectorSize(pX->pLeft);
    for(i=0; i<n; i++) aiMap[i] = i;
  }
  *piTab = iTab;
  return eType;
}
#endif

#ifndef SQLITE_OMIT_SUBQUERY
/*
** Argument pExpr is an (?, ?...) IN(...) expression. This
** function allocates and returns a nul-terminated string containing
** the affinities to be used for each column of the comparison.
**
** It is the responsibility of the caller to ensure that the returned
** string is eventually freed using sqlite3DbFree().
*/
static char *exprINAffinity(Parse *pParse, const Expr *pExpr){
  Expr *pLeft = pExpr->pLeft;
  int nVal = sqlite3ExprVectorSize(pLeft);
  Select *pSelect = ExprUseXSelect(pExpr) ? pExpr->x.pSelect : 0;
  char *zRet;

  assert( pExpr->op==TK_IN );
  zRet = sqlite3DbMallocRaw(pParse->db, 1+(i64)nVal);
  if( zRet ){
    int i;
    for(i=0; i<nVal; i++){
      Expr *pA = sqlite3VectorFieldSubexpr(pLeft, i);
      char a = sqlite3ExprAffinity(pA);
      if( pSelect ){
        zRet[i] = sqlite3CompareAffinity(pSelect->pEList->a[i].pExpr, a);
      }else{
        zRet[i] = a;
      }
    }
    zRet[nVal] = '\0';
  }
  return zRet;
}
#endif

#ifndef SQLITE_OMIT_SUBQUERY
/*
** Load the Parse object passed as the first argument with an error
** message of the form:
**
**   "sub-select returns N columns - expected M"
*/  
void sqlite3SubselectError(Parse *pParse, int nActual, int nExpect){
  if( pParse->nErr==0 ){
    const char *zFmt = "sub-select returns %d columns - expected %d";
    sqlite3ErrorMsg(pParse, zFmt, nActual, nExpect);
  }
}
#endif

/*
** Expression pExpr is a vector that has been used in a context where
** it is not permitted. If pExpr is a sub-select vector, this routine
** loads the Parse object with a message of the form:
**
**   "sub-select returns N columns - expected 1"
**
** Or, if it is a regular scalar vector:
**
**   "row value misused"
*/  
void sqlite3VectorErrorMsg(Parse *pParse, Expr *pExpr){
#ifndef SQLITE_OMIT_SUBQUERY
  if( ExprUseXSelect(pExpr) ){
    sqlite3SubselectError(pParse, pExpr->x.pSelect->pEList->nExpr, 1);
  }else
#endif
  {
    sqlite3ErrorMsg(pParse, "row value misused");
  }
}

#ifndef SQLITE_OMIT_SUBQUERY
/*
** Scan all previously generated bytecode looking for an OP_BeginSubrtn
** that is compatible with pExpr.  If found, add the y.sub values
** to pExpr and return true.  If not found, return false.
*/
static int findCompatibleInRhsSubrtn(
  Parse *pParse,          /* Parsing context */
  Expr *pExpr,            /* IN operator with RHS that we want to reuse */
  SubrtnSig *pNewSig      /* Signature for the IN operator */
){
  VdbeOp *pOp, *pEnd;
  SubrtnSig *pSig;
  Vdbe *v;

  if( pNewSig==0 ) return 0;
  if( (pParse->mSubrtnSig & (1<<(pNewSig->selId&7)))==0 ) return 0;
  assert( pExpr->op==TK_IN );
  assert( !ExprUseYSub(pExpr) );
  assert( ExprUseXSelect(pExpr) );
  assert( pExpr->x.pSelect!=0 );
  assert( (pExpr->x.pSelect->selFlags & SF_All)==0 );
  v = pParse->pVdbe;
  assert( v!=0 );
  pOp = sqlite3VdbeGetOp(v, 1);
  pEnd = sqlite3VdbeGetLastOp(v);
  for(; pOp<pEnd; pOp++){
    if( pOp->p4type!=P4_SUBRTNSIG ) continue;
    assert( pOp->opcode==OP_BeginSubrtn );
    pSig = pOp->p4.pSubrtnSig;
    assert( pSig!=0 );
    if( !pSig->bComplete ) continue;
    if( pNewSig->selId!=pSig->selId ) continue;
    if( strcmp(pNewSig->zAff,pSig->zAff)!=0 ) continue;
    pExpr->y.sub.iAddr = pSig->iAddr;
    pExpr->y.sub.regReturn = pSig->regReturn;
    pExpr->iTable = pSig->iTable;
    ExprSetProperty(pExpr, EP_Subrtn);
    return 1;
  }
  return 0;
}
#endif /* SQLITE_OMIT_SUBQUERY */

#ifndef SQLITE_OMIT_SUBQUERY
/*
** Generate code that will construct an ephemeral table containing all terms
** in the RHS of an IN operator.  The IN operator can be in either of two
** forms:
**
**     x IN (4,5,11)              -- IN operator with list on right-hand side
**     x IN (SELECT a FROM b)     -- IN operator with subquery on the right
**
** The pExpr parameter is the IN operator.  The cursor number for the
** constructed ephemeral table is returned.  The first time the ephemeral
** table is computed, the cursor number is also stored in pExpr->iTable,
** however the cursor number returned might not be the same, as it might
** have been duplicated using OP_OpenDup.
**
** If the LHS expression ("x" in the examples) is a column value, or
** the SELECT statement returns a column value, then the affinity of that
** column is used to build the index keys. If both 'x' and the
** SELECT... statement are columns, then numeric affinity is used
** if either column has NUMERIC or INTEGER affinity. If neither
** 'x' nor the SELECT... statement are columns, then numeric affinity
** is used.
*/
void sqlite3CodeRhsOfIN(
  Parse *pParse,          /* Parsing context */
  Expr *pExpr,            /* The IN operator */
  int iTab,               /* Use this cursor number */
  int allowBloom          /* True to allow the use of a Bloom filter */
){
  int addrOnce = 0;           /* Address of the OP_Once instruction at top */
  int addr;                   /* Address of OP_OpenEphemeral instruction */
  Expr *pLeft;                /* the LHS of the IN operator */
  KeyInfo *pKeyInfo = 0;      /* Key information */
  int nVal;                   /* Size of vector pLeft */
  Vdbe *v;                    /* The prepared statement under construction */
  SubrtnSig *pSig = 0;        /* Signature for this subroutine */

  v = pParse->pVdbe;
  assert( v!=0 );

  /* The evaluation of the IN must be repeated every time it
  ** is encountered if any of the following is true:
  **
  **    *  The right-hand side is a correlated subquery
  **    *  The right-hand side is an expression list containing variables
  **    *  We are inside a trigger
  **
  ** If all of the above are false, then we can compute the RHS just once
  ** and reuse it many names.
  */
  if( !ExprHasProperty(pExpr, EP_VarSelect) && pParse->iSelfTab==0 ){
    /* Reuse of the RHS is allowed
    **
    ** Compute a signature for the RHS of the IN operator to facility
    ** finding and reusing prior instances of the same IN operator.
    */
    assert( !ExprUseXSelect(pExpr) || pExpr->x.pSelect!=0 );
    if( ExprUseXSelect(pExpr) && (pExpr->x.pSelect->selFlags & SF_All)==0 ){
      pSig = sqlite3DbMallocRawNN(pParse->db, sizeof(pSig[0]));
      if( pSig ){
        pSig->selId = pExpr->x.pSelect->selId;
        pSig->zAff = exprINAffinity(pParse, pExpr);
      }
    }

    /* Check to see if there is a prior materialization of the RHS of
    ** this IN operator.  If there is, then make use of that prior
    ** materialization rather than recomputing it.
    */
    if( ExprHasProperty(pExpr, EP_Subrtn) 
     || findCompatibleInRhsSubrtn(pParse, pExpr, pSig)
    ){
      addrOnce = sqlite3VdbeAddOp0(v, OP_Once); VdbeCoverage(v);
      if( ExprUseXSelect(pExpr) ){
        ExplainQueryPlan((pParse, 0, "REUSE LIST SUBQUERY %d",
              pExpr->x.pSelect->selId));
      }
      assert( ExprUseYSub(pExpr) );
      sqlite3VdbeAddOp2(v, OP_Gosub, pExpr->y.sub.regReturn,
                        pExpr->y.sub.iAddr);
      assert( iTab!=pExpr->iTable );
      sqlite3VdbeAddOp2(v, OP_OpenDup, iTab, pExpr->iTable);
      sqlite3VdbeJumpHere(v, addrOnce);
      if( pSig ){
        sqlite3DbFree(pParse->db, pSig->zAff);
        sqlite3DbFree(pParse->db, pSig);
      }
      return;
    }

    /* Begin coding the subroutine */
    assert( !ExprUseYWin(pExpr) );
    ExprSetProperty(pExpr, EP_Subrtn);
    assert( !ExprHasProperty(pExpr, EP_TokenOnly|EP_Reduced) );
    pExpr->y.sub.regReturn = ++pParse->nMem;
    pExpr->y.sub.iAddr =
      sqlite3VdbeAddOp2(v, OP_BeginSubrtn, 0, pExpr->y.sub.regReturn) + 1;
    if( pSig ){
      pSig->bComplete = 0;
      pSig->iAddr = pExpr->y.sub.iAddr;
      pSig->regReturn = pExpr->y.sub.regReturn;
      pSig->iTable = iTab;
      pParse->mSubrtnSig = 1 << (pSig->selId&7);
      sqlite3VdbeChangeP4(v, -1, (const char*)pSig, P4_SUBRTNSIG);
    }
    addrOnce = sqlite3VdbeAddOp0(v, OP_Once); VdbeCoverage(v);
  }

  /* Check to see if this is a vector IN operator */
  pLeft = pExpr->pLeft;
  nVal = sqlite3ExprVectorSize(pLeft);

  /* Construct the ephemeral table that will contain the content of
  ** RHS of the IN operator.
  */
  pExpr->iTable = iTab;
  addr = sqlite3VdbeAddOp2(v, OP_OpenEphemeral, pExpr->iTable, nVal);
#ifdef SQLITE_ENABLE_EXPLAIN_COMMENTS
  if( ExprUseXSelect(pExpr) ){
    VdbeComment((v, "Result of SELECT %u", pExpr->x.pSelect->selId));
  }else{
    VdbeComment((v, "RHS of IN operator"));
  }
#endif
  pKeyInfo = sqlite3KeyInfoAlloc(pParse->db, nVal, 1);

  if( ExprUseXSelect(pExpr) ){
    /* Case 1:     expr IN (SELECT ...)
    **
    ** Generate code to write the results of the select into the temporary
    ** table allocated and opened above.
    */
    Select *pSelect = pExpr->x.pSelect;
    ExprList *pEList = pSelect->pEList;

    ExplainQueryPlan((pParse, 1, "%sLIST SUBQUERY %d",
        addrOnce?"":"CORRELATED ", pSelect->selId
    ));
    /* If the LHS and RHS of the IN operator do not match, that
    ** error will have been caught long before we reach this point. */
    if( ALWAYS(pEList->nExpr==nVal) ){
      Select *pCopy;
      SelectDest dest;
      int i;
      int rc;
      int addrBloom = 0;
      sqlite3SelectDestInit(&dest, SRT_Set, iTab);
      dest.zAffSdst = exprINAffinity(pParse, pExpr);
      pSelect->iLimit = 0;
      if( addrOnce
       && allowBloom
       && OptimizationEnabled(pParse->db, SQLITE_BloomFilter)
      ){
        int regBloom = ++pParse->nMem;
        addrBloom = sqlite3VdbeAddOp2(v, OP_Blob, 10000, regBloom);
        VdbeComment((v, "Bloom filter"));
        dest.iSDParm2 = regBloom;
      }
      testcase( pSelect->selFlags & SF_Distinct );
      testcase( pKeyInfo==0 ); /* Caused by OOM in sqlite3KeyInfoAlloc() */
      pCopy = sqlite3SelectDup(pParse->db, pSelect, 0);
      rc = pParse->db->mallocFailed ? 1 :sqlite3Select(pParse, pCopy, &dest);
      sqlite3SelectDelete(pParse->db, pCopy);
      sqlite3DbFree(pParse->db, dest.zAffSdst);
      if( addrBloom ){
        /* Remember that location of the Bloom filter in the P3 operand
        ** of the OP_Once that began this subroutine. tag-202407032019 */
        sqlite3VdbeGetOp(v, addrOnce)->p3 = dest.iSDParm2;
        if( dest.iSDParm2==0 ){
          /* If the Bloom filter won't actually be used, keep it small */
          sqlite3VdbeGetOp(v, addrBloom)->p1 = 10;
        }
      }
      if( rc ){
        sqlite3KeyInfoUnref(pKeyInfo);
        return;
      }
      assert( pKeyInfo!=0 ); /* OOM will cause exit after sqlite3Select() */
      assert( pEList!=0 );
      assert( pEList->nExpr>0 );
      assert( sqlite3KeyInfoIsWriteable(pKeyInfo) );
      for(i=0; i<nVal; i++){
        Expr *p = sqlite3VectorFieldSubexpr(pLeft, i);
        pKeyInfo->aColl[i] = sqlite3BinaryCompareCollSeq(
            pParse, p, pEList->a[i].pExpr
        );
      }
    }
  }else if( ALWAYS(pExpr->x.pList!=0) ){
    /* Case 2:     expr IN (exprlist)
    **
    ** For each expression, build an index key from the evaluation and
    ** store it in the temporary table. If <expr> is a column, then use
    ** that columns affinity when building index keys. If <expr> is not
    ** a column, use numeric affinity.
    */
    char affinity;            /* Affinity of the LHS of the IN */
    int i;
    ExprList *pList = pExpr->x.pList;
    struct ExprList_item *pItem;
    int r1, r2;
    affinity = sqlite3ExprAffinity(pLeft);
    if( affinity<=SQLITE_AFF_NONE ){
      affinity = SQLITE_AFF_BLOB;
    }else if( affinity==SQLITE_AFF_REAL ){
      affinity = SQLITE_AFF_NUMERIC;
    }
    if( pKeyInfo ){
      assert( sqlite3KeyInfoIsWriteable(pKeyInfo) );
      pKeyInfo->aColl[0] = sqlite3ExprCollSeq(pParse, pExpr->pLeft);
    }

    /* Loop through each expression in <exprlist>. */
    r1 = sqlite3GetTempReg(pParse);
    r2 = sqlite3GetTempReg(pParse);
    for(i=pList->nExpr, pItem=pList->a; i>0; i--, pItem++){
      Expr *pE2 = pItem->pExpr;

      /* If the expression is not constant then we will need to
      ** disable the test that was generated above that makes sure
      ** this code only executes once.  Because for a non-constant
      ** expression we need to rerun this code each time.
      */
      if( addrOnce && !sqlite3ExprIsConstant(pParse, pE2) ){
        sqlite3VdbeChangeToNoop(v, addrOnce-1);
        sqlite3VdbeChangeToNoop(v, addrOnce);
        ExprClearProperty(pExpr, EP_Subrtn);
        addrOnce = 0;
      }

      /* Evaluate the expression and insert it into the temp table */
      sqlite3ExprCode(pParse, pE2, r1);
      sqlite3VdbeAddOp4(v, OP_MakeRecord, r1, 1, r2, &affinity, 1);
      sqlite3VdbeAddOp4Int(v, OP_IdxInsert, iTab, r2, r1, 1);
    }
    sqlite3ReleaseTempReg(pParse, r1);
    sqlite3ReleaseTempReg(pParse, r2);
  }
  if( pSig ) pSig->bComplete = 1;
  if( pKeyInfo ){
    sqlite3VdbeChangeP4(v, addr, (void *)pKeyInfo, P4_KEYINFO);
  }
  if( addrOnce ){
    sqlite3VdbeAddOp1(v, OP_NullRow, iTab);
    sqlite3VdbeJumpHere(v, addrOnce);
    /* Subroutine return */
    assert( ExprUseYSub(pExpr) );
    assert( sqlite3VdbeGetOp(v,pExpr->y.sub.iAddr-1)->opcode==OP_BeginSubrtn
            || pParse->nErr );
    sqlite3VdbeAddOp3(v, OP_Return, pExpr->y.sub.regReturn,
                      pExpr->y.sub.iAddr, 1);
    VdbeCoverage(v);
    sqlite3ClearTempRegCache(pParse);
  }
}
#endif /* SQLITE_OMIT_SUBQUERY */

/*
** Generate code for scalar subqueries used as a subquery expression
** or EXISTS operator:
**
**     (SELECT a FROM b)          -- subquery
**     EXISTS (SELECT a FROM b)   -- EXISTS subquery
**
** The pExpr parameter is the SELECT or EXISTS operator to be coded.
**
** Return the register that holds the result.  For a multi-column SELECT,
** the result is stored in a contiguous array of registers and the
** return value is the register of the left-most result column.
** Return 0 if an error occurs.
*/
#ifndef SQLITE_OMIT_SUBQUERY
int sqlite3CodeSubselect(Parse *pParse, Expr *pExpr){
  int addrOnce = 0;           /* Address of OP_Once at top of subroutine */
  int rReg = 0;               /* Register storing resulting */
  Select *pSel;               /* SELECT statement to encode */
  SelectDest dest;            /* How to deal with SELECT result */
  int nReg;                   /* Registers to allocate */
  Expr *pLimit;               /* New limit expression */
#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
  int addrExplain;            /* Address of OP_Explain instruction */
#endif

  Vdbe *v = pParse->pVdbe;
  assert( v!=0 );
  if( pParse->nErr ) return 0;
  testcase( pExpr->op==TK_EXISTS );
  testcase( pExpr->op==TK_SELECT );
  assert( pExpr->op==TK_EXISTS || pExpr->op==TK_SELECT );
  assert( ExprUseXSelect(pExpr) );
  pSel = pExpr->x.pSelect;

  /* If this routine has already been coded, then invoke it as a
  ** subroutine. */
  if( ExprHasProperty(pExpr, EP_Subrtn) ){
    ExplainQueryPlan((pParse, 0, "REUSE SUBQUERY %d", pSel->selId));
    assert( ExprUseYSub(pExpr) );
    sqlite3VdbeAddOp2(v, OP_Gosub, pExpr->y.sub.regReturn,
                      pExpr->y.sub.iAddr);
    return pExpr->iTable;
  }

  /* Begin coding the subroutine */
  assert( !ExprUseYWin(pExpr) );
  assert( !ExprHasProperty(pExpr, EP_Reduced|EP_TokenOnly) );
  ExprSetProperty(pExpr, EP_Subrtn);
  pExpr->y.sub.regReturn = ++pParse->nMem;
  pExpr->y.sub.iAddr =
    sqlite3VdbeAddOp2(v, OP_BeginSubrtn, 0, pExpr->y.sub.regReturn) + 1;

  /* The evaluation of the EXISTS/SELECT must be repeated every time it
  ** is encountered if any of the following is true:
  **
  **    *  The right-hand side is a correlated subquery
  **    *  The right-hand side is an expression list containing variables
  **    *  We are inside a trigger
  **
  ** If all of the above are false, then we can run this code just once
  ** save the results, and reuse the same result on subsequent invocations.
  */
  if( !ExprHasProperty(pExpr, EP_VarSelect) ){
    addrOnce = sqlite3VdbeAddOp0(v, OP_Once); VdbeCoverage(v);
  }
 
  /* For a SELECT, generate code to put the values for all columns of
  ** the first row into an array of registers and return the index of
  ** the first register.
  **
  ** If this is an EXISTS, write an integer 0 (not exists) or 1 (exists)
  ** into a register and return that register number.
  **
  ** In both cases, the query is augmented with "LIMIT 1".  Any
  ** preexisting limit is discarded in place of the new LIMIT 1.
  */
  ExplainQueryPlan2(addrExplain, (pParse, 1, "%sSCALAR SUBQUERY %d",
        addrOnce?"":"CORRELATED ", pSel->selId));
  sqlite3VdbeScanStatusCounters(v, addrExplain, addrExplain, -1);
  nReg = pExpr->op==TK_SELECT ? pSel->pEList->nExpr : 1;
  sqlite3SelectDestInit(&dest, 0, pParse->nMem+1);
  pParse->nMem += nReg;
  if( pExpr->op==TK_SELECT ){
    dest.eDest = SRT_Mem;
    if( (pSel->selFlags&SF_Distinct) && pSel->pLimit && pSel->pLimit->pRight ){
      /* If there is both a DISTINCT and an OFFSET clause, then allocate
      ** a separate dest.iSdst array for sqlite3Select() and other
      ** routines to populate. In this case results will be copied over
      ** into the dest.iSDParm array only after OFFSET processing. This
      ** ensures that in the case where OFFSET excludes all rows, the
      ** dest.iSDParm array is not left populated with the contents of the
      ** last row visited - it should be all NULLs if all rows were
      ** excluded by OFFSET.  */ 
      dest.iSdst = pParse->nMem+1;
      pParse->nMem += nReg;
    }else{
      dest.iSdst = dest.iSDParm;
    }
    dest.nSdst = nReg;
    sqlite3VdbeAddOp3(v, OP_Null, 0, dest.iSDParm, pParse->nMem);
    VdbeComment((v, "Init subquery result"));
  }else{
    dest.eDest = SRT_Exists;
    sqlite3VdbeAddOp2(v, OP_Integer, 0, dest.iSDParm);
    VdbeComment((v, "Init EXISTS result"));
  }
  if( pSel->pLimit ){
    /* The subquery already has a limit.  If the pre-existing limit X is 
    ** not already integer value 1 or 0, then make the new limit X<>0 so that
    ** the new limit is either 1 or 0 */
    Expr *pLeft = pSel->pLimit->pLeft;
    if( ExprHasProperty(pLeft, EP_IntValue)==0
     || (pLeft->u.iValue!=1 && pLeft->u.iValue!=0)
    ){
      sqlite3 *db = pParse->db;
      pLimit = sqlite3ExprInt32(db, 0);
      if( pLimit ){
        pLimit->affExpr = SQLITE_AFF_NUMERIC;
        pLimit = sqlite3PExpr(pParse, TK_NE,
            sqlite3ExprDup(db, pLeft, 0), pLimit);
      }
      sqlite3ExprDeferredDelete(pParse, pLeft);
      pSel->pLimit->pLeft = pLimit;
    }
  }else{
    /* If there is no pre-existing limit add a limit of 1 */
    pLimit = sqlite3ExprInt32(pParse->db, 1);
    pSel->pLimit = sqlite3PExpr(pParse, TK_LIMIT, pLimit, 0);
  }
  pSel->iLimit = 0;
  if( sqlite3Select(pParse, pSel, &dest) ){
    pExpr->op2 = pExpr->op;
    pExpr->op = TK_ERROR;
    return 0;
  }
  pExpr->iTable = rReg = dest.iSDParm;
  ExprSetVVAProperty(pExpr, EP_NoReduce);
  if( addrOnce ){
    sqlite3VdbeJumpHere(v, addrOnce);
  }
  sqlite3VdbeScanStatusRange(v, addrExplain, addrExplain, -1);

  /* Subroutine return */
  assert( ExprUseYSub(pExpr) );
  assert( sqlite3VdbeGetOp(v,pExpr->y.sub.iAddr-1)->opcode==OP_BeginSubrtn
          || pParse->nErr );
  sqlite3VdbeAddOp3(v, OP_Return, pExpr->y.sub.regReturn,
                    pExpr->y.sub.iAddr, 1);
  VdbeCoverage(v);
  sqlite3ClearTempRegCache(pParse);
  return rReg;
}
#endif /* SQLITE_OMIT_SUBQUERY */

#ifndef SQLITE_OMIT_SUBQUERY
/*
** Expr pIn is an IN(...) expression. This function checks that the
** sub-select on the RHS of the IN() operator has the same number of
** columns as the vector on the LHS. Or, if the RHS of the IN() is not
** a sub-query, that the LHS is a vector of size 1.
*/
int sqlite3ExprCheckIN(Parse *pParse, Expr *pIn){
  int nVector = sqlite3ExprVectorSize(pIn->pLeft);
  if( ExprUseXSelect(pIn) && !pParse->db->mallocFailed ){
    if( nVector!=pIn->x.pSelect->pEList->nExpr ){
      sqlite3SubselectError(pParse, pIn->x.pSelect->pEList->nExpr, nVector);
      return 1;
    }
  }else if( nVector!=1 ){
    sqlite3VectorErrorMsg(pParse, pIn->pLeft);
    return 1;
  }
  return 0;
}
#endif

#ifndef SQLITE_OMIT_SUBQUERY
/*
** Generate code for an IN expression.
**
**      x IN (SELECT ...)
**      x IN (value, value, ...)
**
** The left-hand side (LHS) is a scalar or vector expression.  The
** right-hand side (RHS) is an array of zero or more scalar values, or a
** subquery.  If the RHS is a subquery, the number of result columns must
** match the number of columns in the vector on the LHS.  If the RHS is
** a list of values, the LHS must be a scalar.
**
** The IN operator is true if the LHS value is contained within the RHS.
** The result is false if the LHS is definitely not in the RHS.  The
** result is NULL if the presence of the LHS in the RHS cannot be
** determined due to NULLs.
**
** This routine generates code that jumps to destIfFalse if the LHS is not
** contained within the RHS.  If due to NULLs we cannot determine if the LHS
** is contained in the RHS then jump to destIfNull.  If the LHS is contained
** within the RHS then fall through.
**
** See the separate in-operator.md documentation file in the canonical
** SQLite source tree for additional information.
*/
static void sqlite3ExprCodeIN(
  Parse *pParse,        /* Parsing and code generating context */
  Expr *pExpr,          /* The IN expression */
  int destIfFalse,      /* Jump here if LHS is not contained in the RHS */
  int destIfNull        /* Jump here if the results are unknown due to NULLs */
){
  int rRhsHasNull = 0;  /* Register that is true if RHS contains NULL values */
  int eType;            /* Type of the RHS */
  int rLhs;             /* Register(s) holding the LHS values */
  Vdbe *v;              /* Statement under construction */
  int *aiMap = 0;       /* Map from vector field to index column */
  char *zAff = 0;       /* Affinity string for comparisons */
  int nVector;          /* Size of vectors for this IN operator */
  int iDummy;           /* Dummy parameter to exprCodeVector() */
  Expr *pLeft;          /* The LHS of the IN operator */
  int i;                /* loop counter */
  int destStep2;        /* Where to jump when NULLs seen in step 2 */
  int destStep6 = 0;    /* Start of code for Step 6 */
  int addrTruthOp;      /* Address of opcode that determines the IN is true */
  int destNotNull;      /* Jump here if a comparison is not true in step 6 */
  int addrTop;          /* Top of the step-6 loop */
  int iTab = 0;         /* Index to use */
  u8 okConstFactor = pParse->okConstFactor;

  assert( !ExprHasVVAProperty(pExpr,EP_Immutable) );
  pLeft = pExpr->pLeft;
  if( sqlite3ExprCheckIN(pParse, pExpr) ) return;
  zAff = exprINAffinity(pParse, pExpr);
  nVector = sqlite3ExprVectorSize(pExpr->pLeft);
  aiMap = (int*)sqlite3DbMallocZero(pParse->db, nVector*sizeof(int));
  if( pParse->db->mallocFailed ) goto sqlite3ExprCodeIN_oom_error;

  /* Attempt to compute the RHS. After this step, if anything other than
  ** IN_INDEX_NOOP is returned, the table opened with cursor iTab
  ** contains the values that make up the RHS. If IN_INDEX_NOOP is returned,
  ** the RHS has not yet been coded.  */
  v = pParse->pVdbe;
  assert( v!=0 );       /* OOM detected prior to this routine */
  VdbeNoopComment((v, "begin IN expr"));
  eType = sqlite3FindInIndex(pParse, pExpr,
                             IN_INDEX_MEMBERSHIP | IN_INDEX_NOOP_OK,
                             destIfFalse==destIfNull ? 0 : &rRhsHasNull,
                             aiMap, &iTab);

  assert( pParse->nErr || nVector==1 || eType==IN_INDEX_EPH
       || eType==IN_INDEX_INDEX_ASC || eType==IN_INDEX_INDEX_DESC
  );
#ifdef SQLITE_DEBUG
  /* Confirm that aiMap[] contains nVector integer values between 0 and
  ** nVector-1. */
  for(i=0; i<nVector; i++){
    int j, cnt;
    for(cnt=j=0; j<nVector; j++) if( aiMap[j]==i ) cnt++;
    assert( cnt==1 );
  }
#endif

  /* Code the LHS, the <expr> from "<expr> IN (...)". If the LHS is a
  ** vector, then it is stored in an array of nVector registers starting
  ** at r1.
  **
  ** sqlite3FindInIndex() might have reordered the fields of the LHS vector
  ** so that the fields are in the same order as an existing index.   The
  ** aiMap[] array contains a mapping from the original LHS field order to
  ** the field order that matches the RHS index.
  **
  ** Avoid factoring the LHS of the IN(...) expression out of the loop,
  ** even if it is constant, as OP_Affinity may be used on the register
  ** by code generated below.  */
  assert( pParse->okConstFactor==okConstFactor );
  pParse->okConstFactor = 0;
  rLhs = exprCodeVector(pParse, pLeft, &iDummy);
  pParse->okConstFactor = okConstFactor;

  /* If sqlite3FindInIndex() did not find or create an index that is
  ** suitable for evaluating the IN operator, then evaluate using a
  ** sequence of comparisons.
  **
  ** This is step (1) in the in-operator.md optimized algorithm.
  */
  if( eType==IN_INDEX_NOOP ){
    ExprList *pList;
    CollSeq *pColl;
    int labelOk = sqlite3VdbeMakeLabel(pParse);
    int r2, regToFree;
    int regCkNull = 0;
    int ii;
    assert( nVector==1 );
    assert( ExprUseXList(pExpr) );
    pList = pExpr->x.pList;
    pColl = sqlite3ExprCollSeq(pParse, pExpr->pLeft);
    if( destIfNull!=destIfFalse ){
      regCkNull = sqlite3GetTempReg(pParse);
      sqlite3VdbeAddOp3(v, OP_BitAnd, rLhs, rLhs, regCkNull);
    }
    for(ii=0; ii<pList->nExpr; ii++){
      r2 = sqlite3ExprCodeTemp(pParse, pList->a[ii].pExpr, &regToFree);
      if( regCkNull && sqlite3ExprCanBeNull(pList->a[ii].pExpr) ){
        sqlite3VdbeAddOp3(v, OP_BitAnd, regCkNull, r2, regCkNull);
      }
      sqlite3ReleaseTempReg(pParse, regToFree);
      if( ii<pList->nExpr-1 || destIfNull!=destIfFalse ){
        int op = rLhs!=r2 ? OP_Eq : OP_NotNull;
        sqlite3VdbeAddOp4(v, op, rLhs, labelOk, r2,
                          (void*)pColl, P4_COLLSEQ);
        VdbeCoverageIf(v, ii<pList->nExpr-1 && op==OP_Eq);
        VdbeCoverageIf(v, ii==pList->nExpr-1 && op==OP_Eq);
        VdbeCoverageIf(v, ii<pList->nExpr-1 && op==OP_NotNull);
        VdbeCoverageIf(v, ii==pList->nExpr-1 && op==OP_NotNull);
        sqlite3VdbeChangeP5(v, zAff[0]);
      }else{
        int op = rLhs!=r2 ? OP_Ne : OP_IsNull;
        assert( destIfNull==destIfFalse );
        sqlite3VdbeAddOp4(v, op, rLhs, destIfFalse, r2,
                          (void*)pColl, P4_COLLSEQ);
        VdbeCoverageIf(v, op==OP_Ne);
        VdbeCoverageIf(v, op==OP_IsNull);
        sqlite3VdbeChangeP5(v, zAff[0] | SQLITE_JUMPIFNULL);
      }
    }
    if( regCkNull ){
      sqlite3VdbeAddOp2(v, OP_IsNull, regCkNull, destIfNull); VdbeCoverage(v);
      sqlite3VdbeGoto(v, destIfFalse);
    }
    sqlite3VdbeResolveLabel(v, labelOk);
    sqlite3ReleaseTempReg(pParse, regCkNull);
    goto sqlite3ExprCodeIN_finished;
  }

  if( eType!=IN_INDEX_ROWID ){
    /* If this IN operator will use an index, then the order of columns in the
    ** vector might be different from the order in the index.  In that case,
    ** we need to reorder the LHS values to be in index order.  Run Affinity
    ** before reordering the columns, so that the affinity is correct.
    */
    sqlite3VdbeAddOp4(v, OP_Affinity, rLhs, nVector, 0, zAff, nVector);
    for(i=0; i<nVector && aiMap[i]==i; i++){} /* Are LHS fields reordered? */
    if( i!=nVector ){
      /* Need to reorder the LHS fields according to aiMap */
      int rLhsOrig = rLhs;
      rLhs = sqlite3GetTempRange(pParse, nVector);
      for(i=0; i<nVector; i++){
        sqlite3VdbeAddOp3(v, OP_Copy, rLhsOrig+i, rLhs+aiMap[i], 0);
      }
      sqlite3ReleaseTempReg(pParse, rLhsOrig);
    }
  }


  /* Step 2: Check to see if the LHS contains any NULL columns.  If the
  ** LHS does contain NULLs then the result must be either FALSE or NULL.
  ** We will then skip the binary search of the RHS.
  */
  if( destIfNull==destIfFalse ){
    destStep2 = destIfFalse;
  }else{
    destStep2 = destStep6 = sqlite3VdbeMakeLabel(pParse);
  }
  for(i=0; i<nVector; i++){
    Expr *p = sqlite3VectorFieldSubexpr(pExpr->pLeft, i);
    if( pParse->nErr ) goto sqlite3ExprCodeIN_oom_error;
    if( sqlite3ExprCanBeNull(p) ){
      sqlite3VdbeAddOp2(v, OP_IsNull, rLhs+aiMap[i], destStep2);
      VdbeCoverage(v);
    }
  }

  /* Step 3.  The LHS is now known to be non-NULL.  Do the binary search
  ** of the RHS using the LHS as a probe.  If found, the result is
  ** true.
  */
  if( eType==IN_INDEX_ROWID ){
    /* In this case, the RHS is the ROWID of table b-tree and so we also
    ** know that the RHS is non-NULL.  Hence, we combine steps 3 and 4
    ** into a single opcode. */
    assert( nVector==1 );
    sqlite3VdbeAddOp3(v, OP_SeekRowid, iTab, destIfFalse, rLhs);
    VdbeCoverage(v);
    addrTruthOp = sqlite3VdbeAddOp0(v, OP_Goto);  /* Return True */
  }else{
    if( destIfFalse==destIfNull ){
      /* Combine Step 3 and Step 5 into a single opcode */
      if( ExprHasProperty(pExpr, EP_Subrtn) ){
        const VdbeOp *pOp = sqlite3VdbeGetOp(v, pExpr->y.sub.iAddr);
        assert( pOp->opcode==OP_Once || pParse->nErr );
        if( pOp->p3>0 ){  /* tag-202407032019 */
          assert( OptimizationEnabled(pParse->db, SQLITE_BloomFilter)
                 || pParse->nErr );
          sqlite3VdbeAddOp4Int(v, OP_Filter, pOp->p3, destIfFalse,
                               rLhs, nVector); VdbeCoverage(v);
        }
      }
      sqlite3VdbeAddOp4Int(v, OP_NotFound, iTab, destIfFalse,
                           rLhs, nVector); VdbeCoverage(v);
      goto sqlite3ExprCodeIN_finished;
    }
    /* Ordinary Step 3, for the case where FALSE and NULL are distinct */
    addrTruthOp = sqlite3VdbeAddOp4Int(v, OP_Found, iTab, 0,
                                      rLhs, nVector); VdbeCoverage(v);
  }

  /* Step 4.  If the RHS is known to be non-NULL and we did not find
  ** an match on the search above, then the result must be FALSE.
  */
  if( rRhsHasNull && nVector==1 ){
    sqlite3VdbeAddOp2(v, OP_NotNull, rRhsHasNull, destIfFalse);
    VdbeCoverage(v);
  }

  /* Step 5.  If we do not care about the difference between NULL and
  ** FALSE, then just return false.
  */
  if( destIfFalse==destIfNull ) sqlite3VdbeGoto(v, destIfFalse);

  /* Step 6: Loop through rows of the RHS.  Compare each row to the LHS.
  ** If any comparison is NULL, then the result is NULL.  If all
  ** comparisons are FALSE then the final result is FALSE.
  **
  ** For a scalar LHS, it is sufficient to check just the first row
  ** of the RHS.
  */
  if( destStep6 ) sqlite3VdbeResolveLabel(v, destStep6);
  addrTop = sqlite3VdbeAddOp2(v, OP_Rewind, iTab, destIfFalse);
  VdbeCoverage(v);
  if( nVector>1 ){
    destNotNull = sqlite3VdbeMakeLabel(pParse);
  }else{
    /* For nVector==1, combine steps 6 and 7 by immediately returning
    ** FALSE if the first comparison is not NULL */
    destNotNull = destIfFalse;
  }
  for(i=0; i<nVector; i++){
    Expr *p;
    CollSeq *pColl;
    int r3 = sqlite3GetTempReg(pParse);
    p = sqlite3VectorFieldSubexpr(pLeft, i);
    if( ExprUseXSelect(pExpr) ){
      Expr *pRhs = pExpr->x.pSelect->pEList->a[i].pExpr;
      pColl = sqlite3BinaryCompareCollSeq(pParse, p, pRhs);
    }else{
      /* If the RHS of the IN(...) expression are scalar expressions, do
      ** not consider their collation sequences. The documentation says
      ** "The collating sequence used for expressions of the form "x IN (y, z,
      ** ...)" is the collating sequence of x.".  */
      pColl = sqlite3ExprCollSeq(pParse, p);
    }
    sqlite3VdbeAddOp3(v, OP_Column, iTab, aiMap[i], r3);
    sqlite3VdbeAddOp4(v, OP_Ne, rLhs+aiMap[i], destNotNull, r3,
                      (void*)pColl, P4_COLLSEQ);
    VdbeCoverage(v);
    sqlite3ReleaseTempReg(pParse, r3);
  }
  sqlite3VdbeAddOp2(v, OP_Goto, 0, destIfNull);
  if( nVector>1 ){
    sqlite3VdbeResolveLabel(v, destNotNull);
    sqlite3VdbeAddOp2(v, OP_Next, iTab, addrTop+1);
    VdbeCoverage(v);

    /* Step 7:  If we reach this point, we know that the result must
    ** be false. */
    sqlite3VdbeAddOp2(v, OP_Goto, 0, destIfFalse);
  }

  /* Jumps here in order to return true. */
  sqlite3VdbeJumpHere(v, addrTruthOp);

sqlite3ExprCodeIN_finished:
  VdbeComment((v, "end IN expr"));
sqlite3ExprCodeIN_oom_error:
  sqlite3DbFree(pParse->db, aiMap);
  sqlite3DbFree(pParse->db, zAff);
}
#endif /* SQLITE_OMIT_SUBQUERY */

#ifndef SQLITE_OMIT_FLOATING_POINT
/*
** Generate an instruction that will put the floating point
** value described by z[0..n-1] into register iMem.
**
** The z[] string will probably not be zero-terminated.  But the
** z[n] character is guaranteed to be something that does not look
** like the continuation of the number.
*/
static void codeReal(Vdbe *v, const char *z, int negateFlag, int iMem){
  if( ALWAYS(z!=0) ){
    double value;
    sqlite3AtoF(z, &value);
    assert( !sqlite3IsNaN(value) ); /* The new AtoF never returns NaN */
    if( negateFlag ) value = -value;
    sqlite3VdbeAddOp4Dup8(v, OP_Real, 0, iMem, 0, (u8*)&value, P4_REAL);
  }
}
#endif


/*
** Generate an instruction that will put the integer describe by
** text z[0..n-1] into register iMem.
**
** Expr.u.zToken is always UTF8 and zero-terminated.
*/
static void codeInteger(Parse *pParse, Expr *pExpr, int negFlag, int iMem){
  Vdbe *v = pParse->pVdbe;
  if( pExpr->flags & EP_IntValue ){
    int i = pExpr->u.iValue;
    assert( i>=0 );
    if( negFlag ) i = -i;
    sqlite3VdbeAddOp2(v, OP_Integer, i, iMem);
  }else{
    int c;
    i64 value;
    const char *z = pExpr->u.zToken;
    assert( z!=0 );
    c = sqlite3DecOrHexToI64(z, &value);
    if( (c==3 && !negFlag) || (c==2) || (negFlag && value==SMALLEST_INT64)){
#ifdef SQLITE_OMIT_FLOATING_POINT
      sqlite3ErrorMsg(pParse, "oversized integer: %s%#T", negFlag?"-":"",pExpr);
#else
#ifndef SQLITE_OMIT_HEX_INTEGER
      if( sqlite3_strnicmp(z,"0x",2)==0 ){
        sqlite3ErrorMsg(pParse, "hex literal too big: %s%#T",
                        negFlag?"-":"",pExpr);
      }else
#endif
      {
        codeReal(v, z, negFlag, iMem);
      }
#endif
    }else{
      if( negFlag ){ value = c==3 ? SMALLEST_INT64 : -value; }
      sqlite3VdbeAddOp4Dup8(v, OP_Int64, 0, iMem, 0, (u8*)&value, P4_INT64);
    }
  }
}


/* Generate code that will load into register regOut a value that is
** appropriate for the iIdxCol-th column of index pIdx.
*/
void sqlite3ExprCodeLoadIndexColumn(
  Parse *pParse,  /* The parsing context */
  Index *pIdx,    /* The index whose column is to be loaded */
  int iTabCur,    /* Cursor pointing to a table row */
  int iIdxCol,    /* The column of the index to be loaded */
  int regOut      /* Store the index column value in this register */
){
  i16 iTabCol = pIdx->aiColumn[iIdxCol];
  if( iTabCol==XN_EXPR ){
    assert( pIdx->aColExpr );
    assert( pIdx->aColExpr->nExpr>iIdxCol );
    pParse->iSelfTab = iTabCur + 1;
    sqlite3ExprCodeCopy(pParse, pIdx->aColExpr->a[iIdxCol].pExpr, regOut);
    pParse->iSelfTab = 0;
  }else{
    sqlite3ExprCodeGetColumnOfTable(pParse->pVdbe, pIdx->pTable, iTabCur,
                                    iTabCol, regOut);
  }
}

#ifndef SQLITE_OMIT_GENERATED_COLUMNS
/*
** Generate code that will compute the value of generated column pCol
** and store the result in register regOut
*/
void sqlite3ExprCodeGeneratedColumn(
  Parse *pParse,     /* Parsing context */
  Table *pTab,       /* Table containing the generated column */
  Column *pCol,      /* The generated column */
  int regOut         /* Put the result in this register */
){
  int iAddr;
  Vdbe *v = pParse->pVdbe;
  int nErr = pParse->nErr;
  assert( v!=0 );
  assert( pParse->iSelfTab!=0 );
  if( pParse->iSelfTab>0 ){
    iAddr = sqlite3VdbeAddOp3(v, OP_IfNullRow, pParse->iSelfTab-1, 0, regOut);
  }else{
    iAddr = 0;
  }
  sqlite3ExprCodeCopy(pParse, sqlite3ColumnExpr(pTab,pCol), regOut);
  if( (pCol->colFlags & COLFLAG_VIRTUAL)!=0
   && (pTab->tabFlags & TF_Strict)!=0
  ){
    int p3 = 2+(int)(pCol - pTab->aCol);
    sqlite3VdbeAddOp4(v, OP_TypeCheck, regOut, 1, p3, (char*)pTab, P4_TABLE);
  }else if( pCol->affinity>=SQLITE_AFF_TEXT ){
    sqlite3VdbeAddOp4(v, OP_Affinity, regOut, 1, 0, &pCol->affinity, 1);
  }
  if( iAddr ) sqlite3VdbeJumpHere(v, iAddr);
  if( pParse->nErr>nErr ) pParse->db->errByteOffset = -1;
}
#endif /* SQLITE_OMIT_GENERATED_COLUMNS */

/*
** Generate code to extract the value of the iCol-th column of a table.
*/
void sqlite3ExprCodeGetColumnOfTable(
  Vdbe *v,        /* Parsing context */
  Table *pTab,    /* The table containing the value */
  int iTabCur,    /* The table cursor.  Or the PK cursor for WITHOUT ROWID */
  int iCol,       /* Index of the column to extract */
  int regOut      /* Extract the value into this register */
){
  Column *pCol;
  assert( v!=0 );
  assert( pTab!=0 );
  assert( iCol!=XN_EXPR );
  if( iCol<0 || iCol==pTab->iPKey ){
    sqlite3VdbeAddOp2(v, OP_Rowid, iTabCur, regOut);
    VdbeComment((v, "%s.rowid", pTab->zName));
  }else{
    int op;
    int x;
    if( IsVirtual(pTab) ){
      op = OP_VColumn;
      x = iCol;
#ifndef SQLITE_OMIT_GENERATED_COLUMNS
    }else if( (pCol = &pTab->aCol[iCol])->colFlags & COLFLAG_VIRTUAL ){
      Parse *pParse = sqlite3VdbeParser(v);
      if( pCol->colFlags & COLFLAG_BUSY ){
        sqlite3ErrorMsg(pParse, "generated column loop on \"%s\"",
                        pCol->zCnName);
      }else{
        int savedSelfTab = pParse->iSelfTab;
        pCol->colFlags |= COLFLAG_BUSY;
        pParse->iSelfTab = iTabCur+1;
        sqlite3ExprCodeGeneratedColumn(pParse, pTab, pCol, regOut);
        pParse->iSelfTab = savedSelfTab;
        pCol->colFlags &= ~COLFLAG_BUSY;
      }
      return;
#endif
    }else if( !HasRowid(pTab) ){
      testcase( iCol!=sqlite3TableColumnToStorage(pTab, iCol) );
      x = sqlite3TableColumnToIndex(sqlite3PrimaryKeyIndex(pTab), iCol);
      op = OP_Column;
    }else{
      x = sqlite3TableColumnToStorage(pTab,iCol);
      testcase( x!=iCol );
      op = OP_Column;
    }
    sqlite3VdbeAddOp3(v, op, iTabCur, x, regOut);
    sqlite3ColumnDefault(v, pTab, iCol, regOut);
  }
}

/*
** Generate code that will extract the iColumn-th column from
** table pTab and store the column value in register iReg.
**
** There must be an open cursor to pTab in iTable when this routine
** is called.  If iColumn<0 then code is generated that extracts the rowid.
*/
int sqlite3ExprCodeGetColumn(
  Parse *pParse,   /* Parsing and code generating context */
  Table *pTab,     /* Description of the table we are reading from */
  int iColumn,     /* Index of the table column */
  int iTable,      /* The cursor pointing to the table */
  int iReg,        /* Store results here */
  u8 p5            /* P5 value for OP_Column + FLAGS */
){
  assert( pParse->pVdbe!=0 );
  assert( (p5 & (OPFLAG_NOCHNG|OPFLAG_TYPEOFARG|OPFLAG_LENGTHARG))==p5 );
  assert( IsVirtual(pTab) || (p5 & OPFLAG_NOCHNG)==0 );
  sqlite3ExprCodeGetColumnOfTable(pParse->pVdbe, pTab, iTable, iColumn, iReg);
  if( p5 ){
    VdbeOp *pOp = sqlite3VdbeGetLastOp(pParse->pVdbe);
    if( pOp->opcode==OP_Column ) pOp->p5 = p5;
    if( pOp->opcode==OP_VColumn ) pOp->p5 = (p5 & OPFLAG_NOCHNG);
  }
  return iReg;
}

/*
** Generate code to move content from registers iFrom...iFrom+nReg-1
** over to iTo..iTo+nReg-1.
*/
void sqlite3ExprCodeMove(Parse *pParse, int iFrom, int iTo, int nReg){
  sqlite3VdbeAddOp3(pParse->pVdbe, OP_Move, iFrom, iTo, nReg);
}

/*
** Convert a scalar expression node to a TK_REGISTER referencing
** register iReg.  The caller must ensure that iReg already contains
** the correct value for the expression.
*/
void sqlite3ExprToRegister(Expr *pExpr, int iReg){
  Expr *p = sqlite3ExprSkipCollateAndLikely(pExpr);
  if( NEVER(p==0) ) return;
  if( p->op==TK_REGISTER ){
    assert( p->iTable==iReg );
  }else{
    p->op2 = p->op;
    p->op = TK_REGISTER;
    p->iTable = iReg;
    ExprClearProperty(p, EP_Skip);
  }
}

/*
** Evaluate an expression (either a vector or a scalar expression) and store
** the result in contiguous temporary registers.  Return the index of
** the first register used to store the result.
**
** If the returned result register is a temporary scalar, then also write
** that register number into *piFreeable.  If the returned result register
** is not a temporary or if the expression is a vector set *piFreeable
** to 0.
*/
static int exprCodeVector(Parse *pParse, Expr *p, int *piFreeable){
  int iResult;
  int nResult = sqlite3ExprVectorSize(p);
  if( nResult==1 ){
    iResult = sqlite3ExprCodeTemp(pParse, p, piFreeable);
  }else{
    *piFreeable = 0;
    if( p->op==TK_SELECT ){
#if SQLITE_OMIT_SUBQUERY
      iResult = 0;
#else
      iResult = sqlite3CodeSubselect(pParse, p);
#endif
    }else{
      int i;
      iResult = pParse->nMem+1;
      pParse->nMem += nResult;
      assert( ExprUseXList(p) );
      for(i=0; i<nResult; i++){
        sqlite3ExprCodeFactorable(pParse, p->x.pList->a[i].pExpr, i+iResult);
      }
    }
  }
  return iResult;
}

/*
** If the last opcode is a OP_Copy, then set the do-not-merge flag (p5)
** so that a subsequent copy will not be merged into this one.
*/
static void setDoNotMergeFlagOnCopy(Vdbe *v){
  if( sqlite3VdbeGetLastOp(v)->opcode==OP_Copy ){
    sqlite3VdbeChangeP5(v, 1);  /* Tag trailing OP_Copy as not mergeable */
  }
}

/*
** Generate code to implement special SQL functions that are implemented
** in-line rather than by using the usual callbacks.
*/
static int exprCodeInlineFunction(
  Parse *pParse,        /* Parsing context */
  ExprList *pFarg,      /* List of function arguments */
  int iFuncId,          /* Function ID.  One of the INTFUNC_... values */
  int target            /* Store function result in this register */
){
  int nFarg;
  Vdbe *v = pParse->pVdbe;
  assert( v!=0 );
  assert( pFarg!=0 );
  nFarg = pFarg->nExpr;
  assert( nFarg>0 );  /* All in-line functions have at least one argument */
  switch( iFuncId ){
    case INLINEFUNC_coalesce: {
      /* Attempt a direct implementation of the built-in COALESCE() and
      ** IFNULL() functions.  This avoids unnecessary evaluation of
      ** arguments past the first non-NULL argument.
      */
      int endCoalesce = sqlite3VdbeMakeLabel(pParse);
      int i;
      assert( nFarg>=2 );
      sqlite3ExprCode(pParse, pFarg->a[0].pExpr, target);
      for(i=1; i<nFarg; i++){
        sqlite3VdbeAddOp2(v, OP_NotNull, target, endCoalesce);
        VdbeCoverage(v);
        sqlite3ExprCode(pParse, pFarg->a[i].pExpr, target);
      }
      setDoNotMergeFlagOnCopy(v);
      sqlite3VdbeResolveLabel(v, endCoalesce);
      break;
    }
    case INLINEFUNC_iif: {
      Expr caseExpr;
      memset(&caseExpr, 0, sizeof(caseExpr));
      caseExpr.op = TK_CASE;
      caseExpr.x.pList = pFarg;
      return sqlite3ExprCodeTarget(pParse, &caseExpr, target);
    }
#ifdef SQLITE_ENABLE_OFFSET_SQL_FUNC
    case INLINEFUNC_sqlite_offset: {
      Expr *pArg = pFarg->a[0].pExpr;
      if( pArg->op==TK_COLUMN && pArg->iTable>=0 ){
        sqlite3VdbeAddOp3(v, OP_Offset, pArg->iTable, pArg->iColumn, target);
      }else{
        sqlite3VdbeAddOp2(v, OP_Null, 0, target);
      }
      break;
    }
#endif
    default: {  
      /* The UNLIKELY() function is a no-op.  The result is the value
      ** of the first argument.
      */
      assert( nFarg==1 || nFarg==2 );
      target = sqlite3ExprCodeTarget(pParse, pFarg->a[0].pExpr, target);
      break;
    }

  /***********************************************************************
  ** Test-only SQL functions that are only usable if enabled
  ** via SQLITE_TESTCTRL_INTERNAL_FUNCTIONS
  */
#if !defined(SQLITE_UNTESTABLE)
    case INLINEFUNC_expr_compare: {
      /* Compare two expressions using sqlite3ExprCompare() */
      assert( nFarg==2 );
      sqlite3VdbeAddOp2(v, OP_Integer,
         sqlite3ExprCompare(0,pFarg->a[0].pExpr, pFarg->a[1].pExpr,-1),
         target);
      break;
    }

    case INLINEFUNC_expr_implies_expr: {
      /* Compare two expressions using sqlite3ExprImpliesExpr() */
      assert( nFarg==2 );
      sqlite3VdbeAddOp2(v, OP_Integer,
         sqlite3ExprImpliesExpr(pParse,pFarg->a[0].pExpr, pFarg->a[1].pExpr,-1),
         target);
      break;
    }

    case INLINEFUNC_implies_nonnull_row: {
      /* Result of sqlite3ExprImpliesNonNullRow() */
      Expr *pA1;
      assert( nFarg==2 );
      pA1 = pFarg->a[1].pExpr;
      if( pA1->op==TK_COLUMN ){
        sqlite3VdbeAddOp2(v, OP_Integer,
           sqlite3ExprImpliesNonNullRow(pFarg->a[0].pExpr,pA1->iTable,1),
           target);
      }else{
        sqlite3VdbeAddOp2(v, OP_Null, 0, target);
      }
      break;
    }

    case INLINEFUNC_affinity: {
      /* The AFFINITY() function evaluates to a string that describes
      ** the type affinity of the argument.  This is used for testing of
      ** the SQLite type logic.
      */
      const char *azAff[] = { "blob", "text", "numeric", "integer",
                              "real", "flexnum" };
      char aff;
      assert( nFarg==1 );
      aff = sqlite3ExprAffinity(pFarg->a[0].pExpr);
      assert( aff<=SQLITE_AFF_NONE
           || (aff>=SQLITE_AFF_BLOB && aff<=SQLITE_AFF_FLEXNUM) );
      sqlite3VdbeLoadString(v, target,
              (aff<=SQLITE_AFF_NONE) ? "none" : azAff[aff-SQLITE_AFF_BLOB]);
      break;
    }
#endif /* !defined(SQLITE_UNTESTABLE) */
  }
  return target;
}

/*
** Expression Node callback for sqlite3ExprCanReturnSubtype().  If
** pExpr is able to return a subtype, set pWalker->eCode and abort
** the search.  If pExpr can never return a subtype, prune search.
**
** The only expressions that can return a subtype are:
**
**    1.  A function
**    2.  The no-op "+" operator
**    3.  A CASE...END expression
**    4.  A CAST() expression
**    5.  A "expr COLLATE colseq" expression.
**
** For any other kind of expression, prune the search.
**
** For case 1, the expression can yield a subtype if the function has
** the SQLITE_RESULT_SUBTYPE property.  Functions can also return
** a subtype (via sqlite3_result_value()) if any of the arguments can
** return a subtype.
**
** In all cases 1 through 5, the expression might also return a subtype
** if any operand can return a subtype.
*/
static int exprNodeCanReturnSubtype(Walker *pWalker, Expr *pExpr){
  int n;
  FuncDef *pDef;
  sqlite3 *db;
  if( pExpr->op==TK_CASE || pExpr->op==TK_UPLUS 
   || pExpr->op==TK_COLLATE || pExpr->op==TK_CAST 
  ){
    return WRC_Continue;
  }
  if( pExpr->op!=TK_FUNCTION ){
    return WRC_Prune;
  }
  assert( ExprUseXList(pExpr) );
  db = pWalker->pParse->db;
  n = ALWAYS(pExpr->x.pList) ? pExpr->x.pList->nExpr : 0;
  pDef = sqlite3FindFunction(db, pExpr->u.zToken, n, ENC(db), 0);
  if( NEVER(pDef==0) || (pDef->funcFlags & SQLITE_RESULT_SUBTYPE)!=0 ){
    pWalker->eCode = 1;
    return WRC_Abort;
  }
  return WRC_Continue;
}

/*
** Return TRUE if expression pExpr is able to return a subtype.
**
** A TRUE return does not guarantee that a subtype will be returned.
** It only indicates that a subtype return is possible.  False positives
** are acceptable as they only disable an optimization.  False negatives,
** on the other hand, can lead to incorrect answers.
*/
static int sqlite3ExprCanReturnSubtype(Parse *pParse, Expr *pExpr){
  Walker w;
  memset(&w, 0, sizeof(w));
  w.pParse = pParse;
  w.xExprCallback = exprNodeCanReturnSubtype;
  sqlite3WalkExpr(&w, pExpr);
  return w.eCode;
}


/*
** Check to see if pExpr is one of the indexed expressions on pParse->pIdxEpr.
** If it is, then resolve the expression by reading from the index and
** return the register into which the value has been read.  If pExpr is
** not an indexed expression, then return negative.
*/
static SQLITE_NOINLINE int sqlite3IndexedExprLookup(
  Parse *pParse,   /* The parsing context */
  Expr *pExpr,     /* The expression to potentially bypass */
  int target       /* Where to store the result of the expression */
){
  IndexedExpr *p;
  Vdbe *v;
  for(p=pParse->pIdxEpr; p; p=p->pIENext){
    u8 exprAff;
    int iDataCur = p->iDataCur;
    if( iDataCur<0 ) continue;
    if( pParse->iSelfTab ){
      if( p->iDataCur!=pParse->iSelfTab-1 ) continue;
      iDataCur = -1;
    }
    if( sqlite3ExprCompare(0, pExpr, p->pExpr, iDataCur)!=0 ) continue;
    assert( p->aff>=SQLITE_AFF_BLOB && p->aff<=SQLITE_AFF_NUMERIC );
    exprAff = sqlite3ExprAffinity(pExpr);
    if( (exprAff<=SQLITE_AFF_BLOB && p->aff!=SQLITE_AFF_BLOB)
     || (exprAff==SQLITE_AFF_TEXT && p->aff!=SQLITE_AFF_TEXT)
     || (exprAff>=SQLITE_AFF_NUMERIC && p->aff!=SQLITE_AFF_NUMERIC)
    ){
      /* Affinity mismatch on a generated column */
      continue;
    }


    /* Functions that might set a subtype should not be replaced by the
    ** value taken from an expression index if they are themselves an
    ** argument to another scalar function or aggregate. 
    ** https://sqlite.org/forum/forumpost/68d284c86b082c3e */
    if( ExprHasProperty(pExpr, EP_SubtArg)
     && sqlite3ExprCanReturnSubtype(pParse, pExpr) 
    ){
      continue;
    }

    v = pParse->pVdbe;
    assert( v!=0 );
    if( p->bMaybeNullRow ){
      /* If the index is on a NULL row due to an outer join, then we
      ** cannot extract the value from the index.  The value must be
      ** computed using the original expression. */
      int addr = sqlite3VdbeCurrentAddr(v);
      sqlite3VdbeAddOp3(v, OP_IfNullRow, p->iIdxCur, addr+3, target);
      VdbeCoverage(v);
      sqlite3VdbeAddOp3(v, OP_Column, p->iIdxCur, p->iIdxCol, target);
      VdbeComment((v, "%s expr-column %d", p->zIdxName, p->iIdxCol));
      sqlite3VdbeGoto(v, 0);
      p = pParse->pIdxEpr;
      pParse->pIdxEpr = 0;
      sqlite3ExprCode(pParse, pExpr, target);
      pParse->pIdxEpr = p;
      sqlite3VdbeJumpHere(v, addr+2);
    }else{
      sqlite3VdbeAddOp3(v, OP_Column, p->iIdxCur, p->iIdxCol, target);
      VdbeComment((v, "%s expr-column %d", p->zIdxName, p->iIdxCol));
    }
    return target;
  }
  return -1;  /* Not found */
}


/*
** Expression pExpr is guaranteed to be a TK_COLUMN or equivalent. This
** function checks the Parse.pIdxPartExpr list to see if this column
** can be replaced with a constant value. If so, it generates code to
** put the constant value in a register (ideally, but not necessarily, 
** register iTarget) and returns the register number.
**
** Or, if the TK_COLUMN cannot be replaced by a constant, zero is 
** returned.
*/
static int exprPartidxExprLookup(Parse *pParse, Expr *pExpr, int iTarget){
  IndexedExpr *p;
  for(p=pParse->pIdxPartExpr; p; p=p->pIENext){
    if( pExpr->iColumn==p->iIdxCol && pExpr->iTable==p->iDataCur ){
      Vdbe *v = pParse->pVdbe;
      int addr = 0;
      int ret;

      if( p->bMaybeNullRow ){
        addr = sqlite3VdbeAddOp1(v, OP_IfNullRow, p->iIdxCur);
      }
      ret = sqlite3ExprCodeTarget(pParse, p->pExpr, iTarget);
      sqlite3VdbeAddOp4(pParse->pVdbe, OP_Affinity, ret, 1, 0,
                        (const char*)&p->aff, 1);
      if( addr ){
        sqlite3VdbeJumpHere(v, addr);
        sqlite3VdbeChangeP3(v, addr, ret);
      }
      return ret;
    }
  }
  return 0;
}

/*
** Generate code that evaluates an AND or OR operator leaving a
** boolean result in a register.  pExpr is the AND/OR expression.
** Store the result in the "target" register.  Use short-circuit
** evaluation to avoid computing both operands, if possible.
**
** The code generated might require the use of a temporary register.
** If it does, then write the number of that temporary register
** into *pTmpReg.  If not, leave *pTmpReg unchanged.
*/
static SQLITE_NOINLINE int exprCodeTargetAndOr(
  Parse *pParse,     /* Parsing context */
  Expr *pExpr,       /* AND or OR expression to be coded */
  int target,        /* Put result in this register, guaranteed */
  int *pTmpReg       /* Write a temporary register here */
){
  int op;            /* The opcode.  TK_AND or TK_OR */
  int skipOp;        /* Opcode for the branch that skips one operand */
  int addrSkip;      /* Branch instruction that skips one of the operands */
  int regSS = 0;     /* Register holding computed operand when other omitted */
  int r1, r2;        /* Registers for left and right operands, respectively */
  Expr *pAlt;        /* Alternative, simplified expression */
  Vdbe *v;           /* statement being coded */

  assert( pExpr!=0 );
  op = pExpr->op;
  assert( op==TK_AND || op==TK_OR );
  assert( TK_AND==OP_And );            testcase( op==TK_AND );
  assert( TK_OR==OP_Or );              testcase( op==TK_OR );
  assert( pParse->pVdbe!=0 );
  v = pParse->pVdbe;
  pAlt = sqlite3ExprSimplifiedAndOr(pExpr);
  if( pAlt!=pExpr ){
    r1 = sqlite3ExprCodeTarget(pParse, pAlt, target);
    sqlite3VdbeAddOp3(v, OP_And, r1, r1, target);
    return target;
  }
  skipOp = op==TK_AND ? OP_IfNot : OP_If;
  if( exprEvalRhsFirst(pExpr) ){
    /* Compute the right operand first.  Skip the computation of the left
    ** operand if the right operand fully determines the result */
    r2 = regSS = sqlite3ExprCodeTarget(pParse, pExpr->pRight, target);
    addrSkip = sqlite3VdbeAddOp1(v, skipOp, r2);
    VdbeComment((v, "skip left operand"));
    VdbeCoverage(v); 
    r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, pTmpReg);
  }else{
    /* Compute the left operand first */
    r1 = sqlite3ExprCodeTarget(pParse, pExpr->pLeft, target);
    if( ExprHasProperty(pExpr->pRight, EP_Subquery) ){
      /* Skip over the computation of the right operand if the right
      ** operand is a subquery and the left operand completely determines
      ** the result */
      regSS = r1;
      addrSkip = sqlite3VdbeAddOp1(v, skipOp, r1);
      VdbeComment((v, "skip right operand"));
      VdbeCoverage(v);
    }else{
      addrSkip = regSS = 0;
    }
    r2 = sqlite3ExprCodeTemp(pParse, pExpr->pRight, pTmpReg);
  }
  sqlite3VdbeAddOp3(v, op, r2, r1, target);
  testcase( (*pTmpReg)==0 );
  if( addrSkip ){
    sqlite3VdbeAddOp2(v, OP_Goto, 0, sqlite3VdbeCurrentAddr(v)+2);
    sqlite3VdbeJumpHere(v, addrSkip);
    sqlite3VdbeAddOp3(v, OP_Or, regSS, regSS, target);
    VdbeComment((v, "short-circut value"));
  }
  return target;
}



/*
** Generate code into the current Vdbe to evaluate the given
** expression.  Attempt to store the results in register "target".
** Return the register where results are stored.
**
** With this routine, there is no guarantee that results will
** be stored in target.  The result might be stored in some other
** register if it is convenient to do so.  The calling function
** must check the return code and move the results to the desired
** register.
*/
int sqlite3ExprCodeTarget(Parse *pParse, Expr *pExpr, int target){
  Vdbe *v = pParse->pVdbe;  /* The VM under construction */
  int op;                   /* The opcode being coded */
  int inReg = target;       /* Results stored in register inReg */
  int regFree1 = 0;         /* If non-zero free this temporary register */
  int regFree2 = 0;         /* If non-zero free this temporary register */
  int r1, r2;               /* Various register numbers */
  Expr tempX;               /* Temporary expression node */
  int p5 = 0;

  assert( target>0 && target<=pParse->nMem );
  assert( v!=0 );

expr_code_doover:
  if( pExpr==0 ){
    op = TK_NULL;
  }else if( pParse->pIdxEpr!=0
   && !ExprHasProperty(pExpr, EP_Leaf)
   && (r1 = sqlite3IndexedExprLookup(pParse, pExpr, target))>=0
  ){
    return r1;
  }else{
    assert( !ExprHasVVAProperty(pExpr,EP_Immutable) );
    op = pExpr->op;
  }
  assert( op!=TK_ORDER );
  switch( op ){
    case TK_AGG_COLUMN: {
      AggInfo *pAggInfo = pExpr->pAggInfo;
      struct AggInfo_col *pCol;
      assert( pAggInfo!=0 );
      assert( pExpr->iAgg>=0 );
      if( pExpr->iAgg>=pAggInfo->nColumn ){
        /* Happens when the left table of a RIGHT JOIN is null and
        ** is using an expression index */
        sqlite3VdbeAddOp2(v, OP_Null, 0, target);
#ifdef SQLITE_VDBE_COVERAGE
        /* Verify that the OP_Null above is exercised by tests
        ** tag-20230325-2 */
        sqlite3VdbeAddOp3(v, OP_NotNull, target, 1, 20230325);
        VdbeCoverageNeverTaken(v);
#endif
        break;
      }
      pCol = &pAggInfo->aCol[pExpr->iAgg];
      if( !pAggInfo->directMode ){
        return AggInfoColumnReg(pAggInfo, pExpr->iAgg);
      }else if( pAggInfo->useSortingIdx ){
        Table *pTab = pCol->pTab;
        sqlite3VdbeAddOp3(v, OP_Column, pAggInfo->sortingIdxPTab,
                              pCol->iSorterColumn, target);
        if( pTab==0 ){
          /* No comment added */
        }else if( pCol->iColumn<0 ){
          VdbeComment((v,"%s.rowid",pTab->zName));
        }else{
          VdbeComment((v,"%s.%s",
              pTab->zName, pTab->aCol[pCol->iColumn].zCnName));
          if( pTab->aCol[pCol->iColumn].affinity==SQLITE_AFF_REAL ){
            sqlite3VdbeAddOp1(v, OP_RealAffinity, target);
          }
        }
        return target;
      }else if( pExpr->y.pTab==0 ){
        /* This case happens when the argument to an aggregate function
        ** is rewritten by aggregateConvertIndexedExprRefToColumn() */
        sqlite3VdbeAddOp3(v, OP_Column, pExpr->iTable, pExpr->iColumn, target);
        return target;
      }
      /* Otherwise, fall thru into the TK_COLUMN case */
      /* no break */ deliberate_fall_through
    }
    case TK_COLUMN: {
      int iTab = pExpr->iTable;
      int iReg;
      if( ExprHasProperty(pExpr, EP_FixedCol) ){
        /* This COLUMN expression is really a constant due to WHERE clause
        ** constraints, and that constant is coded by the pExpr->pLeft
        ** expression.  However, make sure the constant has the correct
        ** datatype by applying the Affinity of the table column to the
        ** constant.
        */
        int aff;
        iReg = sqlite3ExprCodeTarget(pParse, pExpr->pLeft,target);
        assert( ExprUseYTab(pExpr) );
        assert( pExpr->y.pTab!=0 );
        aff = sqlite3TableColumnAffinity(pExpr->y.pTab, pExpr->iColumn);
        if( aff>SQLITE_AFF_BLOB ){
          static const char zAff[] = "B\000C\000D\000E\000F";
          assert( SQLITE_AFF_BLOB=='A' );
          assert( SQLITE_AFF_TEXT=='B' );
          sqlite3VdbeAddOp4(v, OP_Affinity, iReg, 1, 0,
                            &zAff[(aff-'B')*2], P4_STATIC);
        }
        return iReg;
      }
      if( iTab<0 ){
        if( pParse->iSelfTab<0 ){
          /* Other columns in the same row for CHECK constraints or
          ** generated columns or for inserting into partial index.
          ** The row is unpacked into registers beginning at
          ** 0-(pParse->iSelfTab).  The rowid (if any) is in a register
          ** immediately prior to the first column.
          */
          Column *pCol;
          Table *pTab;
          int iSrc;
          int iCol = pExpr->iColumn;
          assert( ExprUseYTab(pExpr) );
          pTab = pExpr->y.pTab;
          assert( pTab!=0 );
          assert( iCol>=XN_ROWID );
          assert( iCol<pTab->nCol );
          if( iCol<0 ){
            return -1-pParse->iSelfTab;
          }
          pCol = pTab->aCol + iCol;
          testcase( iCol!=sqlite3TableColumnToStorage(pTab,iCol) );
          iSrc = sqlite3TableColumnToStorage(pTab, iCol) - pParse->iSelfTab;
#ifndef SQLITE_OMIT_GENERATED_COLUMNS
          if( pCol->colFlags & COLFLAG_GENERATED ){
            if( pCol->colFlags & COLFLAG_BUSY ){
              sqlite3ErrorMsg(pParse, "generated column loop on \"%s\"",
                              pCol->zCnName);
              return 0;
            }
            pCol->colFlags |= COLFLAG_BUSY;
            if( pCol->colFlags & COLFLAG_NOTAVAIL ){
              sqlite3ExprCodeGeneratedColumn(pParse, pTab, pCol, iSrc);
            }
            pCol->colFlags &= ~(COLFLAG_BUSY|COLFLAG_NOTAVAIL);
            return iSrc;
          }else
#endif /* SQLITE_OMIT_GENERATED_COLUMNS */
          if( pCol->affinity==SQLITE_AFF_REAL ){
            sqlite3VdbeAddOp2(v, OP_SCopy, iSrc, target);
            sqlite3VdbeAddOp1(v, OP_RealAffinity, target);
            return target;
          }else{
            return iSrc;
          }
        }else{
          /* Coding an expression that is part of an index where column names
          ** in the index refer to the table to which the index belongs */
          iTab = pParse->iSelfTab - 1;
        }
      }
      else if( pParse->pIdxPartExpr 
       && 0!=(r1 = exprPartidxExprLookup(pParse, pExpr, target))
      ){
        return r1;
      }
      assert( ExprUseYTab(pExpr) );
      assert( pExpr->y.pTab!=0 );
      iReg = sqlite3ExprCodeGetColumn(pParse, pExpr->y.pTab,
                               pExpr->iColumn, iTab, target,
                               pExpr->op2);
      return iReg;
    }
    case TK_INTEGER: {
      codeInteger(pParse, pExpr, 0, target);
      return target;
    }
    case TK_TRUEFALSE: {
      sqlite3VdbeAddOp2(v, OP_Integer, sqlite3ExprTruthValue(pExpr), target);
      return target;
    }
#ifndef SQLITE_OMIT_FLOATING_POINT
    case TK_FLOAT: {
      assert( !ExprHasProperty(pExpr, EP_IntValue) );
      codeReal(v, pExpr->u.zToken, 0, target);
      return target;
    }
#endif
    case TK_STRING: {
      assert( !ExprHasProperty(pExpr, EP_IntValue) );
      sqlite3VdbeLoadString(v, target, pExpr->u.zToken);
      return target;
    }
    case TK_NULLS: {
      /* Set a range of registers to NULL.  pExpr->y.nReg registers starting
      ** with target */
      sqlite3VdbeAddOp3(v, OP_Null, 0, target, target + pExpr->y.nReg - 1);
      return target;
    }
    default: {
      /* Make NULL the default case so that if a bug causes an illegal
      ** Expr node to be passed into this function, it will be handled
      ** sanely and not crash.  But keep the assert() to bring the problem
      ** to the attention of the developers. */
      assert( op==TK_NULL || op==TK_ERROR || pParse->db->mallocFailed );
      sqlite3VdbeAddOp2(v, OP_Null, 0, target);
      return target;
    }
#ifndef SQLITE_OMIT_BLOB_LITERAL
    case TK_BLOB: {
      int n;
      const char *z;
      char *zBlob;
      assert( !ExprHasProperty(pExpr, EP_IntValue) );
      assert( pExpr->u.zToken[0]=='x' || pExpr->u.zToken[0]=='X' );
      assert( pExpr->u.zToken[1]=='\'' );
      z = &pExpr->u.zToken[2];
      n = sqlite3Strlen30(z) - 1;
      assert( z[n]=='\'' );
      zBlob = sqlite3HexToBlob(sqlite3VdbeDb(v), z, n);
      sqlite3VdbeAddOp4(v, OP_Blob, n/2, target, 0, zBlob, P4_DYNAMIC);
      return target;
    }
#endif
    case TK_VARIABLE: {
      assert( !ExprHasProperty(pExpr, EP_IntValue) );
      assert( pExpr->u.zToken!=0 );
      assert( pExpr->u.zToken[0]!=0 );
      sqlite3VdbeAddOp2(v, OP_Variable, pExpr->iColumn, target);
      return target;
    }
    case TK_REGISTER: {
      return pExpr->iTable;
    }
#ifndef SQLITE_OMIT_CAST
    case TK_CAST: {
      /* Expressions of the form:   CAST(pLeft AS token) */
      sqlite3ExprCode(pParse, pExpr->pLeft, target);
      assert( inReg==target );
      assert( !ExprHasProperty(pExpr, EP_IntValue) );
      sqlite3VdbeAddOp2(v, OP_Cast, target,
                        sqlite3AffinityType(pExpr->u.zToken, 0));
      return inReg;
    }
#endif /* SQLITE_OMIT_CAST */
    case TK_IS:
    case TK_ISNOT:
      op = (op==TK_IS) ? TK_EQ : TK_NE;
      p5 = SQLITE_NULLEQ;
      /* no break */ deliberate_fall_through
    case TK_LT:
    case TK_LE:
    case TK_GT:
    case TK_GE:
    case TK_NE:
    case TK_EQ: {
      Expr *pLeft = pExpr->pLeft;
      int addrIsNull = 0;
      if( sqlite3ExprIsVector(pLeft) ){
        codeVectorCompare(pParse, pExpr, target, op, p5);
      }else{
        if( ExprHasProperty(pExpr, EP_Subquery) && p5!=SQLITE_NULLEQ ){
          addrIsNull = exprComputeOperands(pParse, pExpr,
                                     &r1, &r2, &regFree1, &regFree2);
        }else{
          r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree1);
          r2 = sqlite3ExprCodeTemp(pParse, pExpr->pRight, &regFree2);
        }
        sqlite3VdbeAddOp2(v, OP_Integer, 1, inReg);
        codeCompare(pParse, pLeft, pExpr->pRight, op, r1, r2,
            sqlite3VdbeCurrentAddr(v)+2, p5,
            ExprHasProperty(pExpr,EP_Commuted));
        assert(TK_LT==OP_Lt); testcase(op==OP_Lt); VdbeCoverageIf(v,op==OP_Lt);
        assert(TK_LE==OP_Le); testcase(op==OP_Le); VdbeCoverageIf(v,op==OP_Le);
        assert(TK_GT==OP_Gt); testcase(op==OP_Gt); VdbeCoverageIf(v,op==OP_Gt);
        assert(TK_GE==OP_Ge); testcase(op==OP_Ge); VdbeCoverageIf(v,op==OP_Ge);
        assert(TK_EQ==OP_Eq); testcase(op==OP_Eq); VdbeCoverageIf(v,op==OP_Eq);
        assert(TK_NE==OP_Ne); testcase(op==OP_Ne); VdbeCoverageIf(v,op==OP_Ne);
        if( p5==SQLITE_NULLEQ ){
          sqlite3VdbeAddOp2(v, OP_Integer, 0, inReg);
        }else{
          sqlite3VdbeAddOp3(v, OP_ZeroOrNull, r1, inReg, r2);
          if( addrIsNull ){
            sqlite3VdbeAddOp2(v, OP_Goto, 0, sqlite3VdbeCurrentAddr(v)+2);
            sqlite3VdbeJumpHere(v, addrIsNull);
            sqlite3VdbeAddOp2(v, OP_Null, 0, inReg);
          }
        }
        testcase( regFree1==0 );
        testcase( regFree2==0 );
      }
      break;
    }
    case TK_AND:
    case TK_OR: {
      inReg = exprCodeTargetAndOr(pParse, pExpr, target, &regFree1);
      break;
    }
    case TK_PLUS:
    case TK_STAR:
    case TK_MINUS:
    case TK_REM:
    case TK_BITAND:
    case TK_BITOR:
    case TK_SLASH:
    case TK_LSHIFT:
    case TK_RSHIFT:
    case TK_CONCAT: {
      int addrIsNull;
      assert( TK_PLUS==OP_Add );           testcase( op==TK_PLUS );
      assert( TK_MINUS==OP_Subtract );     testcase( op==TK_MINUS );
      assert( TK_REM==OP_Remainder );      testcase( op==TK_REM );
      assert( TK_BITAND==OP_BitAnd );      testcase( op==TK_BITAND );
      assert( TK_BITOR==OP_BitOr );        testcase( op==TK_BITOR );
      assert( TK_SLASH==OP_Divide );       testcase( op==TK_SLASH );
      assert( TK_LSHIFT==OP_ShiftLeft );   testcase( op==TK_LSHIFT );
      assert( TK_RSHIFT==OP_ShiftRight );  testcase( op==TK_RSHIFT );
      assert( TK_CONCAT==OP_Concat );      testcase( op==TK_CONCAT );
      if( ExprHasProperty(pExpr, EP_Subquery) ){
        addrIsNull = exprComputeOperands(pParse, pExpr,
                                   &r1, &r2, &regFree1, &regFree2);
      }else{
        r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree1);
        r2 = sqlite3ExprCodeTemp(pParse, pExpr->pRight, &regFree2);
        addrIsNull = 0;
      }
      sqlite3VdbeAddOp3(v, op, r2, r1, target);
      testcase( regFree1==0 );
      testcase( regFree2==0 );
      if( addrIsNull ){
        sqlite3VdbeAddOp2(v, OP_Goto, 0, sqlite3VdbeCurrentAddr(v)+2);
        sqlite3VdbeJumpHere(v, addrIsNull);
        sqlite3VdbeAddOp2(v, OP_Null, 0, target);
        VdbeComment((v, "short-circut value"));
      }
      break;
    }
    case TK_UMINUS: {
      Expr *pLeft = pExpr->pLeft;
      assert( pLeft );
      if( pLeft->op==TK_INTEGER ){
        codeInteger(pParse, pLeft, 1, target);
        return target;
#ifndef SQLITE_OMIT_FLOATING_POINT
      }else if( pLeft->op==TK_FLOAT ){
        assert( !ExprHasProperty(pExpr, EP_IntValue) );
        codeReal(v, pLeft->u.zToken, 1, target);
        return target;
#endif
      }else{
        tempX.op = TK_INTEGER;
        tempX.flags = EP_IntValue|EP_TokenOnly;
        tempX.u.iValue = 0;
        ExprClearVVAProperties(&tempX);
        r1 = sqlite3ExprCodeTemp(pParse, &tempX, &regFree1);
        r2 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree2);
        sqlite3VdbeAddOp3(v, OP_Subtract, r2, r1, target);
        testcase( regFree2==0 );
      }
      break;
    }
    case TK_BITNOT:
    case TK_NOT: {
      assert( TK_BITNOT==OP_BitNot );   testcase( op==TK_BITNOT );
      assert( TK_NOT==OP_Not );         testcase( op==TK_NOT );
      r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree1);
      testcase( regFree1==0 );
      sqlite3VdbeAddOp2(v, op, r1, inReg);
      break;
    }
    case TK_TRUTH: {
      int isTrue;    /* IS TRUE or IS NOT TRUE */
      int bNormal;   /* IS TRUE or IS FALSE */
      r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree1);
      testcase( regFree1==0 );
      isTrue = sqlite3ExprTruthValue(pExpr->pRight);
      bNormal = pExpr->op2==TK_IS;
      testcase( isTrue && bNormal);
      testcase( !isTrue && bNormal);
      sqlite3VdbeAddOp4Int(v, OP_IsTrue, r1, inReg, !isTrue, isTrue ^ bNormal);
      break;
    }
    case TK_ISNULL:
    case TK_NOTNULL: {
      int addr;
      assert( TK_ISNULL==OP_IsNull );   testcase( op==TK_ISNULL );
      assert( TK_NOTNULL==OP_NotNull ); testcase( op==TK_NOTNULL );
      sqlite3VdbeAddOp2(v, OP_Integer, 1, target);
      r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree1);
      testcase( regFree1==0 );
      addr = sqlite3VdbeAddOp1(v, op, r1);
      VdbeCoverageIf(v, op==TK_ISNULL);
      VdbeCoverageIf(v, op==TK_NOTNULL);
      sqlite3VdbeAddOp2(v, OP_Integer, 0, target);
      sqlite3VdbeJumpHere(v, addr);
      break;
    }
    case TK_AGG_FUNCTION: {
      AggInfo *pInfo = pExpr->pAggInfo;
      if( pInfo==0
       || NEVER(pExpr->iAgg<0)
       || NEVER(pExpr->iAgg>=pInfo->nFunc)
      ){
        assert( !ExprHasProperty(pExpr, EP_IntValue) );
        sqlite3ErrorMsg(pParse, "misuse of aggregate: %#T()", pExpr);
      }else{
        return AggInfoFuncReg(pInfo, pExpr->iAgg);
      }
      break;
    }
    case TK_FUNCTION: {
      ExprList *pFarg;       /* List of function arguments */
      int nFarg;             /* Number of function arguments */
      FuncDef *pDef;         /* The function definition object */
      const char *zId;       /* The function name */
      u32 constMask = 0;     /* Mask of function arguments that are constant */
      int i;                 /* Loop counter */
      sqlite3 *db = pParse->db;  /* The database connection */
      u8 enc = ENC(db);      /* The text encoding used by this database */
      CollSeq *pColl = 0;    /* A collating sequence */

#ifndef SQLITE_OMIT_WINDOWFUNC
      if( ExprHasProperty(pExpr, EP_WinFunc) ){
        return pExpr->y.pWin->regResult;
      }
#endif

      if( ConstFactorOk(pParse)
       && sqlite3ExprIsConstantNotJoin(pParse,pExpr)
      ){
        /* SQL functions can be expensive. So try to avoid running them
        ** multiple times if we know they always give the same result */
        return sqlite3ExprCodeRunJustOnce(pParse, pExpr, -1);
      }
      assert( !ExprHasProperty(pExpr, EP_TokenOnly) );
      assert( ExprUseXList(pExpr) );
      pFarg = pExpr->x.pList;
      nFarg = pFarg ? pFarg->nExpr : 0;
      assert( !ExprHasProperty(pExpr, EP_IntValue) );
      zId = pExpr->u.zToken;
      pDef = sqlite3FindFunction(db, zId, nFarg, enc, 0);
#ifdef SQLITE_ENABLE_UNKNOWN_SQL_FUNCTION
      if( pDef==0 && pParse->explain ){
        pDef = sqlite3FindFunction(db, "unknown", nFarg, enc, 0);
      }
#endif
      if( pDef==0 || pDef->xFinalize!=0 ){
        sqlite3ErrorMsg(pParse, "unknown function: %#T()", pExpr);
        break;
      }
      if( (pDef->funcFlags & SQLITE_FUNC_INLINE)!=0 && ALWAYS(pFarg!=0) ){
        assert( (pDef->funcFlags & SQLITE_FUNC_UNSAFE)==0 );
        assert( (pDef->funcFlags & SQLITE_FUNC_DIRECT)==0 );
        return exprCodeInlineFunction(pParse, pFarg,
             SQLITE_PTR_TO_INT(pDef->pUserData), target);
      }else if( pDef->funcFlags & (SQLITE_FUNC_DIRECT|SQLITE_FUNC_UNSAFE) ){
        sqlite3ExprFunctionUsable(pParse, pExpr, pDef);
      }

      for(i=0; i<nFarg; i++){
        if( i<32 && sqlite3ExprIsConstant(pParse, pFarg->a[i].pExpr) ){
          testcase( i==31 );
          constMask |= MASKBIT32(i);
        }
        if( (pDef->funcFlags & SQLITE_FUNC_NEEDCOLL)!=0 && !pColl ){
          pColl = sqlite3ExprCollSeq(pParse, pFarg->a[i].pExpr);
        }
      }
      if( pFarg ){
        if( constMask ){
          r1 = pParse->nMem+1;
          pParse->nMem += nFarg;
        }else{
          r1 = sqlite3GetTempRange(pParse, nFarg);
        }

        /* For length() and typeof() and octet_length() functions,
        ** set the P5 parameter to the OP_Column opcode to OPFLAG_LENGTHARG
        ** or OPFLAG_TYPEOFARG or OPFLAG_BYTELENARG respectively, to avoid
        ** unnecessary data loading.
        */
        if( (pDef->funcFlags & (SQLITE_FUNC_LENGTH|SQLITE_FUNC_TYPEOF))!=0 ){
          u8 exprOp;
          assert( nFarg==1 );
          assert( pFarg->a[0].pExpr!=0 );
          exprOp = pFarg->a[0].pExpr->op;
          if( exprOp==TK_COLUMN || exprOp==TK_AGG_COLUMN ){
            assert( SQLITE_FUNC_LENGTH==OPFLAG_LENGTHARG );
            assert( SQLITE_FUNC_TYPEOF==OPFLAG_TYPEOFARG );
            assert( SQLITE_FUNC_BYTELEN==OPFLAG_BYTELENARG );
            assert( (OPFLAG_LENGTHARG|OPFLAG_TYPEOFARG)==OPFLAG_BYTELENARG );
            testcase( (pDef->funcFlags & OPFLAG_BYTELENARG)==OPFLAG_LENGTHARG );
            testcase( (pDef->funcFlags & OPFLAG_BYTELENARG)==OPFLAG_TYPEOFARG );
            testcase( (pDef->funcFlags & OPFLAG_BYTELENARG)==OPFLAG_BYTELENARG);
            pFarg->a[0].pExpr->op2 = pDef->funcFlags & OPFLAG_BYTELENARG;
          }
        }

        sqlite3ExprCodeExprList(pParse, pFarg, r1, 0, SQLITE_ECEL_FACTOR);
      }else{
        r1 = 0;
      }
#ifndef SQLITE_OMIT_VIRTUALTABLE
      /* Possibly overload the function if the first argument is
      ** a virtual table column.
      **
      ** For infix functions (LIKE, GLOB, REGEXP, and MATCH) use the
      ** second argument, not the first, as the argument to test to
      ** see if it is a column in a virtual table.  This is done because
      ** the left operand of infix functions (the operand we want to
      ** control overloading) ends up as the second argument to the
      ** function.  The expression "A glob B" is equivalent to
      ** "glob(B,A).  We want to use the A in "A glob B" to test
      ** for function overloading.  But we use the B term in "glob(B,A)".
      */
      if( nFarg>=2 && ExprHasProperty(pExpr, EP_InfixFunc) ){
        pDef = sqlite3VtabOverloadFunction(db, pDef, nFarg, pFarg->a[1].pExpr);
      }else if( nFarg>0 ){
        pDef = sqlite3VtabOverloadFunction(db, pDef, nFarg, pFarg->a[0].pExpr);
      }
#endif
      if( pDef->funcFlags & SQLITE_FUNC_NEEDCOLL ){
        if( !pColl ) pColl = db->pDfltColl;
        sqlite3VdbeAddOp4(v, OP_CollSeq, 0, 0, 0, (char *)pColl, P4_COLLSEQ);
      }
      sqlite3VdbeAddFunctionCall(pParse, constMask, r1, target, nFarg,
                                 pDef, pExpr->op2);
      if( nFarg ){
        if( constMask==0 ){
          sqlite3ReleaseTempRange(pParse, r1, nFarg);
        }else{
          sqlite3VdbeReleaseRegisters(pParse, r1, nFarg, constMask, 1);
        }
      }
      return target;
    }
#ifndef SQLITE_OMIT_SUBQUERY
    case TK_EXISTS:
    case TK_SELECT: {
      int nCol;
      testcase( op==TK_EXISTS );
      testcase( op==TK_SELECT );
      if( pParse->db->mallocFailed ){
        return 0;
      }else if( op==TK_SELECT
             && ALWAYS( ExprUseXSelect(pExpr) )
             && (nCol = pExpr->x.pSelect->pEList->nExpr)!=1
      ){
        sqlite3SubselectError(pParse, nCol, 1);
      }else{
        return sqlite3CodeSubselect(pParse, pExpr);
      }
      break;
    }
    case TK_SELECT_COLUMN: {
      int n;
      Expr *pLeft = pExpr->pLeft;
      if( pLeft->iTable==0 || pParse->withinRJSubrtn > pLeft->op2 ){
        pLeft->iTable = sqlite3CodeSubselect(pParse, pLeft);
        pLeft->op2 = pParse->withinRJSubrtn;
      }
      assert( pLeft->op==TK_SELECT || pLeft->op==TK_ERROR );
      n = sqlite3ExprVectorSize(pLeft);
      if( pExpr->iTable!=n ){
        sqlite3ErrorMsg(pParse, "%d columns assigned %d values",
                                pExpr->iTable, n);
      }
      return pLeft->iTable + pExpr->iColumn;
    }
    case TK_IN: {
      int destIfFalse = sqlite3VdbeMakeLabel(pParse);
      int destIfNull = sqlite3VdbeMakeLabel(pParse);
      sqlite3VdbeAddOp2(v, OP_Null, 0, target);
      sqlite3ExprCodeIN(pParse, pExpr, destIfFalse, destIfNull);
      sqlite3VdbeAddOp2(v, OP_Integer, 1, target);
      sqlite3VdbeResolveLabel(v, destIfFalse);
      sqlite3VdbeAddOp2(v, OP_AddImm, target, 0);
      sqlite3VdbeResolveLabel(v, destIfNull);
      return target;
    }
#endif /* SQLITE_OMIT_SUBQUERY */


    /*
    **    x BETWEEN y AND z
    **
    ** This is equivalent to
    **
    **    x>=y AND x<=z
    **
    ** X is stored in pExpr->pLeft.
    ** Y is stored in pExpr->pList->a[0].pExpr.
    ** Z is stored in pExpr->pList->a[1].pExpr.
    */
    case TK_BETWEEN: {
      exprCodeBetween(pParse, pExpr, target, 0, 0);
      return target;
    }
    case TK_COLLATE: {
      if( !ExprHasProperty(pExpr, EP_Collate) ){
        /* A TK_COLLATE Expr node without the EP_Collate tag is a so-called
        ** "SOFT-COLLATE" that is added to constraints that are pushed down
        ** from outer queries into sub-queries by the WHERE-clause push-down
        ** optimization. Clear subtypes as subtypes may not cross a subquery
        ** boundary.
        */
        assert( pExpr->pLeft );
        sqlite3ExprCode(pParse, pExpr->pLeft, target);
        sqlite3VdbeAddOp1(v, OP_ClrSubtype, target);
        return target;
      }else{
        pExpr = pExpr->pLeft;
        goto expr_code_doover; /* 2018-04-28: Prevent deep recursion. */
      }
    }
    case TK_SPAN:
    case TK_UPLUS: {
      pExpr = pExpr->pLeft;
      goto expr_code_doover; /* 2018-04-28: Prevent deep recursion. OSSFuzz. */
    }

    case TK_TRIGGER: {
      /* If the opcode is TK_TRIGGER, then the expression is a reference
      ** to a column in the new.* or old.* pseudo-tables available to
      ** trigger programs. In this case Expr.iTable is set to 1 for the
      ** new.* pseudo-table, or 0 for the old.* pseudo-table. Expr.iColumn
      ** is set to the column of the pseudo-table to read, or to -1 to
      ** read the rowid field.
      **
      ** The expression is implemented using an OP_Param opcode. The p1
      ** parameter is set to 0 for an old.rowid reference, or to (i+1)
      ** to reference another column of the old.* pseudo-table, where
      ** i is the index of the column. For a new.rowid reference, p1 is
      ** set to (n+1), where n is the number of columns in each pseudo-table.
      ** For a reference to any other column in the new.* pseudo-table, p1
      ** is set to (n+2+i), where n and i are as defined previously. For
      ** example, if the table on which triggers are being fired is
      ** declared as:
      **
      **   CREATE TABLE t1(a, b);
      **
      ** Then p1 is interpreted as follows:
      **
      **   p1==0   ->    old.rowid     p1==3   ->    new.rowid
      **   p1==1   ->    old.a         p1==4   ->    new.a
      **   p1==2   ->    old.b         p1==5   ->    new.b      
      */
      Table *pTab;
      int iCol;
      int p1;

      assert( ExprUseYTab(pExpr) );
      pTab = pExpr->y.pTab;
      iCol = pExpr->iColumn;
      p1 = pExpr->iTable * (pTab->nCol+1) + 1
                     + sqlite3TableColumnToStorage(pTab, iCol);

      assert( pExpr->iTable==0 || pExpr->iTable==1 );
      assert( iCol>=-1 && iCol<pTab->nCol );
      assert( pTab->iPKey<0 || iCol!=pTab->iPKey );
      assert( p1>=0 && p1<(pTab->nCol*2+2) );

      sqlite3VdbeAddOp2(v, OP_Param, p1, target);
      VdbeComment((v, "r[%d]=%s.%s", target,
        (pExpr->iTable ? "new" : "old"),
        (pExpr->iColumn<0 ? "rowid" : pExpr->y.pTab->aCol[iCol].zCnName)
      ));

#ifndef SQLITE_OMIT_FLOATING_POINT
      /* If the column has REAL affinity, it may currently be stored as an
      ** integer. Use OP_RealAffinity to make sure it is really real.
      **
      ** EVIDENCE-OF: R-60985-57662 SQLite will convert the value back to
      ** floating point when extracting it from the record.  */
      if( iCol>=0 && pTab->aCol[iCol].affinity==SQLITE_AFF_REAL ){
        sqlite3VdbeAddOp1(v, OP_RealAffinity, target);
      }
#endif
      break;
    }

    case TK_VECTOR: {
      sqlite3ErrorMsg(pParse, "row value misused");
      break;
    }

    /* TK_IF_NULL_ROW Expr nodes are inserted ahead of expressions
    ** that derive from the right-hand table of a LEFT JOIN.  The
    ** Expr.iTable value is the table number for the right-hand table.
    ** The expression is only evaluated if that table is not currently
    ** on a LEFT JOIN NULL row.
    */
    case TK_IF_NULL_ROW: {
      int addrINR;
      u8 okConstFactor = pParse->okConstFactor;
      AggInfo *pAggInfo = pExpr->pAggInfo;
      if( pAggInfo ){
        assert( pExpr->iAgg>=0 && pExpr->iAgg<pAggInfo->nColumn );
        if( !pAggInfo->directMode ){
          inReg = AggInfoColumnReg(pAggInfo, pExpr->iAgg);
          break;
        }
        if( pExpr->pAggInfo->useSortingIdx ){
          sqlite3VdbeAddOp3(v, OP_Column, pAggInfo->sortingIdxPTab,
                            pAggInfo->aCol[pExpr->iAgg].iSorterColumn,
                            target);
          inReg = target;
          break;
        }
      }
      addrINR = sqlite3VdbeAddOp3(v, OP_IfNullRow, pExpr->iTable, 0, target);
      /* The OP_IfNullRow opcode above can overwrite the result register with
      ** NULL.  So we have to ensure that the result register is not a value
      ** that is suppose to be a constant.  Two defenses are needed:
      **   (1)  Temporarily disable factoring of constant expressions
      **   (2)  Make sure the computed value really is stored in register
      **        "target" and not someplace else.
      */
      pParse->okConstFactor = 0;   /* note (1) above */
      sqlite3ExprCode(pParse, pExpr->pLeft, target);
      assert( target==inReg );
      pParse->okConstFactor = okConstFactor;
      sqlite3VdbeJumpHere(v, addrINR);
      break;
    }

    /*
    ** Form A:
    **   CASE x WHEN e1 THEN r1 WHEN e2 THEN r2 ... WHEN eN THEN rN ELSE y END
    **
    ** Form B:
    **   CASE WHEN e1 THEN r1 WHEN e2 THEN r2 ... WHEN eN THEN rN ELSE y END
    **
    ** Form A is can be transformed into the equivalent form B as follows:
    **   CASE WHEN x=e1 THEN r1 WHEN x=e2 THEN r2 ...
    **        WHEN x=eN THEN rN ELSE y END
    **
    ** X (if it exists) is in pExpr->pLeft.
    ** Y is in the last element of pExpr->x.pList if pExpr->x.pList->nExpr is
    ** odd.  The Y is also optional.  If the number of elements in x.pList
    ** is even, then Y is omitted and the "otherwise" result is NULL.
    ** Ei is in pExpr->pList->a[i*2] and Ri is pExpr->pList->a[i*2+1].
    **
    ** The result of the expression is the Ri for the first matching Ei,
    ** or if there is no matching Ei, the ELSE term Y, or if there is
    ** no ELSE term, NULL.
    */
    case TK_CASE: {
      int endLabel;                     /* GOTO label for end of CASE stmt */
      int nextCase;                     /* GOTO label for next WHEN clause */
      int nExpr;                        /* 2x number of WHEN terms */
      int i;                            /* Loop counter */
      ExprList *pEList;                 /* List of WHEN terms */
      struct ExprList_item *aListelem;  /* Array of WHEN terms */
      Expr opCompare;                   /* The X==Ei expression */
      Expr *pX;                         /* The X expression */
      Expr *pTest = 0;                  /* X==Ei (form A) or just Ei (form B) */
      Expr *pDel = 0;
      sqlite3 *db = pParse->db;

      assert( ExprUseXList(pExpr) && pExpr->x.pList!=0 );
      assert(pExpr->x.pList->nExpr > 0);
      pEList = pExpr->x.pList;
      aListelem = pEList->a;
      nExpr = pEList->nExpr;
      endLabel = sqlite3VdbeMakeLabel(pParse);
      if( (pX = pExpr->pLeft)!=0 ){
        pDel = sqlite3ExprDup(db, pX, 0);
        if( db->mallocFailed ){
          sqlite3ExprDelete(db, pDel);
          break;
        }
        testcase( pX->op==TK_COLUMN );
        sqlite3ExprToRegister(pDel, exprCodeVector(pParse, pDel, &regFree1));
        testcase( regFree1==0 );
        memset(&opCompare, 0, sizeof(opCompare));
        opCompare.op = TK_EQ;
        opCompare.pLeft = pDel;
        pTest = &opCompare;
        /* Ticket b351d95f9cd5ef17e9d9dbae18f5ca8611190001:
        ** The value in regFree1 might get SCopy-ed into the file result.
        ** So make sure that the regFree1 register is not reused for other
        ** purposes and possibly overwritten.  */
        regFree1 = 0;
      }
      for(i=0; i<nExpr-1; i=i+2){
        if( pX ){
          assert( pTest!=0 );
          opCompare.pRight = aListelem[i].pExpr;
        }else{
          pTest = aListelem[i].pExpr;
        }
        nextCase = sqlite3VdbeMakeLabel(pParse);
        testcase( pTest->op==TK_COLUMN );
        sqlite3ExprIfFalse(pParse, pTest, nextCase, SQLITE_JUMPIFNULL);
        testcase( aListelem[i+1].pExpr->op==TK_COLUMN );
        sqlite3ExprCode(pParse, aListelem[i+1].pExpr, target);
        sqlite3VdbeGoto(v, endLabel);
        sqlite3VdbeResolveLabel(v, nextCase);
      }
      if( (nExpr&1)!=0 ){
        sqlite3ExprCode(pParse, pEList->a[nExpr-1].pExpr, target);
      }else{
        sqlite3VdbeAddOp2(v, OP_Null, 0, target);
      }
      sqlite3ExprDelete(db, pDel);
      setDoNotMergeFlagOnCopy(v);
      sqlite3VdbeResolveLabel(v, endLabel);
      break;
    }
#ifndef SQLITE_OMIT_TRIGGER
    case TK_RAISE: {
      assert( pExpr->affExpr==OE_Rollback
           || pExpr->affExpr==OE_Abort
           || pExpr->affExpr==OE_Fail
           || pExpr->affExpr==OE_Ignore
      );
      if( !pParse->pTriggerTab && !pParse->nested ){
        sqlite3ErrorMsg(pParse,
                       "RAISE() may only be used within a trigger-program");
        return 0;
      }
      if( pExpr->affExpr==OE_Abort ){
        sqlite3MayAbort(pParse);
      }
      assert( !ExprHasProperty(pExpr, EP_IntValue) );
      if( pExpr->affExpr==OE_Ignore ){
        sqlite3VdbeAddOp2(v, OP_Halt, SQLITE_OK, OE_Ignore);
        VdbeCoverage(v);
      }else{
        r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree1);
        sqlite3VdbeAddOp3(v, OP_Halt, 
             pParse->pTriggerTab ? SQLITE_CONSTRAINT_TRIGGER : SQLITE_ERROR,
             pExpr->affExpr, r1);
      }
      break;
    }
#endif
  }
  sqlite3ReleaseTempReg(pParse, regFree1);
  sqlite3ReleaseTempReg(pParse, regFree2);
  return inReg;
}

/*
** Generate code that will evaluate expression pExpr just one time
** per prepared statement execution.
**
** If the expression uses functions (that might throw an exception) then
** guard them with an OP_Once opcode to ensure that the code is only executed
** once. If no functions are involved, then factor the code out and put it at
** the end of the prepared statement in the initialization section.
**
** If regDest>0 then the result is always stored in that register and the
** result is not reusable.  If regDest<0 then this routine is free to
** store the value wherever it wants.  The register where the expression
** is stored is returned.  When regDest<0, two identical expressions might
** code to the same register, if they do not contain function calls and hence
** are factored out into the initialization section at the end of the
** prepared statement.
*/
int sqlite3ExprCodeRunJustOnce(
  Parse *pParse,    /* Parsing context */
  Expr *pExpr,      /* The expression to code when the VDBE initializes */
  int regDest       /* Store the value in this register */
){
  ExprList *p;
  assert( ConstFactorOk(pParse) );
  assert( regDest!=0 );
  p = pParse->pConstExpr;
  if( regDest<0 && p ){
    struct ExprList_item *pItem;
    int i;
    for(pItem=p->a, i=p->nExpr; i>0; pItem++, i--){
      if( pItem->fg.reusable
       && sqlite3ExprCompare(0,pItem->pExpr,pExpr,-1)==0
      ){
        return pItem->u.iConstExprReg;
      }
    }
  }
  pExpr = sqlite3ExprDup(pParse->db, pExpr, 0);
  if( pExpr!=0 && ExprHasProperty(pExpr, EP_HasFunc) ){
    Vdbe *v = pParse->pVdbe;
    int addr;
    assert( v );
    addr = sqlite3VdbeAddOp0(v, OP_Once); VdbeCoverage(v);
    pParse->okConstFactor = 0;
    if( !pParse->db->mallocFailed ){
      if( regDest<0 ) regDest = ++pParse->nMem;
      sqlite3ExprCode(pParse, pExpr, regDest);
    }
    pParse->okConstFactor = 1;
    sqlite3ExprDelete(pParse->db, pExpr);
    sqlite3VdbeJumpHere(v, addr);
  }else{
    p = sqlite3ExprListAppend(pParse, p, pExpr);
    if( p ){
       struct ExprList_item *pItem = &p->a[p->nExpr-1];
       pItem->fg.reusable = regDest<0;
       if( regDest<0 ) regDest = ++pParse->nMem;
       pItem->u.iConstExprReg = regDest;
    }
    pParse->pConstExpr = p;
  }
  return regDest;
}

/*
** Make arrangements to invoke OP_Null on a range of registers
** during initialization.
*/
SQLITE_NOINLINE void sqlite3ExprNullRegisterRange(
  Parse *pParse,   /* Parsing context */
  int iReg,        /* First register to set to NULL */
  int nReg         /* Number of sequential registers to NULL out */
){
  u8 okConstFactor = pParse->okConstFactor;
  Expr t;
  memset(&t, 0, sizeof(t));
  t.op = TK_NULLS;
  t.y.nReg = nReg;
  pParse->okConstFactor = 1;
  sqlite3ExprCodeRunJustOnce(pParse, &t, iReg);
  pParse->okConstFactor = okConstFactor;
}

/*
** Generate code to evaluate an expression and store the results
** into a register.  Return the register number where the results
** are stored.
**
** If the register is a temporary register that can be deallocated,
** then write its number into *pReg.  If the result register is not
** a temporary, then set *pReg to zero.
**
** If pExpr is a constant, then this routine might generate this
** code to fill the register in the initialization section of the
** VDBE program, in order to factor it out of the evaluation loop.
*/
int sqlite3ExprCodeTemp(Parse *pParse, Expr *pExpr, int *pReg){
  int r2;
  pExpr = sqlite3ExprSkipCollateAndLikely(pExpr);
  if( ConstFactorOk(pParse)
   && ALWAYS(pExpr!=0)
   && pExpr->op!=TK_REGISTER
   && sqlite3ExprIsConstantNotJoin(pParse, pExpr)
  ){
    *pReg  = 0;
    r2 = sqlite3ExprCodeRunJustOnce(pParse, pExpr, -1);
  }else{
    int r1 = sqlite3GetTempReg(pParse);
    r2 = sqlite3ExprCodeTarget(pParse, pExpr, r1);
    if( r2==r1 ){
      *pReg = r1;
    }else{
      sqlite3ReleaseTempReg(pParse, r1);
      *pReg = 0;
    }
  }
  return r2;
}

/*
** Generate code that will evaluate expression pExpr and store the
** results in register target.  The results are guaranteed to appear
** in register target.
*/
void sqlite3ExprCode(Parse *pParse, Expr *pExpr, int target){
  int inReg;

  assert( pExpr==0 || !ExprHasVVAProperty(pExpr,EP_Immutable) );
  assert( target>0 && target<=pParse->nMem );
  assert( pParse->pVdbe!=0 || pParse->db->mallocFailed );
  if( pParse->pVdbe==0 ) return;
  inReg = sqlite3ExprCodeTarget(pParse, pExpr, target);
  if( inReg!=target ){
    u8 op;
    Expr *pX = sqlite3ExprSkipCollateAndLikely(pExpr);
    testcase( pX!=pExpr );
    if( ALWAYS(pX)
     && (ExprHasProperty(pX,EP_Subquery) || pX->op==TK_REGISTER)
    ){
      op = OP_Copy;
    }else{
      op = OP_SCopy;
    }
    sqlite3VdbeAddOp2(pParse->pVdbe, op, inReg, target);
  }
}

/*
** Make a transient copy of expression pExpr and then code it using
** sqlite3ExprCode().  This routine works just like sqlite3ExprCode()
** except that the input expression is guaranteed to be unchanged.
*/
void sqlite3ExprCodeCopy(Parse *pParse, Expr *pExpr, int target){
  sqlite3 *db = pParse->db;
  pExpr = sqlite3ExprDup(db, pExpr, 0);
  if( !db->mallocFailed ) sqlite3ExprCode(pParse, pExpr, target);
  sqlite3ExprDelete(db, pExpr);
}

/*
** Generate code that will evaluate expression pExpr and store the
** results in register target.  The results are guaranteed to appear
** in register target.  If the expression is constant, then this routine
** might choose to code the expression at initialization time.
*/
void sqlite3ExprCodeFactorable(Parse *pParse, Expr *pExpr, int target){
  if( pParse->okConstFactor && sqlite3ExprIsConstantNotJoin(pParse,pExpr) ){
    sqlite3ExprCodeRunJustOnce(pParse, pExpr, target);
  }else{
    sqlite3ExprCodeCopy(pParse, pExpr, target);
  }
}

/*
** Generate code that pushes the value of every element of the given
** expression list into a sequence of registers beginning at target.
**
** Return the number of elements evaluated.  The number returned will
** usually be pList->nExpr but might be reduced if SQLITE_ECEL_OMITREF
** is defined.
**
** The SQLITE_ECEL_DUP flag prevents the arguments from being
** filled using OP_SCopy.  OP_Copy must be used instead.
**
** The SQLITE_ECEL_FACTOR argument allows constant arguments to be
** factored out into initialization code.
**
** The SQLITE_ECEL_REF flag means that expressions in the list with
** ExprList.a[].u.x.iOrderByCol>0 have already been evaluated and stored
** in registers at srcReg, and so the value can be copied from there.
** If SQLITE_ECEL_OMITREF is also set, then the values with u.x.iOrderByCol>0
** are simply omitted rather than being copied from srcReg.
*/
int sqlite3ExprCodeExprList(
  Parse *pParse,     /* Parsing context */
  ExprList *pList,   /* The expression list to be coded */
  int target,        /* Where to write results */
  int srcReg,        /* Source registers if SQLITE_ECEL_REF */
  u8 flags           /* SQLITE_ECEL_* flags */
){
  struct ExprList_item *pItem;
  int i, j, n;
  u8 copyOp = (flags & SQLITE_ECEL_DUP) ? OP_Copy : OP_SCopy;
  Vdbe *v = pParse->pVdbe;
  assert( pList!=0 );
  assert( target>0 );
  assert( pParse->pVdbe!=0 );  /* Never gets this far otherwise */
  n = pList->nExpr;
  if( !ConstFactorOk(pParse) ) flags &= ~SQLITE_ECEL_FACTOR;
  for(pItem=pList->a, i=0; i<n; i++, pItem++){
    Expr *pExpr = pItem->pExpr;
#ifdef SQLITE_ENABLE_SORTER_REFERENCES
    if( pItem->fg.bSorterRef ){
      i--;
      n--;
    }else
#endif
    if( (flags & SQLITE_ECEL_REF)!=0 && (j = pItem->u.x.iOrderByCol)>0 ){
      if( flags & SQLITE_ECEL_OMITREF ){
        i--;
        n--;
      }else{
        sqlite3VdbeAddOp2(v, copyOp, j+srcReg-1, target+i);
      }
    }else if( (flags & SQLITE_ECEL_FACTOR)!=0
           && sqlite3ExprIsConstantNotJoin(pParse,pExpr)
    ){
      sqlite3ExprCodeRunJustOnce(pParse, pExpr, target+i);
    }else{
      int inReg = sqlite3ExprCodeTarget(pParse, pExpr, target+i);
      if( inReg!=target+i ){
        VdbeOp *pOp;
        if( copyOp==OP_Copy
         && (pOp=sqlite3VdbeGetLastOp(v))->opcode==OP_Copy
         && pOp->p1+pOp->p3+1==inReg
         && pOp->p2+pOp->p3+1==target+i
         && pOp->p5==0  /* The do-not-merge flag must be clear */
        ){
          pOp->p3++;
        }else{
          sqlite3VdbeAddOp2(v, copyOp, inReg, target+i);
        }
      }
    }
  }
  return n;
}

/*
** Generate code for a BETWEEN operator.
**
**    x BETWEEN y AND z
**
** The above is equivalent to
**
**    x>=y AND x<=z
**
** Code it as such, taking care to do the common subexpression
** elimination of x.
**
** The xJumpIf parameter determines details:
**
**    NULL:                   Store the boolean result in reg[dest]
**    sqlite3ExprIfTrue:      Jump to dest if true
**    sqlite3ExprIfFalse:     Jump to dest if false
**
** The jumpIfNull parameter is ignored if xJumpIf is NULL.
*/
static void exprCodeBetween(
  Parse *pParse,    /* Parsing and code generating context */
  Expr *pExpr,      /* The BETWEEN expression */
  int dest,         /* Jump destination or storage location */
  void (*xJump)(Parse*,Expr*,int,int), /* Action to take */
  int jumpIfNull    /* Take the jump if the BETWEEN is NULL */
){
  Expr exprAnd;     /* The AND operator in  x>=y AND x<=z  */
  Expr compLeft;    /* The  x>=y  term */
  Expr compRight;   /* The  x<=z  term */
  int regFree1 = 0; /* Temporary use register */
  Expr *pDel = 0;
  sqlite3 *db = pParse->db;

  memset(&compLeft, 0, sizeof(Expr));
  memset(&compRight, 0, sizeof(Expr));
  memset(&exprAnd, 0, sizeof(Expr));

  assert( ExprUseXList(pExpr) );
  pDel = sqlite3ExprDup(db, pExpr->pLeft, 0);
  if( db->mallocFailed==0 ){
    exprAnd.op = TK_AND;
    exprAnd.pLeft = &compLeft;
    exprAnd.pRight = &compRight;
    compLeft.op = TK_GE;
    compLeft.pLeft = pDel;
    compLeft.pRight = pExpr->x.pList->a[0].pExpr;
    compRight.op = TK_LE;
    compRight.pLeft = pDel;
    compRight.pRight = pExpr->x.pList->a[1].pExpr;
    sqlite3ExprToRegister(pDel, exprCodeVector(pParse, pDel, &regFree1));
    if( xJump ){
      xJump(pParse, &exprAnd, dest, jumpIfNull);
    }else{
      /* Mark the expression is being from the ON or USING clause of a join
      ** so that the sqlite3ExprCodeTarget() routine will not attempt to move
      ** it into the Parse.pConstExpr list.  We should use a new bit for this,
      ** for clarity, but we are out of bits in the Expr.flags field so we
      ** have to reuse the EP_OuterON bit.  Bummer. */
      pDel->flags |= EP_OuterON;
      sqlite3ExprCodeTarget(pParse, &exprAnd, dest);
    }
    sqlite3ReleaseTempReg(pParse, regFree1);
  }
  sqlite3ExprDelete(db, pDel);

  /* Ensure adequate test coverage */
  testcase( xJump==sqlite3ExprIfTrue  && jumpIfNull==0 && regFree1==0 );
  testcase( xJump==sqlite3ExprIfTrue  && jumpIfNull==0 && regFree1!=0 );
  testcase( xJump==sqlite3ExprIfTrue  && jumpIfNull!=0 && regFree1==0 );
  testcase( xJump==sqlite3ExprIfTrue  && jumpIfNull!=0 && regFree1!=0 );
  testcase( xJump==sqlite3ExprIfFalse && jumpIfNull==0 && regFree1==0 );
  testcase( xJump==sqlite3ExprIfFalse && jumpIfNull==0 && regFree1!=0 );
  testcase( xJump==sqlite3ExprIfFalse && jumpIfNull!=0 && regFree1==0 );
  testcase( xJump==sqlite3ExprIfFalse && jumpIfNull!=0 && regFree1!=0 );
  testcase( xJump==0 );
}

/*
** Generate code for a boolean expression such that a jump is made
** to the label "dest" if the expression is true but execution
** continues straight thru if the expression is false.
**
** If the expression evaluates to NULL (neither true nor false), then
** take the jump if the jumpIfNull flag is SQLITE_JUMPIFNULL.
**
** This code depends on the fact that certain token values (ex: TK_EQ)
** are the same as opcode values (ex: OP_Eq) that implement the corresponding
** operation.  Special comments in vdbe.c and the mkopcodeh.awk script in
** the make process cause these values to align.  Assert()s in the code
** below verify that the numbers are aligned correctly.
*/
void sqlite3ExprIfTrue(Parse *pParse, Expr *pExpr, int dest, int jumpIfNull){
  Vdbe *v = pParse->pVdbe;
  int op = 0;
  int regFree1 = 0;
  int regFree2 = 0;
  int r1, r2;

  assert( jumpIfNull==SQLITE_JUMPIFNULL || jumpIfNull==0 );
  if( NEVER(v==0) )     return;  /* Existence of VDBE checked by caller */
  if( NEVER(pExpr==0) ) return;  /* No way this can happen */
  assert( !ExprHasVVAProperty(pExpr, EP_Immutable) );
  op = pExpr->op;
  switch( op ){
    case TK_AND:
    case TK_OR: {
      Expr *pAlt = sqlite3ExprSimplifiedAndOr(pExpr);
      if( pAlt!=pExpr ){
        sqlite3ExprIfTrue(pParse, pAlt, dest, jumpIfNull);
      }else{
        Expr *pFirst, *pSecond;
        if( exprEvalRhsFirst(pExpr) ){
          pFirst = pExpr->pRight;
          pSecond = pExpr->pLeft;
        }else{
          pFirst = pExpr->pLeft;
          pSecond = pExpr->pRight;
        }
        if( op==TK_AND ){
          int d2 = sqlite3VdbeMakeLabel(pParse);
          testcase( jumpIfNull==0 );
          sqlite3ExprIfFalse(pParse, pFirst, d2,
                             jumpIfNull^SQLITE_JUMPIFNULL);
          sqlite3ExprIfTrue(pParse, pSecond, dest, jumpIfNull);
          sqlite3VdbeResolveLabel(v, d2);
        }else{
          testcase( jumpIfNull==0 );
          sqlite3ExprIfTrue(pParse, pFirst, dest, jumpIfNull);
          sqlite3ExprIfTrue(pParse, pSecond, dest, jumpIfNull);
        }
      }
      break;
    }
    case TK_NOT: {
      testcase( jumpIfNull==0 );
      sqlite3ExprIfFalse(pParse, pExpr->pLeft, dest, jumpIfNull);
      break;
    }
    case TK_TRUTH: {
      int isNot;      /* IS NOT TRUE or IS NOT FALSE */
      int isTrue;     /* IS TRUE or IS NOT TRUE */
      testcase( jumpIfNull==0 );
      isNot = pExpr->op2==TK_ISNOT;
      isTrue = sqlite3ExprTruthValue(pExpr->pRight);
      testcase( isTrue && isNot );
      testcase( !isTrue && isNot );
      if( isTrue ^ isNot ){
        sqlite3ExprIfTrue(pParse, pExpr->pLeft, dest,
                          isNot ? SQLITE_JUMPIFNULL : 0);
      }else{
        sqlite3ExprIfFalse(pParse, pExpr->pLeft, dest,
                           isNot ? SQLITE_JUMPIFNULL : 0);
      }
      break;
    }
    case TK_IS:
    case TK_ISNOT:
      testcase( op==TK_IS );
      testcase( op==TK_ISNOT );
      op = (op==TK_IS) ? TK_EQ : TK_NE;
      jumpIfNull = SQLITE_NULLEQ;
      /* no break */ deliberate_fall_through
    case TK_LT:
    case TK_LE:
    case TK_GT:
    case TK_GE:
    case TK_NE:
    case TK_EQ: {
      int addrIsNull;
      if( sqlite3ExprIsVector(pExpr->pLeft) ) goto default_expr;
      if( ExprHasProperty(pExpr, EP_Subquery) && jumpIfNull!=SQLITE_NULLEQ ){
        addrIsNull = exprComputeOperands(pParse, pExpr,
                                   &r1, &r2, &regFree1, &regFree2);
      }else{
        r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree1);
        r2 = sqlite3ExprCodeTemp(pParse, pExpr->pRight, &regFree2);
        addrIsNull = 0;
      }
      codeCompare(pParse, pExpr->pLeft, pExpr->pRight, op,
                  r1, r2, dest, jumpIfNull, ExprHasProperty(pExpr,EP_Commuted));
      assert(TK_LT==OP_Lt); testcase(op==OP_Lt); VdbeCoverageIf(v,op==OP_Lt);
      assert(TK_LE==OP_Le); testcase(op==OP_Le); VdbeCoverageIf(v,op==OP_Le);
      assert(TK_GT==OP_Gt); testcase(op==OP_Gt); VdbeCoverageIf(v,op==OP_Gt);
      assert(TK_GE==OP_Ge); testcase(op==OP_Ge); VdbeCoverageIf(v,op==OP_Ge);
      assert(TK_EQ==OP_Eq); testcase(op==OP_Eq);
      VdbeCoverageIf(v, op==OP_Eq && jumpIfNull==SQLITE_NULLEQ);
      VdbeCoverageIf(v, op==OP_Eq && jumpIfNull!=SQLITE_NULLEQ);
      assert(TK_NE==OP_Ne); testcase(op==OP_Ne);
      VdbeCoverageIf(v, op==OP_Ne && jumpIfNull==SQLITE_NULLEQ);
      VdbeCoverageIf(v, op==OP_Ne && jumpIfNull!=SQLITE_NULLEQ);
      testcase( regFree1==0 );
      testcase( regFree2==0 );
      if( addrIsNull ){
        if( jumpIfNull ){
          sqlite3VdbeChangeP2(v, addrIsNull, dest);
        }else{
          sqlite3VdbeJumpHere(v, addrIsNull);
        }
      }
      break;
    }
    case TK_ISNULL:
    case TK_NOTNULL: {
      assert( TK_ISNULL==OP_IsNull );   testcase( op==TK_ISNULL );
      assert( TK_NOTNULL==OP_NotNull ); testcase( op==TK_NOTNULL );
      r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree1);
      assert( regFree1==0 || regFree1==r1 );
      if( regFree1 ) sqlite3VdbeTypeofColumn(v, r1);
      sqlite3VdbeAddOp2(v, op, r1, dest);
      VdbeCoverageIf(v, op==TK_ISNULL);
      VdbeCoverageIf(v, op==TK_NOTNULL);
      break;
    }
    case TK_BETWEEN: {
      testcase( jumpIfNull==0 );
      exprCodeBetween(pParse, pExpr, dest, sqlite3ExprIfTrue, jumpIfNull);
      break;
    }
#ifndef SQLITE_OMIT_SUBQUERY
    case TK_IN: {
      int destIfFalse = sqlite3VdbeMakeLabel(pParse);
      int destIfNull = jumpIfNull ? dest : destIfFalse;
      sqlite3ExprCodeIN(pParse, pExpr, destIfFalse, destIfNull);
      sqlite3VdbeGoto(v, dest);
      sqlite3VdbeResolveLabel(v, destIfFalse);
      break;
    }
#endif
    default: {
    default_expr:
      if( ExprAlwaysTrue(pExpr) ){
        sqlite3VdbeGoto(v, dest);
      }else if( ExprAlwaysFalse(pExpr) ){
        /* No-op */
      }else{
        r1 = sqlite3ExprCodeTemp(pParse, pExpr, &regFree1);
        sqlite3VdbeAddOp3(v, OP_If, r1, dest, jumpIfNull!=0);
        VdbeCoverage(v);
        testcase( regFree1==0 );
        testcase( jumpIfNull==0 );
      }
      break;
    }
  }
  sqlite3ReleaseTempReg(pParse, regFree1);
  sqlite3ReleaseTempReg(pParse, regFree2); 
}

/*
** Generate code for a boolean expression such that a jump is made
** to the label "dest" if the expression is false but execution
** continues straight thru if the expression is true.
**
** If the expression evaluates to NULL (neither true nor false) then
** jump if jumpIfNull is SQLITE_JUMPIFNULL or fall through if jumpIfNull
** is 0.
*/
void sqlite3ExprIfFalse(Parse *pParse, Expr *pExpr, int dest, int jumpIfNull){
  Vdbe *v = pParse->pVdbe;
  int op = 0;
  int regFree1 = 0;
  int regFree2 = 0;
  int r1, r2;

  assert( jumpIfNull==SQLITE_JUMPIFNULL || jumpIfNull==0 );
  if( NEVER(v==0) ) return; /* Existence of VDBE checked by caller */
  if( pExpr==0 )    return;
  assert( !ExprHasVVAProperty(pExpr,EP_Immutable) );

  /* The value of pExpr->op and op are related as follows:
  **
  **       pExpr->op            op
  **       ---------          ----------
  **       TK_ISNULL          OP_NotNull
  **       TK_NOTNULL         OP_IsNull
  **       TK_NE              OP_Eq
  **       TK_EQ              OP_Ne
  **       TK_GT              OP_Le
  **       TK_LE              OP_Gt
  **       TK_GE              OP_Lt
  **       TK_LT              OP_Ge
  **
  ** For other values of pExpr->op, op is undefined and unused.
  ** The value of TK_ and OP_ constants are arranged such that we
  ** can compute the mapping above using the following expression.
  ** Assert()s verify that the computation is correct.
  */
  op = ((pExpr->op+(TK_ISNULL&1))^1)-(TK_ISNULL&1);

  /* Verify correct alignment of TK_ and OP_ constants
  */
  assert( pExpr->op!=TK_ISNULL || op==OP_NotNull );
  assert( pExpr->op!=TK_NOTNULL || op==OP_IsNull );
  assert( pExpr->op!=TK_NE || op==OP_Eq );
  assert( pExpr->op!=TK_EQ || op==OP_Ne );
  assert( pExpr->op!=TK_LT || op==OP_Ge );
  assert( pExpr->op!=TK_LE || op==OP_Gt );
  assert( pExpr->op!=TK_GT || op==OP_Le );
  assert( pExpr->op!=TK_GE || op==OP_Lt );

  switch( pExpr->op ){
    case TK_AND:
    case TK_OR: {
      Expr *pAlt = sqlite3ExprSimplifiedAndOr(pExpr);
      if( pAlt!=pExpr ){
        sqlite3ExprIfFalse(pParse, pAlt, dest, jumpIfNull);
      }else{
        Expr *pFirst, *pSecond;
        if( exprEvalRhsFirst(pExpr) ){
          pFirst = pExpr->pRight;
          pSecond = pExpr->pLeft;
        }else{
          pFirst = pExpr->pLeft;
          pSecond = pExpr->pRight;
        }
        if( pExpr->op==TK_AND ){
          testcase( jumpIfNull==0 );
          sqlite3ExprIfFalse(pParse, pFirst, dest, jumpIfNull);
          sqlite3ExprIfFalse(pParse, pSecond, dest, jumpIfNull);
        }else{
          int d2 = sqlite3VdbeMakeLabel(pParse);
          testcase( jumpIfNull==0 );
          sqlite3ExprIfTrue(pParse, pFirst, d2,
                            jumpIfNull^SQLITE_JUMPIFNULL);
          sqlite3ExprIfFalse(pParse, pSecond, dest, jumpIfNull);
          sqlite3VdbeResolveLabel(v, d2);
        }
      }
      break;
    }
    case TK_NOT: {
      testcase( jumpIfNull==0 );
      sqlite3ExprIfTrue(pParse, pExpr->pLeft, dest, jumpIfNull);
      break;
    }
    case TK_TRUTH: {
      int isNot;   /* IS NOT TRUE or IS NOT FALSE */
      int isTrue;  /* IS TRUE or IS NOT TRUE */
      testcase( jumpIfNull==0 );
      isNot = pExpr->op2==TK_ISNOT;
      isTrue = sqlite3ExprTruthValue(pExpr->pRight);
      testcase( isTrue && isNot );
      testcase( !isTrue && isNot );
      if( isTrue ^ isNot ){
        /* IS TRUE and IS NOT FALSE */
        sqlite3ExprIfFalse(pParse, pExpr->pLeft, dest,
                           isNot ? 0 : SQLITE_JUMPIFNULL);

      }else{
        /* IS FALSE and IS NOT TRUE */
        sqlite3ExprIfTrue(pParse, pExpr->pLeft, dest,
                          isNot ? 0 : SQLITE_JUMPIFNULL);
      }
      break;
    }
    case TK_IS:
    case TK_ISNOT:
      testcase( pExpr->op==TK_IS );
      testcase( pExpr->op==TK_ISNOT );
      op = (pExpr->op==TK_IS) ? TK_NE : TK_EQ;
      jumpIfNull = SQLITE_NULLEQ;
      /* no break */ deliberate_fall_through
    case TK_LT:
    case TK_LE:
    case TK_GT:
    case TK_GE:
    case TK_NE:
    case TK_EQ: {
      int addrIsNull;
      if( sqlite3ExprIsVector(pExpr->pLeft) ) goto default_expr;
      if( ExprHasProperty(pExpr, EP_Subquery) && jumpIfNull!=SQLITE_NULLEQ ){
        addrIsNull = exprComputeOperands(pParse, pExpr,
                                   &r1, &r2, &regFree1, &regFree2);
      }else{
        r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree1);
        r2 = sqlite3ExprCodeTemp(pParse, pExpr->pRight, &regFree2);
        addrIsNull = 0;
      }
      codeCompare(pParse, pExpr->pLeft, pExpr->pRight, op,
                  r1, r2, dest, jumpIfNull,ExprHasProperty(pExpr,EP_Commuted));
      assert(TK_LT==OP_Lt); testcase(op==OP_Lt); VdbeCoverageIf(v,op==OP_Lt);
      assert(TK_LE==OP_Le); testcase(op==OP_Le); VdbeCoverageIf(v,op==OP_Le);
      assert(TK_GT==OP_Gt); testcase(op==OP_Gt); VdbeCoverageIf(v,op==OP_Gt);
      assert(TK_GE==OP_Ge); testcase(op==OP_Ge); VdbeCoverageIf(v,op==OP_Ge);
      assert(TK_EQ==OP_Eq); testcase(op==OP_Eq);
      VdbeCoverageIf(v, op==OP_Eq && jumpIfNull!=SQLITE_NULLEQ);
      VdbeCoverageIf(v, op==OP_Eq && jumpIfNull==SQLITE_NULLEQ);
      assert(TK_NE==OP_Ne); testcase(op==OP_Ne);
      VdbeCoverageIf(v, op==OP_Ne && jumpIfNull!=SQLITE_NULLEQ);
      VdbeCoverageIf(v, op==OP_Ne && jumpIfNull==SQLITE_NULLEQ);
      testcase( regFree1==0 );
      testcase( regFree2==0 );
      if( addrIsNull ){
        if( jumpIfNull ){
          sqlite3VdbeChangeP2(v, addrIsNull, dest);
        }else{
          sqlite3VdbeJumpHere(v, addrIsNull);
        }
      }
      break;
    }
    case TK_ISNULL:
    case TK_NOTNULL: {
      r1 = sqlite3ExprCodeTemp(pParse, pExpr->pLeft, &regFree1);
      assert( regFree1==0 || regFree1==r1 );
      if( regFree1 ) sqlite3VdbeTypeofColumn(v, r1);
      sqlite3VdbeAddOp2(v, op, r1, dest);
      testcase( op==TK_ISNULL );   VdbeCoverageIf(v, op==TK_ISNULL);
      testcase( op==TK_NOTNULL );  VdbeCoverageIf(v, op==TK_NOTNULL);
      break;
    }
    case TK_BETWEEN: {
      testcase( jumpIfNull==0 );
      exprCodeBetween(pParse, pExpr, dest, sqlite3ExprIfFalse, jumpIfNull);
      break;
    }
#ifndef SQLITE_OMIT_SUBQUERY
    case TK_IN: {
      if( jumpIfNull ){
        sqlite3ExprCodeIN(pParse, pExpr, dest, dest);
      }else{
        int destIfNull = sqlite3VdbeMakeLabel(pParse);
        sqlite3ExprCodeIN(pParse, pExpr, dest, destIfNull);
        sqlite3VdbeResolveLabel(v, destIfNull);
      }
      break;
    }
#endif
    default: {
    default_expr:
      if( ExprAlwaysFalse(pExpr) ){
        sqlite3VdbeGoto(v, dest);
      }else if( ExprAlwaysTrue(pExpr) ){
        /* no-op */
      }else{
        r1 = sqlite3ExprCodeTemp(pParse, pExpr, &regFree1);
        sqlite3VdbeAddOp3(v, OP_IfNot, r1, dest, jumpIfNull!=0);
        VdbeCoverage(v);
        testcase( regFree1==0 );
        testcase( jumpIfNull==0 );
      }
      break;
    }
  }
  sqlite3ReleaseTempReg(pParse, regFree1);
  sqlite3ReleaseTempReg(pParse, regFree2);
}

/*
** Like sqlite3ExprIfFalse() except that a copy is made of pExpr before
** code generation, and that copy is deleted after code generation. This
** ensures that the original pExpr is unchanged.
*/
void sqlite3ExprIfFalseDup(Parse *pParse, Expr *pExpr, int dest,int jumpIfNull){
  sqlite3 *db = pParse->db;
  Expr *pCopy = sqlite3ExprDup(db, pExpr, 0);
  if( db->mallocFailed==0 ){
    sqlite3ExprIfFalse(pParse, pCopy, dest, jumpIfNull);
  }
  sqlite3ExprDelete(db, pCopy);
}

/*
** Expression pVar is guaranteed to be an SQL variable. pExpr may be any
** type of expression.
**
** If pExpr is a simple SQL value - an integer, real, string, blob
** or NULL value - then the VDBE currently being prepared is configured
** to re-prepare each time a new value is bound to variable pVar.
**
** Additionally, if pExpr is a simple SQL value and the value is the
** same as that currently bound to variable pVar, non-zero is returned.
** Otherwise, if the values are not the same or if pExpr is not a simple
** SQL value, zero is returned.
**
** If the SQLITE_EnableQPSG flag is set on the database connection, then
** this routine always returns false.
*/
static SQLITE_NOINLINE int exprCompareVariable(
  const Parse *pParse,
  const Expr *pVar,
  const Expr *pExpr
){
  int res = 2;
  int iVar;
  sqlite3_value *pL, *pR = 0;
 
  if( pExpr->op==TK_VARIABLE && pVar->iColumn==pExpr->iColumn ){
    return 0;
  }
  if( (pParse->db->flags & SQLITE_EnableQPSG)!=0 ) return 2;
  sqlite3ValueFromExpr(pParse->db, pExpr, SQLITE_UTF8, SQLITE_AFF_BLOB, &pR);
  if( pR ){
    iVar = pVar->iColumn;
    sqlite3VdbeSetVarmask(pParse->pVdbe, iVar);
    pL = sqlite3VdbeGetBoundValue(pParse->pReprepare, iVar, SQLITE_AFF_BLOB);
    if( pL ){
      if( sqlite3_value_type(pL)==SQLITE_TEXT ){
        sqlite3_value_text(pL); /* Make sure the encoding is UTF-8 */
      }
      res = sqlite3MemCompare(pL, pR, 0) ? 2 : 0;
    }
    sqlite3ValueFree(pR);
    sqlite3ValueFree(pL);
  }
  return res;
}

/*
** Do a deep comparison of two expression trees.  Return 0 if the two
** expressions are completely identical.  Return 1 if they differ only
** by a COLLATE operator at the top level.  Return 2 if there are differences
** other than the top-level COLLATE operator.
**
** If any subelement of pB has Expr.iTable==(-1) then it is allowed
** to compare equal to an equivalent element in pA with Expr.iTable==iTab.
**
** The pA side might be using TK_REGISTER.  If that is the case and pB is
** not using TK_REGISTER but is otherwise equivalent, then still return 0.
**
** Sometimes this routine will return 2 even if the two expressions
** really are equivalent.  If we cannot prove that the expressions are
** identical, we return 2 just to be safe.  So if this routine
** returns 2, then you do not really know for certain if the two
** expressions are the same.  But if you get a 0 or 1 return, then you
** can be sure the expressions are the same.  In the places where
** this routine is used, it does not hurt to get an extra 2 - that
** just might result in some slightly slower code.  But returning
** an incorrect 0 or 1 could lead to a malfunction.
**
** If pParse is not NULL and SQLITE_EnableQPSG is off then TK_VARIABLE
** terms in pA with bindings in pParse->pReprepare can be matched against
** literals in pB.  The pParse->pVdbe->expmask bitmask is updated for
** each variable referenced.
*/
int sqlite3ExprCompare(
  const Parse *pParse,
  const Expr *pA,
  const Expr *pB,
  int iTab
){
  u32 combinedFlags;
  if( pA==0 || pB==0 ){
    return pB==pA ? 0 : 2;
  }
  if( pParse && pA->op==TK_VARIABLE ){
    return exprCompareVariable(pParse, pA, pB);
  }
  combinedFlags = pA->flags | pB->flags;
  if( combinedFlags & EP_IntValue ){
    if( (pA->flags&pB->flags&EP_IntValue)!=0 && pA->u.iValue==pB->u.iValue ){
      return 0;
    }
    return 2;
  }
  if( pA->op!=pB->op || pA->op==TK_RAISE ){
    if( pA->op==TK_COLLATE && sqlite3ExprCompare(pParse, pA->pLeft,pB,iTab)<2 ){
      return 1;
    }
    if( pB->op==TK_COLLATE && sqlite3ExprCompare(pParse, pA,pB->pLeft,iTab)<2 ){
      return 1;
    }
    if( pA->op==TK_AGG_COLUMN && pB->op==TK_COLUMN
     && pB->iTable<0 && pA->iTable==iTab
    ){
      /* fall through */
    }else{
      return 2;
    }
  }
  assert( !ExprHasProperty(pA, EP_IntValue) );
  assert( !ExprHasProperty(pB, EP_IntValue) );
  if( pA->u.zToken ){
    if( pA->op==TK_FUNCTION || pA->op==TK_AGG_FUNCTION ){
      if( sqlite3StrICmp(pA->u.zToken,pB->u.zToken)!=0 ) return 2;
#ifndef SQLITE_OMIT_WINDOWFUNC
      assert( pA->op==pB->op );
      if( ExprHasProperty(pA,EP_WinFunc)!=ExprHasProperty(pB,EP_WinFunc) ){
        return 2;
      }
      if( ExprHasProperty(pA,EP_WinFunc) ){
        if( sqlite3WindowCompare(pParse, pA->y.pWin, pB->y.pWin, 1)!=0 ){
          return 2;
        }
      }
#endif
    }else if( pA->op==TK_NULL ){
      return 0;
    }else if( pA->op==TK_COLLATE ){
      if( sqlite3_stricmp(pA->u.zToken,pB->u.zToken)!=0 ) return 2;
    }else
    if( pB->u.zToken!=0
     && pA->op!=TK_COLUMN
     && pA->op!=TK_AGG_COLUMN
     && strcmp(pA->u.zToken,pB->u.zToken)!=0
    ){
      return 2;
    }
  }
  if( (pA->flags & (EP_Distinct|EP_Commuted))
     != (pB->flags & (EP_Distinct|EP_Commuted)) ) return 2;
  if( ALWAYS((combinedFlags & EP_TokenOnly)==0) ){
    if( combinedFlags & EP_xIsSelect ) return 2;
    if( (combinedFlags & EP_FixedCol)==0
     && sqlite3ExprCompare(pParse, pA->pLeft, pB->pLeft, iTab) ) return 2;
    if( sqlite3ExprCompare(pParse, pA->pRight, pB->pRight, iTab) ) return 2;
    if( sqlite3ExprListCompare(pA->x.pList, pB->x.pList, iTab) ) return 2;
    if( pA->op!=TK_STRING
     && pA->op!=TK_TRUEFALSE
     && ALWAYS((combinedFlags & EP_Reduced)==0)
    ){
      if( pA->iColumn!=pB->iColumn ) return 2;
      if( pA->op2!=pB->op2 && pA->op==TK_TRUTH ) return 2;
      if( pA->op!=TK_IN && pA->iTable!=pB->iTable && pA->iTable!=iTab ){
        return 2;
      }
    }
  }
  return 0;
}

/*
** Compare two ExprList objects.  Return 0 if they are identical, 1
** if they are certainly different, or 2 if it is not possible to
** determine if they are identical or not.
**
** If any subelement of pB has Expr.iTable==(-1) then it is allowed
** to compare equal to an equivalent element in pA with Expr.iTable==iTab.
**
** This routine might return non-zero for equivalent ExprLists.  The
** only consequence will be disabled optimizations.  But this routine
** must never return 0 if the two ExprList objects are different, or
** a malfunction will result.
**
** Two NULL pointers are considered to be the same.  But a NULL pointer
** always differs from a non-NULL pointer.
*/
int sqlite3ExprListCompare(const ExprList *pA, const ExprList *pB, int iTab){
  int i;
  if( pA==0 && pB==0 ) return 0;
  if( pA==0 || pB==0 ) return 1;
  if( pA->nExpr!=pB->nExpr ) return 1;
  for(i=0; i<pA->nExpr; i++){
    int res;
    Expr *pExprA = pA->a[i].pExpr;
    Expr *pExprB = pB->a[i].pExpr;
    if( pA->a[i].fg.sortFlags!=pB->a[i].fg.sortFlags ) return 1;
    if( (res = sqlite3ExprCompare(0, pExprA, pExprB, iTab)) ) return res;
  }
  return 0;
}

/*
** Like sqlite3ExprCompare() except COLLATE operators at the top-level
** are ignored.
*/
int sqlite3ExprCompareSkip(Expr *pA,Expr *pB, int iTab){
  return sqlite3ExprCompare(0,
             sqlite3ExprSkipCollate(pA),
             sqlite3ExprSkipCollate(pB),
             iTab);
}

/*
** Return non-zero if Expr p can only be true if pNN is not NULL.
**
** Or if seenNot is true, return non-zero if Expr p can only be
** non-NULL if pNN is not NULL
*/
static int exprImpliesNotNull(
  const Parse *pParse,/* Parsing context */
  const Expr *p,      /* The expression to be checked */
  const Expr *pNN,    /* The expression that is NOT NULL */
  int iTab,           /* Table being evaluated */
  int seenNot         /* Return true only if p can be any non-NULL value */
){
  assert( p );
  assert( pNN );
  if( sqlite3ExprCompare(pParse, p, pNN, iTab)==0 ){
    return pNN->op!=TK_NULL;
  }
  switch( p->op ){
    case TK_IN: {
      if( seenNot && ExprHasProperty(p, EP_xIsSelect) ) return 0;
      assert( ExprUseXSelect(p) || (p->x.pList!=0 && p->x.pList->nExpr>0) );
      return exprImpliesNotNull(pParse, p->pLeft, pNN, iTab, 1);
    }
    case TK_BETWEEN: {
      ExprList *pList;
      assert( ExprUseXList(p) );
      pList = p->x.pList;
      assert( pList!=0 );
      assert( pList->nExpr==2 );
      if( seenNot ) return 0;
      if( exprImpliesNotNull(pParse, pList->a[0].pExpr, pNN, iTab, 1)
       || exprImpliesNotNull(pParse, pList->a[1].pExpr, pNN, iTab, 1)
      ){
        return 1;
      }
      return exprImpliesNotNull(pParse, p->pLeft, pNN, iTab, 1);
    }
    case TK_EQ:
    case TK_NE:
    case TK_LT:
    case TK_LE:
    case TK_GT:
    case TK_GE:
    case TK_PLUS:
    case TK_MINUS:
    case TK_BITOR:
    case TK_LSHIFT:
    case TK_RSHIFT:
    case TK_CONCAT:
      seenNot = 1;
      /* no break */ deliberate_fall_through
    case TK_STAR:
    case TK_REM:
    case TK_BITAND:
    case TK_SLASH: {
      if( exprImpliesNotNull(pParse, p->pRight, pNN, iTab, seenNot) ) return 1;
      /* no break */ deliberate_fall_through
    }
    case TK_SPAN:
    case TK_COLLATE:
    case TK_UPLUS:
    case TK_UMINUS: {
      return exprImpliesNotNull(pParse, p->pLeft, pNN, iTab, seenNot);
    }
    case TK_TRUTH: {
      if( seenNot ) return 0;
      if( p->op2!=TK_IS ) return 0;
      return exprImpliesNotNull(pParse, p->pLeft, pNN, iTab, 1);
    }
    case TK_BITNOT:
    case TK_NOT: {
      return exprImpliesNotNull(pParse, p->pLeft, pNN, iTab, 1);
    }
  }
  return 0;
}

/*
** Return true if the boolean value of the expression is always either
** FALSE or NULL.
*/
static int sqlite3ExprIsNotTrue(Expr *pExpr){
  int v;
  if( pExpr->op==TK_NULL ) return 1;
  if( pExpr->op==TK_TRUEFALSE && sqlite3ExprTruthValue(pExpr)==0 ) return 1;
  v = 1;
  if( sqlite3ExprIsInteger(pExpr, &v, 0) && v==0 ) return 1;
  return 0;
}

/*
** Return true if the expression is one of the following:
**
**    CASE WHEN x THEN y END
**    CASE WHEN x THEN y ELSE NULL END
**    CASE WHEN x THEN y ELSE false END
**    iif(x,y)
**    iif(x,y,NULL)
**    iif(x,y,false)
*/
static int sqlite3ExprIsIIF(sqlite3 *db, const Expr *pExpr){
  ExprList *pList;
  if( pExpr->op==TK_FUNCTION ){
    const char *z = pExpr->u.zToken;
    FuncDef *pDef;
    if( (z[0]!='i' && z[0]!='I') ) return 0;
    if( pExpr->x.pList==0 ) return 0;
    pDef = sqlite3FindFunction(db, z, pExpr->x.pList->nExpr, ENC(db), 0);
#ifdef SQLITE_ENABLE_UNKNOWN_SQL_FUNCTION
    if( pDef==0 ) return 0;
#else
    if( NEVER(pDef==0) ) return 0;
#endif
    if( (pDef->funcFlags & SQLITE_FUNC_INLINE)==0 ) return 0;
    if( SQLITE_PTR_TO_INT(pDef->pUserData)!=INLINEFUNC_iif ) return 0;
  }else if( pExpr->op==TK_CASE ){
    if( pExpr->pLeft!=0 ) return 0;
  }else{
    return 0;
  }
  pList = pExpr->x.pList;
  assert( pList!=0 );
  if( pList->nExpr==2 ) return 1;
  if( pList->nExpr==3 && sqlite3ExprIsNotTrue(pList->a[2].pExpr) ) return 1;
  return 0;
}

/*
** Return true if we can prove the pE2 will always be true if pE1 is
** true.  Return false if we cannot complete the proof or if pE2 might
** be false.  Examples:
**
**     pE1: x==5        pE2: x==5             Result: true
**     pE1: x>0         pE2: x==5             Result: false
**     pE1: x=21        pE2: x=21 OR y=43     Result: true
**     pE1: x!=123      pE2: x IS NOT NULL    Result: true
**     pE1: x!=?1       pE2: x IS NOT NULL    Result: true
**     pE1: x IS NULL   pE2: x IS NOT NULL    Result: false
**     pE1: x IS ?2     pE2: x IS NOT NULL    Result: false
**     pE1: iif(x,y)    pE2: x                Result: true
**     PE1: iif(x,y,0)  pE2: x                Result: true
**
** When comparing TK_COLUMN nodes between pE1 and pE2, if pE2 has
** Expr.iTable<0 then assume a table number given by iTab.
**
** If pParse is not NULL, then the values of bound variables in pE1 are
** compared against literal values in pE2 and pParse->pVdbe->expmask is
** modified to record which bound variables are referenced.  If pParse
** is NULL, then false will be returned if pE1 contains any bound variables.
**
** When in doubt, return false.  Returning true might give a performance
** improvement.  Returning false might cause a performance reduction, but
** it will always give the correct answer and is hence always safe.
*/
int sqlite3ExprImpliesExpr(
  const Parse *pParse,
  const Expr *pE1,
  const Expr *pE2,
  int iTab
){
  if( sqlite3ExprCompare(pParse, pE1, pE2, iTab)==0 ){
    return 1;
  }
  if( pE2->op==TK_OR
   && (sqlite3ExprImpliesExpr(pParse, pE1, pE2->pLeft, iTab)
             || sqlite3ExprImpliesExpr(pParse, pE1, pE2->pRight, iTab) )
  ){
    return 1;
  }
  if( pE2->op==TK_NOTNULL
   && exprImpliesNotNull(pParse, pE1, pE2->pLeft, iTab, 0)
  ){
    return 1;
  }
  if( sqlite3ExprIsIIF(pParse->db, pE1) ){
    return sqlite3ExprImpliesExpr(pParse,pE1->x.pList->a[0].pExpr,pE2,iTab);
  }
  return 0;
}

/* This is a helper function to impliesNotNullRow().  In this routine,
** set pWalker->eCode to one only if *both* of the input expressions
** separately have the implies-not-null-row property.
*/
static void bothImplyNotNullRow(Walker *pWalker, Expr *pE1, Expr *pE2){
  if( pWalker->eCode==0 ){
    sqlite3WalkExpr(pWalker, pE1);
    if( pWalker->eCode ){
      pWalker->eCode = 0;
      sqlite3WalkExpr(pWalker, pE2);
    }
  }
}

/*
** This is the Expr node callback for sqlite3ExprImpliesNonNullRow().
** If the expression node requires that the table at pWalker->iCur
** have one or more non-NULL column, then set pWalker->eCode to 1 and abort.
**
** pWalker->mWFlags is non-zero if this inquiry is being undertaking on
** behalf of a RIGHT JOIN (or FULL JOIN).  That makes a difference when
** evaluating terms in the ON clause of an inner join.
**
** This routine controls an optimization.  False positives (setting
** pWalker->eCode to 1 when it should not be) are deadly, but false-negatives
** (never setting pWalker->eCode) is a harmless missed optimization.
*/
static int impliesNotNullRow(Walker *pWalker, Expr *pExpr){
  testcase( pExpr->op==TK_AGG_COLUMN );
  testcase( pExpr->op==TK_AGG_FUNCTION );
  if( ExprHasProperty(pExpr, EP_OuterON) ) return WRC_Prune;
  if( ExprHasProperty(pExpr, EP_InnerON) && pWalker->mWFlags ){
    /* If iCur is used in an inner-join ON clause to the left of a
    ** RIGHT JOIN, that does *not* mean that the table must be non-null.
    ** But it is difficult to check for that condition precisely.
    ** To keep things simple, any use of iCur from any inner-join is
    ** ignored while attempting to simplify a RIGHT JOIN. */
    return WRC_Prune;
  }
  switch( pExpr->op ){
    case TK_ISNOT:
    case TK_ISNULL:
    case TK_NOTNULL:
    case TK_IS:
    case TK_VECTOR:
    case TK_FUNCTION:
    case TK_TRUTH:
    case TK_CASE:
      testcase( pExpr->op==TK_ISNOT );
      testcase( pExpr->op==TK_ISNULL );
      testcase( pExpr->op==TK_NOTNULL );
      testcase( pExpr->op==TK_IS );
      testcase( pExpr->op==TK_VECTOR );
      testcase( pExpr->op==TK_FUNCTION );
      testcase( pExpr->op==TK_TRUTH );
      testcase( pExpr->op==TK_CASE );
      return WRC_Prune;

    case TK_COLUMN:
      if( pWalker->u.iCur==pExpr->iTable ){
        pWalker->eCode = 1;
        return WRC_Abort;
      }
      return WRC_Prune;

    case TK_OR:
    case TK_AND:
      /* Both sides of an AND or OR must separately imply non-null-row.
      ** Consider these cases:
      **    1.  NOT (x AND y)
      **    2.  x OR y
      ** If only one of x or y is non-null-row, then the overall expression
      ** can be true if the other arm is false (case 1) or true (case 2).
      */
      testcase( pExpr->op==TK_OR );
      testcase( pExpr->op==TK_AND );
      bothImplyNotNullRow(pWalker, pExpr->pLeft, pExpr->pRight);
      return WRC_Prune;
       
    case TK_IN:
      /* Beware of "x NOT IN ()" and "x NOT IN (SELECT 1 WHERE false)",
      ** both of which can be true.  But apart from these cases, if
      ** the left-hand side of the IN is NULL then the IN itself will be
      ** NULL. */
      if( ExprUseXList(pExpr) && ALWAYS(pExpr->x.pList->nExpr>0) ){
        sqlite3WalkExpr(pWalker, pExpr->pLeft);
      }
      return WRC_Prune;

    case TK_BETWEEN:
      /* In "x NOT BETWEEN y AND z" either x must be non-null-row or else
      ** both y and z must be non-null row */
      assert( ExprUseXList(pExpr) );
      assert( pExpr->x.pList->nExpr==2 );
      sqlite3WalkExpr(pWalker, pExpr->pLeft);
      bothImplyNotNullRow(pWalker, pExpr->x.pList->a[0].pExpr,
                                   pExpr->x.pList->a[1].pExpr);
      return WRC_Prune;

    /* Virtual tables are allowed to use constraints like x=NULL.  So
    ** a term of the form x=y does not prove that y is not null if x
    ** is the column of a virtual table */
    case TK_EQ:
    case TK_NE:
    case TK_LT:
    case TK_LE:
    case TK_GT:
    case TK_GE: {
      Expr *pLeft = pExpr->pLeft;
      Expr *pRight = pExpr->pRight;
      testcase( pExpr->op==TK_EQ );
      testcase( pExpr->op==TK_NE );
      testcase( pExpr->op==TK_LT );
      testcase( pExpr->op==TK_LE );
      testcase( pExpr->op==TK_GT );
      testcase( pExpr->op==TK_GE );
      /* The y.pTab=0 assignment in wherecode.c always happens after the
      ** impliesNotNullRow() test */
      assert( pLeft->op!=TK_COLUMN || ExprUseYTab(pLeft) );
      assert( pRight->op!=TK_COLUMN || ExprUseYTab(pRight) );
      if( (pLeft->op==TK_COLUMN
           && ALWAYS(pLeft->y.pTab!=0)
           && IsVirtual(pLeft->y.pTab))
       || (pRight->op==TK_COLUMN
           && ALWAYS(pRight->y.pTab!=0)
           && IsVirtual(pRight->y.pTab))
      ){
        return WRC_Prune;
      }
      /* no break */ deliberate_fall_through
    }
    default:
      return WRC_Continue;
  }
}

/*
** Return true (non-zero) if expression p can only be true if at least
** one column of table iTab is non-null.  In other words, return true
** if expression p will always be NULL or false if every column of iTab
** is NULL.
**
** False negatives are acceptable.  In other words, it is ok to return
** zero even if expression p will never be true of every column of iTab
** is NULL.  A false negative is merely a missed optimization opportunity.
**
** False positives are not allowed, however.  A false positive may result
** in an incorrect answer.
**
** Terms of p that are marked with EP_OuterON (and hence that come from
** the ON or USING clauses of OUTER JOINS) are excluded from the analysis.
**
** This routine is used to check if a LEFT JOIN can be converted into
** an ordinary JOIN.  The p argument is the WHERE clause.  If the WHERE
** clause requires that some column of the right table of the LEFT JOIN
** be non-NULL, then the LEFT JOIN can be safely converted into an
** ordinary join.
*/
int sqlite3ExprImpliesNonNullRow(Expr *p, int iTab, int isRJ){
  Walker w;
  p = sqlite3ExprSkipCollateAndLikely(p);
  if( p==0 ) return 0;
  if( p->op==TK_NOTNULL ){
    p = p->pLeft;
  }else{
    while( p->op==TK_AND ){
      if( sqlite3ExprImpliesNonNullRow(p->pLeft, iTab, isRJ) ) return 1;
      p = p->pRight;
    }
  }
  w.xExprCallback = impliesNotNullRow;
  w.xSelectCallback = 0;
  w.xSelectCallback2 = 0;
  w.eCode = 0;
  w.mWFlags = isRJ!=0;
  w.u.iCur = iTab;
  sqlite3WalkExpr(&w, p);
  return w.eCode;
}

/*
** An instance of the following structure is used by the tree walker
** to determine if an expression can be evaluated by reference to the
** index only, without having to do a search for the corresponding
** table entry.  The IdxCover.pIdx field is the index.  IdxCover.iCur
** is the cursor for the table.
*/
struct IdxCover {
  Index *pIdx;     /* The index to be tested for coverage */
  int iCur;        /* Cursor number for the table corresponding to the index */
};

/*
** Check to see if there are references to columns in table
** pWalker->u.pIdxCover->iCur can be satisfied using the index
** pWalker->u.pIdxCover->pIdx.
*/
static int exprIdxCover(Walker *pWalker, Expr *pExpr){
  if( pExpr->op==TK_COLUMN
   && pExpr->iTable==pWalker->u.pIdxCover->iCur
   && sqlite3TableColumnToIndex(pWalker->u.pIdxCover->pIdx, pExpr->iColumn)<0
  ){
    pWalker->eCode = 1;
    return WRC_Abort;
  }
  return WRC_Continue;
}

/*
** Determine if an index pIdx on table with cursor iCur contains will
** the expression pExpr.  Return true if the index does cover the
** expression and false if the pExpr expression references table columns
** that are not found in the index pIdx.
**
** An index covering an expression means that the expression can be
** evaluated using only the index and without having to lookup the
** corresponding table entry.
*/
int sqlite3ExprCoveredByIndex(
  Expr *pExpr,        /* The index to be tested */
  int iCur,           /* The cursor number for the corresponding table */
  Index *pIdx         /* The index that might be used for coverage */
){
  Walker w;
  struct IdxCover xcov;
  memset(&w, 0, sizeof(w));
  xcov.iCur = iCur;
  xcov.pIdx = pIdx;
  w.xExprCallback = exprIdxCover;
  w.u.pIdxCover = &xcov;
  sqlite3WalkExpr(&w, pExpr);
  return !w.eCode;
}


/* Structure used to pass information throughout the Walker in order to
** implement sqlite3ReferencesSrcList().
*/
struct RefSrcList {
  sqlite3 *db;         /* Database connection used for sqlite3DbRealloc() */
  SrcList *pRef;       /* Looking for references to these tables */
  i64 nExclude;        /* Number of tables to exclude from the search */
  int *aiExclude;      /* Cursor IDs for tables to exclude from the search */
};

/*
** Walker SELECT callbacks for sqlite3ReferencesSrcList().
**
** When entering a new subquery on the pExpr argument, add all FROM clause
** entries for that subquery to the exclude list.
**
** When leaving the subquery, remove those entries from the exclude list.
*/
static int selectRefEnter(Walker *pWalker, Select *pSelect){
  struct RefSrcList *p = pWalker->u.pRefSrcList;
  SrcList *pSrc = pSelect->pSrc;
  i64 i, j;
  int *piNew;
  if( pSrc->nSrc==0 ) return WRC_Continue;
  j = p->nExclude;
  p->nExclude += pSrc->nSrc;
  piNew = sqlite3DbRealloc(p->db, p->aiExclude, p->nExclude*sizeof(int));
  if( piNew==0 ){
    p->nExclude = 0;
    return WRC_Abort;
  }else{
    p->aiExclude = piNew;
  }
  for(i=0; i<pSrc->nSrc; i++, j++){
     p->aiExclude[j] = pSrc->a[i].iCursor;
  }
  return WRC_Continue;
}
static void selectRefLeave(Walker *pWalker, Select *pSelect){
  struct RefSrcList *p = pWalker->u.pRefSrcList;
  SrcList *pSrc = pSelect->pSrc;
  if( p->nExclude ){
    assert( p->nExclude>=pSrc->nSrc );
    p->nExclude -= pSrc->nSrc;
  }
}

/* This is the Walker EXPR callback for sqlite3ReferencesSrcList().
**
** Set the 0x01 bit of pWalker->eCode if there is a reference to any
** of the tables shown in RefSrcList.pRef.
**
** Set the 0x02 bit of pWalker->eCode if there is a reference to a
** table is in neither RefSrcList.pRef nor RefSrcList.aiExclude.
*/
static int exprRefToSrcList(Walker *pWalker, Expr *pExpr){
  if( pExpr->op==TK_COLUMN
   || pExpr->op==TK_AGG_COLUMN
  ){
    int i;
    struct RefSrcList *p = pWalker->u.pRefSrcList;
    SrcList *pSrc = p->pRef;
    int nSrc = pSrc ? pSrc->nSrc : 0;
    for(i=0; i<nSrc; i++){
      if( pExpr->iTable==pSrc->a[i].iCursor ){
        pWalker->eCode |= 1;
        return WRC_Continue;
      }
    }
    for(i=0; i<p->nExclude && p->aiExclude[i]!=pExpr->iTable; i++){}
    if( i>=p->nExclude ){
      pWalker->eCode |= 2;
    }
  }
  return WRC_Continue;
}

/*
** Check to see if pExpr references any tables in pSrcList.
** Possible return values:
**
**    1         pExpr does references a table in pSrcList.
**
**    0         pExpr references some table that is not defined in either
**              pSrcList or in subqueries of pExpr itself.
**
**   -1         pExpr only references no tables at all, or it only
**              references tables defined in subqueries of pExpr itself.
**
** As currently used, pExpr is always an aggregate function call.  That
** fact is exploited for efficiency.
*/
int sqlite3ReferencesSrcList(Parse *pParse, Expr *pExpr, SrcList *pSrcList){
  Walker w;
  struct RefSrcList x;
  assert( pParse->db!=0 );
  memset(&w, 0, sizeof(w));
  memset(&x, 0, sizeof(x));
  w.xExprCallback = exprRefToSrcList;
  w.xSelectCallback = selectRefEnter;
  w.xSelectCallback2 = selectRefLeave;
  w.u.pRefSrcList = &x;
  x.db = pParse->db;
  x.pRef = pSrcList;
  assert( pExpr->op==TK_AGG_FUNCTION );
  assert( ExprUseXList(pExpr) );
  sqlite3WalkExprList(&w, pExpr->x.pList);
  if( pExpr->pLeft ){
    assert( pExpr->pLeft->op==TK_ORDER );
    assert( ExprUseXList(pExpr->pLeft) );
    assert( pExpr->pLeft->x.pList!=0 );
    sqlite3WalkExprList(&w, pExpr->pLeft->x.pList);
  }
#ifndef SQLITE_OMIT_WINDOWFUNC
  if( ExprHasProperty(pExpr, EP_WinFunc) ){
    sqlite3WalkExpr(&w, pExpr->y.pWin->pFilter);
  }
#endif
  if( x.aiExclude ) sqlite3DbNNFreeNN(pParse->db, x.aiExclude);
  if( w.eCode & 0x01 ){
    return 1;
  }else if( w.eCode ){
    return 0;
  }else{
    return -1;
  }
}

/*
** This is a Walker expression node callback.
**
** For Expr nodes that contain pAggInfo pointers, make sure the AggInfo
** object that is referenced does not refer directly to the Expr.  If
** it does, make a copy.  This is done because the pExpr argument is
** subject to change.
**
** The copy is scheduled for deletion using the sqlite3ExprDeferredDelete()
** which builds on the sqlite3ParserAddCleanup() mechanism.
*/
static int agginfoPersistExprCb(Walker *pWalker, Expr *pExpr){
  if( ALWAYS(!ExprHasProperty(pExpr, EP_TokenOnly|EP_Reduced))
   && pExpr->pAggInfo!=0
  ){
    AggInfo *pAggInfo = pExpr->pAggInfo;
    int iAgg = pExpr->iAgg;
    Parse *pParse = pWalker->pParse;
    sqlite3 *db = pParse->db;
    assert( iAgg>=0 );
    if( pExpr->op!=TK_AGG_FUNCTION ){
      if( iAgg<pAggInfo->nColumn
       && pAggInfo->aCol[iAgg].pCExpr==pExpr
      ){
        pExpr = sqlite3ExprDup(db, pExpr, 0);
        if( pExpr && !sqlite3ExprDeferredDelete(pParse, pExpr) ){
          pAggInfo->aCol[iAgg].pCExpr = pExpr;
        }
      }
    }else{
      assert( pExpr->op==TK_AGG_FUNCTION );
      if( ALWAYS(iAgg<pAggInfo->nFunc)
       && pAggInfo->aFunc[iAgg].pFExpr==pExpr
      ){
        pExpr = sqlite3ExprDup(db, pExpr, 0);
        if( pExpr && !sqlite3ExprDeferredDelete(pParse, pExpr) ){
          pAggInfo->aFunc[iAgg].pFExpr = pExpr;
        }
      }
    }
  }
  return WRC_Continue;
}

/*
** Initialize a Walker object so that will persist AggInfo entries referenced
** by the tree that is walked.
*/
void sqlite3AggInfoPersistWalkerInit(Walker *pWalker, Parse *pParse){
  memset(pWalker, 0, sizeof(*pWalker));
  pWalker->pParse = pParse;
  pWalker->xExprCallback = agginfoPersistExprCb;
  pWalker->xSelectCallback = sqlite3SelectWalkNoop;
}

/*
** Add a new element to the pAggInfo->aCol[] array.  Return the index of
** the new element.  Return a negative number if malloc fails.
*/
static int addAggInfoColumn(sqlite3 *db, AggInfo *pInfo){
  int i;
  pInfo->aCol = sqlite3ArrayAllocate(
       db,
       pInfo->aCol,
       sizeof(pInfo->aCol[0]),
       &pInfo->nColumn,
       &i
  );
  return i;
}   

/*
** Add a new element to the pAggInfo->aFunc[] array.  Return the index of
** the new element.  Return a negative number if malloc fails.
*/
static int addAggInfoFunc(sqlite3 *db, AggInfo *pInfo){
  int i;
  pInfo->aFunc = sqlite3ArrayAllocate(
       db,
       pInfo->aFunc,
       sizeof(pInfo->aFunc[0]),
       &pInfo->nFunc,
       &i
  );
  return i;
}

/*
** Search the AggInfo object for an aCol[] entry that has iTable and iColumn.
** Return the index in aCol[] of the entry that describes that column.
**
** If no prior entry is found, create a new one and return -1.  The
** new column will have an index of pAggInfo->nColumn-1.
*/
static void findOrCreateAggInfoColumn(
  Parse *pParse,       /* Parsing context */
  AggInfo *pAggInfo,   /* The AggInfo object to search and/or modify */
  Expr *pExpr          /* Expr describing the column to find or insert */
){
  struct AggInfo_col *pCol;
  int k;
  int mxTerm = pParse->db->aLimit[SQLITE_LIMIT_COLUMN];

  assert( mxTerm <= SMXV(i16) );
  assert( pAggInfo->iFirstReg==0 );
  pCol = pAggInfo->aCol;
  for(k=0; k<pAggInfo->nColumn; k++, pCol++){
    if( pCol->pCExpr==pExpr ) return;
    if( pCol->iTable==pExpr->iTable
     && pCol->iColumn==pExpr->iColumn
     && pExpr->op!=TK_IF_NULL_ROW
    ){
      goto fix_up_expr;
    }
  }
  k = addAggInfoColumn(pParse->db, pAggInfo);
  if( k<0 ){
    /* OOM on resize */
    assert( pParse->db->mallocFailed );
    return;
  }
  if( k>mxTerm ){
    sqlite3ErrorMsg(pParse, "more than %d aggregate terms", mxTerm);
    k = mxTerm;
  }
  pCol = &pAggInfo->aCol[k];
  assert( ExprUseYTab(pExpr) );
  pCol->pTab = pExpr->y.pTab;
  pCol->iTable = pExpr->iTable;
  pCol->iColumn = pExpr->iColumn;
  pCol->iSorterColumn = -1;
  pCol->pCExpr = pExpr;
  if( pAggInfo->pGroupBy && pExpr->op!=TK_IF_NULL_ROW ){
    int j, n;
    ExprList *pGB = pAggInfo->pGroupBy;
    struct ExprList_item *pTerm = pGB->a;
    n = pGB->nExpr;
    for(j=0; j<n; j++, pTerm++){
      Expr *pE = pTerm->pExpr;
      if( pE->op==TK_COLUMN
       && pE->iTable==pExpr->iTable
       && pE->iColumn==pExpr->iColumn
      ){
        pCol->iSorterColumn = j;
        break;
      }
    }
  }
  if( pCol->iSorterColumn<0 ){
    pCol->iSorterColumn = pAggInfo->nSortingColumn++;
  }
fix_up_expr:
  ExprSetVVAProperty(pExpr, EP_NoReduce);
  assert( pExpr->pAggInfo==0 || pExpr->pAggInfo==pAggInfo );
  pExpr->pAggInfo = pAggInfo;
  if( pExpr->op==TK_COLUMN ){
    pExpr->op = TK_AGG_COLUMN;
  }
  assert( k <= SMXV(pExpr->iAgg) );
  pExpr->iAgg = (i16)k;
}

/*
** This is the xExprCallback for a tree walker.  It is used to
** implement sqlite3ExprAnalyzeAggregates().  See sqlite3ExprAnalyzeAggregates
** for additional information.
*/
static int analyzeAggregate(Walker *pWalker, Expr *pExpr){
  int i;
  NameContext *pNC = pWalker->u.pNC;
  Parse *pParse = pNC->pParse;
  SrcList *pSrcList = pNC->pSrcList;
  AggInfo *pAggInfo = pNC->uNC.pAggInfo;

  assert( pNC->ncFlags & NC_UAggInfo );
  assert( pAggInfo->iFirstReg==0 );
  switch( pExpr->op ){
    default: {
      IndexedExpr *pIEpr;
      Expr tmp;
      assert( pParse->iSelfTab==0 );
      if( (pNC->ncFlags & NC_InAggFunc)==0 ) break;
      if( pParse->pIdxEpr==0 ) break;
      for(pIEpr=pParse->pIdxEpr; pIEpr; pIEpr=pIEpr->pIENext){
        int iDataCur = pIEpr->iDataCur;
        if( iDataCur<0 ) continue;
        if( sqlite3ExprCompare(0, pExpr, pIEpr->pExpr, iDataCur)==0 ) break;
      }
      if( pIEpr==0 ) break;
      if( NEVER(!ExprUseYTab(pExpr)) ) break;
      for(i=0; i<pSrcList->nSrc; i++){
         if( pSrcList->a[i].iCursor==pIEpr->iDataCur ){
           testcase( i>0 );
           break;
         }
      }
      if( i>=pSrcList->nSrc ) break;
      if( NEVER(pExpr->pAggInfo!=0) ) break; /* Resolved by outer context */
      if( pParse->nErr ){ return WRC_Abort; }

      /* If we reach this point, it means that expression pExpr can be
      ** translated into a reference to an index column as described by
      ** pIEpr.
      */
      memset(&tmp, 0, sizeof(tmp));
      tmp.op = TK_AGG_COLUMN;
      tmp.iTable = pIEpr->iIdxCur;
      tmp.iColumn = pIEpr->iIdxCol;
      findOrCreateAggInfoColumn(pParse, pAggInfo, &tmp);
      if( pParse->nErr ){ return WRC_Abort; }
      assert( pAggInfo->aCol!=0 );
      assert( tmp.iAgg<pAggInfo->nColumn );
      pAggInfo->aCol[tmp.iAgg].pCExpr = pExpr;
      pExpr->pAggInfo = pAggInfo;
      pExpr->iAgg = tmp.iAgg;
      return WRC_Prune;
    }
    case TK_IF_NULL_ROW:
    case TK_AGG_COLUMN:
    case TK_COLUMN: {
      testcase( pExpr->op==TK_AGG_COLUMN );
      testcase( pExpr->op==TK_COLUMN );
      testcase( pExpr->op==TK_IF_NULL_ROW );
      /* Check to see if the column is in one of the tables in the FROM
      ** clause of the aggregate query */
      if( ALWAYS(pSrcList!=0) ){
        SrcItem *pItem = pSrcList->a;
        for(i=0; i<pSrcList->nSrc; i++, pItem++){
          assert( !ExprHasProperty(pExpr, EP_TokenOnly|EP_Reduced) );
          if( pExpr->iTable==pItem->iCursor ){
            findOrCreateAggInfoColumn(pParse, pAggInfo, pExpr);
            break;
          } /* endif pExpr->iTable==pItem->iCursor */
        } /* end loop over pSrcList */
      }
      return WRC_Continue;
    }
    case TK_AGG_FUNCTION: {
      if( (pNC->ncFlags & NC_InAggFunc)==0
       && pWalker->walkerDepth==pExpr->op2
       && pExpr->pAggInfo==0
      ){
        /* Check to see if pExpr is a duplicate of another aggregate
        ** function that is already in the pAggInfo structure
        */
        struct AggInfo_func *pItem = pAggInfo->aFunc;
        int mxTerm = pParse->db->aLimit[SQLITE_LIMIT_COLUMN];
        assert( mxTerm <= SMXV(i16) );
        for(i=0; i<pAggInfo->nFunc; i++, pItem++){
          if( NEVER(pItem->pFExpr==pExpr) ) break;
          if( sqlite3ExprCompare(0, pItem->pFExpr, pExpr, -1)==0 ){
            break;
          }
        }
        if( i>mxTerm ){
          sqlite3ErrorMsg(pParse, "more than %d aggregate terms", mxTerm);
          i = mxTerm;
          assert( i<pAggInfo->nFunc );
        }else if( i>=pAggInfo->nFunc ){
          /* pExpr is original.  Make a new entry in pAggInfo->aFunc[]
          */
          u8 enc = ENC(pParse->db);
          i = addAggInfoFunc(pParse->db, pAggInfo);
          if( i>=0 ){
            int nArg;
            assert( !ExprHasProperty(pExpr, EP_xIsSelect) );
            pItem = &pAggInfo->aFunc[i];
            pItem->pFExpr = pExpr;
            assert( ExprUseUToken(pExpr) );
            nArg = pExpr->x.pList ? pExpr->x.pList->nExpr : 0;
            pItem->pFunc = sqlite3FindFunction(pParse->db,
                                         pExpr->u.zToken, nArg, enc, 0);
            assert( pItem->bOBUnique==0 );
            if( pExpr->pLeft
             && (pItem->pFunc->funcFlags & SQLITE_FUNC_NEEDCOLL)==0
            ){
              /* The NEEDCOLL test above causes any ORDER BY clause on
              ** aggregate min() or max() to be ignored. */
              ExprList *pOBList;
              assert( nArg>0 );
              assert( pExpr->pLeft->op==TK_ORDER );
              assert( ExprUseXList(pExpr->pLeft) );
              pItem->iOBTab = pParse->nTab++;
              pOBList = pExpr->pLeft->x.pList;
              assert( pOBList->nExpr>0 );
              assert( pItem->bOBUnique==0 );
              if( pOBList->nExpr==1
               && nArg==1
               && sqlite3ExprCompare(0,pOBList->a[0].pExpr,
                               pExpr->x.pList->a[0].pExpr,0)==0
              ){
                pItem->bOBPayload = 0;
                pItem->bOBUnique = ExprHasProperty(pExpr, EP_Distinct);
              }else{
                pItem->bOBPayload = 1;
              }
              pItem->bUseSubtype =
                    (pItem->pFunc->funcFlags & SQLITE_SUBTYPE)!=0;
            }else{
              pItem->iOBTab = -1;
            }
            if( ExprHasProperty(pExpr, EP_Distinct) && !pItem->bOBUnique ){
              pItem->iDistinct = pParse->nTab++;
            }else{
              pItem->iDistinct = -1;
            }
          }
        }
        /* Make pExpr point to the appropriate pAggInfo->aFunc[] entry
        */
        assert( !ExprHasProperty(pExpr, EP_TokenOnly|EP_Reduced) );
        ExprSetVVAProperty(pExpr, EP_NoReduce);
        assert( i <= SMXV(pExpr->iAgg) );
        pExpr->iAgg = (i16)i;
        pExpr->pAggInfo = pAggInfo;
        return WRC_Prune;
      }else{
        return WRC_Continue;
      }
    }
  }
  return WRC_Continue;
}

/*
** Analyze the pExpr expression looking for aggregate functions and
** for variables that need to be added to AggInfo object that pNC->pAggInfo
** points to.  Additional entries are made on the AggInfo object as
** necessary.
**
** This routine should only be called after the expression has been
** analyzed by sqlite3ResolveExprNames().
*/
void sqlite3ExprAnalyzeAggregates(NameContext *pNC, Expr *pExpr){
  Walker w;
  w.xExprCallback = analyzeAggregate;
  w.xSelectCallback = sqlite3WalkerDepthIncrease;
  w.xSelectCallback2 = sqlite3WalkerDepthDecrease;
  w.walkerDepth = 0;
  w.u.pNC = pNC;
  w.pParse = 0;
  assert( pNC->pSrcList!=0 );
  sqlite3WalkExpr(&w, pExpr);
}

/*
** Call sqlite3ExprAnalyzeAggregates() for every expression in an
** expression list.  Return the number of errors.
**
** If an error is found, the analysis is cut short.
*/
void sqlite3ExprAnalyzeAggList(NameContext *pNC, ExprList *pList){
  struct ExprList_item *pItem;
  int i;
  if( pList ){
    for(pItem=pList->a, i=0; i<pList->nExpr; i++, pItem++){
      sqlite3ExprAnalyzeAggregates(pNC, pItem->pExpr);
    }
  }
}

/*
** Allocate a single new register for use to hold some intermediate result.
*/
int sqlite3GetTempReg(Parse *pParse){
  if( pParse->nTempReg==0 ){
    return ++pParse->nMem;
  }
  return pParse->aTempReg[--pParse->nTempReg];
}

/*
** Deallocate a register, making available for reuse for some other
** purpose.
*/
void sqlite3ReleaseTempReg(Parse *pParse, int iReg){
  if( iReg ){
    sqlite3VdbeReleaseRegisters(pParse, iReg, 1, 0, 0);
    if( pParse->nTempReg<ArraySize(pParse->aTempReg) ){
      pParse->aTempReg[pParse->nTempReg++] = iReg;
    }
  }
}

/*
** Allocate or deallocate a block of nReg consecutive registers.
*/
int sqlite3GetTempRange(Parse *pParse, int nReg){
  int i, n;
  if( nReg==1 ) return sqlite3GetTempReg(pParse);
  i = pParse->iRangeReg;
  n = pParse->nRangeReg;
  if( nReg<=n ){
    pParse->iRangeReg += nReg;
    pParse->nRangeReg -= nReg;
  }else{
    i = pParse->nMem+1;
    pParse->nMem += nReg;
  }
  return i;
}
void sqlite3ReleaseTempRange(Parse *pParse, int iReg, int nReg){
  if( nReg==1 ){
    sqlite3ReleaseTempReg(pParse, iReg);
    return;
  }
  sqlite3VdbeReleaseRegisters(pParse, iReg, nReg, 0, 0);
  if( nReg>pParse->nRangeReg ){
    pParse->nRangeReg = nReg;
    pParse->iRangeReg = iReg;
  }
}

/*
** Mark all temporary registers as being unavailable for reuse.
**
** Always invoke this procedure after coding a subroutine or co-routine
** that might be invoked from other parts of the code, to ensure that
** the sub/co-routine does not use registers in common with the code that
** invokes the sub/co-routine.
*/
void sqlite3ClearTempRegCache(Parse *pParse){
  pParse->nTempReg = 0;
  pParse->nRangeReg = 0;
}

/*
** Make sure sufficient registers have been allocated so that
** iReg is a valid register number.
*/
void sqlite3TouchRegister(Parse *pParse, int iReg){
  if( pParse->nMem<iReg ) pParse->nMem = iReg;
}

#if defined(SQLITE_ENABLE_STAT4) || defined(SQLITE_DEBUG)
/*
** Return the latest reusable register in the set of all registers.
** The value returned is no less than iMin.  If any register iMin or
** greater is in permanent use, then return one more than that last
** permanent register.
*/
int sqlite3FirstAvailableRegister(Parse *pParse, int iMin){
  const ExprList *pList = pParse->pConstExpr;
  if( pList ){
    int i;
    for(i=0; i<pList->nExpr; i++){
      if( pList->a[i].u.iConstExprReg>=iMin ){
        iMin = pList->a[i].u.iConstExprReg + 1;
      }
    }
  }
  pParse->nTempReg = 0;
  pParse->nRangeReg = 0;
  return iMin;
}
#endif /* SQLITE_ENABLE_STAT4 || SQLITE_DEBUG */

/*
** Validate that no temporary register falls within the range of
** iFirst..iLast, inclusive.  This routine is only call from within assert()
** statements.
*/
#ifdef SQLITE_DEBUG
int sqlite3NoTempsInRange(Parse *pParse, int iFirst, int iLast){
  int i;
  if( pParse->nRangeReg>0
   && pParse->iRangeReg+pParse->nRangeReg > iFirst
   && pParse->iRangeReg <= iLast
  ){
     return 0;
  }
  for(i=0; i<pParse->nTempReg; i++){
    if( pParse->aTempReg[i]>=iFirst && pParse->aTempReg[i]<=iLast ){
      return 0;
    }
  }
  if( pParse->pConstExpr ){
    ExprList *pList = pParse->pConstExpr;
    for(i=0; i<pList->nExpr; i++){
      int iReg = pList->a[i].u.iConstExprReg;
      if( iReg==0 ) continue;
      if( iReg>=iFirst && iReg<=iLast ) return 0;
    }
  }
  return 1;
}
#endif /* SQLITE_DEBUG */