vshmidt/pgvector: Open-source vector similarity search for Postgres

src/vector.c
963 строки19 KB
Andrew Kane
Added dimensions check to vector_avg
13 май 2023, 03:19
13 май 2023, 03:195330102
#include "postgres.h"

#include <math.h>

#include "vector.h"
#include "fmgr.h"
#include "catalog/pg_type.h"
#include "lib/stringinfo.h"
#include "libpq/pqformat.h"
#include "utils/array.h"
#include "utils/builtins.h"
#include "utils/lsyscache.h"
#include "utils/numeric.h"

#if PG_VERSION_NUM >= 120000
#include "common/shortest_dec.h"
#include "utils/float.h"
#else
#include <float.h>
#endif

#if PG_VERSION_NUM < 130000
#define TYPALIGN_DOUBLE 'd'
#define TYPALIGN_INT 'i'
#endif

#define STATE_DIMS(x) (ARR_DIMS(x)[0] - 1)
#define CreateStateDatums(dim) palloc(sizeof(Datum) * (dim + 1))

PG_MODULE_MAGIC;

/*
 * Ensure same dimensions
 */
static inline void
CheckDims(Vector * a, Vector * b)
{
	if (a->dim != b->dim)
		ereport(ERROR,
				(errcode(ERRCODE_DATA_EXCEPTION),
				 errmsg("different vector dimensions %d and %d", a->dim, b->dim)));
}

/*
 * Ensure expected dimension
 */
static inline void
CheckExpectedDim(int32 typmod, int dim)
{
	if (typmod != -1 && typmod != dim)
		ereport(ERROR,
				(errcode(ERRCODE_DATA_EXCEPTION),
				 errmsg("expected %d dimensions, not %d", typmod, dim)));
}


static inline void
CheckDim(int dim)
{
	if (dim < 1)
		ereport(ERROR,
				(errcode(ERRCODE_DATA_EXCEPTION),
				 errmsg("vector must have at least 1 dimension")));

	if (dim > VECTOR_MAX_DIM)
		ereport(ERROR,
				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
				 errmsg("vector cannot have more than %d dimensions", VECTOR_MAX_DIM)));
}

/*
 * Ensure finite elements
 */
static inline void
CheckElement(float value)
{
	if (isnan(value))
		ereport(ERROR,
				(errcode(ERRCODE_DATA_EXCEPTION),
				 errmsg("NaN not allowed in vector")));


	if (isinf(value))
		ereport(ERROR,
				(errcode(ERRCODE_DATA_EXCEPTION),
				 errmsg("infinite value not allowed in vector")));
}

/*
 * Check state array
 */
static float8 *
CheckStateArray(ArrayType *statearray, const char *caller)
{
	if (ARR_NDIM(statearray) != 1 ||
		ARR_DIMS(statearray)[0] < 1 ||
		ARR_HASNULL(statearray) ||
		ARR_ELEMTYPE(statearray) != FLOAT8OID)
		elog(ERROR, "%s: expected state array", caller);
	return (float8 *) ARR_DATA_PTR(statearray);
}

#if PG_VERSION_NUM < 120003
static pg_noinline void
float_overflow_error(void)
{
	ereport(ERROR,
			(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
			 errmsg("value out of range: overflow")));
}
#endif

/*
 * Print vector - useful for debugging
 */
void
PrintVector(char *msg, Vector * vector)
{
	StringInfoData buf;
	int			dim = vector->dim;
	int			i;

	initStringInfo(&buf);

	appendStringInfoChar(&buf, '[');
	for (i = 0; i < dim; i++)
	{
		if (i > 0)
			appendStringInfoString(&buf, ",");
		appendStringInfoString(&buf, float8out_internal(vector->x[i]));
	}
	appendStringInfoChar(&buf, ']');

	elog(INFO, "%s = %s", msg, buf.data);
}

/*
 * Convert textual representation to internal representation
 */
PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_in);
Datum
vector_in(PG_FUNCTION_ARGS)
{
	char	   *str = PG_GETARG_CSTRING(0);
	int32		typmod = PG_GETARG_INT32(2);
	int			i;
	float		x[VECTOR_MAX_DIM];
	int			dim = 0;
	char	   *pt;
	char	   *stringEnd;
	Vector	   *result;

	if (*str != '[')
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
				 errmsg("malformed vector literal: \"%s\"", str),
				 errdetail("Vector contents must start with \"[\".")));

	str++;
	pt = strtok(str, ",");
	stringEnd = pt;

	while (pt != NULL && *stringEnd != ']')
	{
		if (dim == VECTOR_MAX_DIM)
			ereport(ERROR,
					(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
					 errmsg("vector cannot have more than %d dimensions", VECTOR_MAX_DIM)));

		/* Use strtof like float4in to avoid a double-rounding problem */
		x[dim] = strtof(pt, &stringEnd);
		CheckElement(x[dim]);
		dim++;

		if (stringEnd == pt)
			ereport(ERROR,
					(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
					 errmsg("invalid input syntax for type vector: \"%s\"", pt)));

		if (*stringEnd != '\0' && *stringEnd != ']')
			ereport(ERROR,
					(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
					 errmsg("invalid input syntax for type vector: \"%s\"", pt)));

		pt = strtok(NULL, ",");
	}

	if (*stringEnd != ']')
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
				 errmsg("malformed vector literal"),
				 errdetail("Unexpected end of input.")));

	if (stringEnd[1] != '\0')
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
				 errmsg("malformed vector literal"),
				 errdetail("Junk after closing right brace.")));

	if (dim < 1)
		ereport(ERROR,
				(errcode(ERRCODE_DATA_EXCEPTION),
				 errmsg("vector must have at least 1 dimension")));

	CheckExpectedDim(typmod, dim);

	result = InitVector(dim);
	for (i = 0; i < dim; i++)
		result->x[i] = x[i];

	PG_RETURN_POINTER(result);
}

/*
 * Convert internal representation to textual representation
 */
PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_out);
Datum
vector_out(PG_FUNCTION_ARGS)
{
	Vector	   *vector = PG_GETARG_VECTOR_P(0);
	int			dim = vector->dim;
	char	   *buf;
	char	   *ptr;
	int			i;
	int			n;

#if PG_VERSION_NUM < 120000
	int			ndig = FLT_DIG + extra_float_digits;

	if (ndig < 1)
		ndig = 1;

#define FLOAT_SHORTEST_DECIMAL_LEN (ndig + 10)
#endif

	/*
	 * Need:
	 *
	 * dim * (FLOAT_SHORTEST_DECIMAL_LEN - 1) bytes for
	 * float_to_shortest_decimal_bufn
	 *
	 * dim - 1 bytes for separator
	 *
	 * 3 bytes for [, ], and \0
	 */
	buf = (char *) palloc(FLOAT_SHORTEST_DECIMAL_LEN * dim + 2);
	ptr = buf;

	*ptr = '[';
	ptr++;
	for (i = 0; i < dim; i++)
	{
		if (i > 0)
		{
			*ptr = ',';
			ptr++;
		}

#if PG_VERSION_NUM >= 120000
		n = float_to_shortest_decimal_bufn(vector->x[i], ptr);
#else
		n = sprintf(ptr, "%.*g", ndig, vector->x[i]);
#endif
		ptr += n;
	}
	*ptr = ']';
	ptr++;
	*ptr = '\0';

	PG_FREE_IF_COPY(vector, 0);
	PG_RETURN_CSTRING(buf);
}

/*
 * Convert type modifier
 */
PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_typmod_in);
Datum
vector_typmod_in(PG_FUNCTION_ARGS)
{
	ArrayType  *ta = PG_GETARG_ARRAYTYPE_P(0);
	int32	   *tl;
	int			n;

	tl = ArrayGetIntegerTypmods(ta, &n);

	if (n != 1)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
				 errmsg("invalid type modifier")));

	if (*tl < 1)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
				 errmsg("dimensions for type vector must be at least 1")));

	if (*tl > VECTOR_MAX_DIM)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
				 errmsg("dimensions for type vector cannot exceed %d", VECTOR_MAX_DIM)));

	PG_RETURN_INT32(*tl);
}

/*
 * Convert external binary representation to internal representation
 */
PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_recv);
Datum
vector_recv(PG_FUNCTION_ARGS)
{
	StringInfo	buf = (StringInfo) PG_GETARG_POINTER(0);
	int32		typmod = PG_GETARG_INT32(2);
	Vector	   *result;
	int16		dim;
	int16		unused;
	int			i;

	dim = pq_getmsgint(buf, sizeof(int16));
	unused = pq_getmsgint(buf, sizeof(int16));

	CheckDim(dim);
	CheckExpectedDim(typmod, dim);

	if (unused != 0)
		ereport(ERROR,
				(errcode(ERRCODE_DATA_EXCEPTION),
				 errmsg("expected unused to be 0, not %d", unused)));

	result = InitVector(dim);
	for (i = 0; i < dim; i++)
		result->x[i] = pq_getmsgfloat4(buf);

	PG_RETURN_POINTER(result);
}

/*
 * Convert internal representation to the external binary representation
 */
PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_send);
Datum
vector_send(PG_FUNCTION_ARGS)
{
	Vector	   *vec = PG_GETARG_VECTOR_P(0);
	StringInfoData buf;
	int			i;

	pq_begintypsend(&buf);
	pq_sendint(&buf, vec->dim, sizeof(int16));
	pq_sendint(&buf, vec->unused, sizeof(int16));
	for (i = 0; i < vec->dim; i++)
		pq_sendfloat4(&buf, vec->x[i]);

	PG_RETURN_BYTEA_P(pq_endtypsend(&buf));
}

/*
 * Convert vector to vector
 */
PGDLLEXPORT PG_FUNCTION_INFO_V1(vector);
Datum
vector(PG_FUNCTION_ARGS)
{
	Vector	   *arg = PG_GETARG_VECTOR_P(0);
	int32		typmod = PG_GETARG_INT32(1);

	CheckExpectedDim(typmod, arg->dim);

	PG_RETURN_POINTER(arg);
}

/*
 * Convert array to vector
 */
PGDLLEXPORT PG_FUNCTION_INFO_V1(array_to_vector);
Datum
array_to_vector(PG_FUNCTION_ARGS)
{
	ArrayType  *array = PG_GETARG_ARRAYTYPE_P(0);
	int32		typmod = PG_GETARG_INT32(1);
	int			i;
	Vector	   *result;
	int16		typlen;
	bool		typbyval;
	char		typalign;
	Datum	   *elemsp;
	bool	   *nullsp;
	int			nelemsp;

	if (ARR_NDIM(array) > 1)
		ereport(ERROR,
				(errcode(ERRCODE_DATA_EXCEPTION),
				 errmsg("array must be 1-D")));

	get_typlenbyvalalign(ARR_ELEMTYPE(array), &typlen, &typbyval, &typalign);
	deconstruct_array(array, ARR_ELEMTYPE(array), typlen, typbyval, typalign, &elemsp, &nullsp, &nelemsp);

	CheckDim(nelemsp);
	CheckExpectedDim(typmod, nelemsp);

	result = InitVector(nelemsp);
	for (i = 0; i < nelemsp; i++)
	{
		if (nullsp[i])
			ereport(ERROR,
					(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
					 errmsg("array must not containing NULLs")));

		if (ARR_ELEMTYPE(array) == INT4OID)
			result->x[i] = DatumGetInt32(elemsp[i]);
		else if (ARR_ELEMTYPE(array) == FLOAT8OID)
			result->x[i] = DatumGetFloat8(elemsp[i]);
		else if (ARR_ELEMTYPE(array) == FLOAT4OID)
			result->x[i] = DatumGetFloat4(elemsp[i]);
		else if (ARR_ELEMTYPE(array) == NUMERICOID)
			result->x[i] = DatumGetFloat4(DirectFunctionCall1(numeric_float4, elemsp[i]));
		else
			ereport(ERROR,
					(errcode(ERRCODE_DATA_EXCEPTION),
					 errmsg("unsupported array type")));

		CheckElement(result->x[i]);
	}

	PG_RETURN_POINTER(result);
}

/*
 * Convert vector to float4[]
 */
PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_to_float4);
Datum
vector_to_float4(PG_FUNCTION_ARGS)
{
	Vector	   *vec = PG_GETARG_VECTOR_P(0);
	Datum	   *d;
	ArrayType  *result;
	int			i;

	d = (Datum *) palloc(sizeof(Datum) * vec->dim);

	for (i = 0; i < vec->dim; i++)
		d[i] = Float4GetDatum(vec->x[i]);

	/* Use TYPALIGN_INT for float4 */
	result = construct_array(d, vec->dim, FLOAT4OID, sizeof(float4), true, TYPALIGN_INT);

	PG_RETURN_POINTER(result);
}

/*
 * Get the L2 distance between vectors
 */
PGDLLEXPORT PG_FUNCTION_INFO_V1(l2_distance);
Datum
l2_distance(PG_FUNCTION_ARGS)
{
	Vector	   *a = PG_GETARG_VECTOR_P(0);
	Vector	   *b = PG_GETARG_VECTOR_P(1);
	float	   *ax = a->x;
	float	   *bx = b->x;
	double		distance = 0.0;
	double		diff;

	CheckDims(a, b);

	/* Auto-vectorized */
	for (int i = 0; i < a->dim; i++)
	{
		diff = ax[i] - bx[i];
		distance += diff * diff;
	}

	PG_RETURN_FLOAT8(sqrt(distance));
}

/*
 * Get the L2 squared distance between vectors
 * This saves a sqrt calculation
 */
PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_l2_squared_distance);
Datum
vector_l2_squared_distance(PG_FUNCTION_ARGS)
{
	Vector	   *a = PG_GETARG_VECTOR_P(0);
	Vector	   *b = PG_GETARG_VECTOR_P(1);
	float	   *ax = a->x;
	float	   *bx = b->x;
	double		distance = 0.0;
	double		diff;

	CheckDims(a, b);

	/* Auto-vectorized */
	for (int i = 0; i < a->dim; i++)
	{
		diff = ax[i] - bx[i];
		distance += diff * diff;
	}

	PG_RETURN_FLOAT8(distance);
}

/*
 * Get the inner product of two vectors
 */
PGDLLEXPORT PG_FUNCTION_INFO_V1(inner_product);
Datum
inner_product(PG_FUNCTION_ARGS)
{
	Vector	   *a = PG_GETARG_VECTOR_P(0);
	Vector	   *b = PG_GETARG_VECTOR_P(1);
	float	   *ax = a->x;
	float	   *bx = b->x;
	double		distance = 0.0;

	CheckDims(a, b);

	/* Auto-vectorized */
	for (int i = 0; i < a->dim; i++)
		distance += ax[i] * bx[i];

	PG_RETURN_FLOAT8(distance);
}

/*
 * Get the negative inner product of two vectors
 */
PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_negative_inner_product);
Datum
vector_negative_inner_product(PG_FUNCTION_ARGS)
{
	Vector	   *a = PG_GETARG_VECTOR_P(0);
	Vector	   *b = PG_GETARG_VECTOR_P(1);
	float	   *ax = a->x;
	float	   *bx = b->x;
	double		distance = 0.0;

	CheckDims(a, b);

	/* Auto-vectorized */
	for (int i = 0; i < a->dim; i++)
		distance += ax[i] * bx[i];

	PG_RETURN_FLOAT8(distance * -1);
}

/*
 * Get the cosine distance between two vectors
 */
PGDLLEXPORT PG_FUNCTION_INFO_V1(cosine_distance);
Datum
cosine_distance(PG_FUNCTION_ARGS)
{
	Vector	   *a = PG_GETARG_VECTOR_P(0);
	Vector	   *b = PG_GETARG_VECTOR_P(1);
	float	   *ax = a->x;
	float	   *bx = b->x;
	double		distance = 0.0;
	double		norma = 0.0;
	double		normb = 0.0;

	CheckDims(a, b);

	/* Auto-vectorized */
	for (int i = 0; i < a->dim; i++)
	{
		distance += ax[i] * bx[i];
		norma += ax[i] * ax[i];
		normb += bx[i] * bx[i];
	}

	/* Use sqrt(a * b) over sqrt(a) * sqrt(b) */
	PG_RETURN_FLOAT8(1 - (distance / sqrt(norma * normb)));
}

/*
 * Get the distance for spherical k-means
 * Currently uses angular distance since needs to satisfy triangle inequality
 * Assumes inputs are unit vectors (skips norm)
 */
PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_spherical_distance);
Datum
vector_spherical_distance(PG_FUNCTION_ARGS)
{
	Vector	   *a = PG_GETARG_VECTOR_P(0);
	Vector	   *b = PG_GETARG_VECTOR_P(1);
	double		distance = 0.0;

	CheckDims(a, b);

	/* Auto-vectorized */
	for (int i = 0; i < a->dim; i++)
		distance += a->x[i] * b->x[i];

	/* Prevent NaN with acos with loss of precision */
	if (distance > 1)
		distance = 1;
	else if (distance < -1)
		distance = -1;

	PG_RETURN_FLOAT8(acos(distance) / M_PI);
}

/*
 * Get the dimensions of a vector
 */
PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_dims);
Datum
vector_dims(PG_FUNCTION_ARGS)
{
	Vector	   *a = PG_GETARG_VECTOR_P(0);

	PG_RETURN_INT32(a->dim);
}

/*
 * Get the L2 norm of a vector
 */
PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_norm);
Datum
vector_norm(PG_FUNCTION_ARGS)
{
	Vector	   *a = PG_GETARG_VECTOR_P(0);
	float	   *ax = a->x;
	double		norm = 0.0;

	/* Auto-vectorized */
	for (int i = 0; i < a->dim; i++)
		norm += ax[i] * ax[i];

	PG_RETURN_FLOAT8(sqrt(norm));
}

/*
 * Add vectors
 */
PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_add);
Datum
vector_add(PG_FUNCTION_ARGS)
{
	Vector	   *a = PG_GETARG_VECTOR_P(0);
	Vector	   *b = PG_GETARG_VECTOR_P(1);
	float	   *ax = a->x;
	float	   *bx = b->x;
	Vector	   *result;
	float	   *rx;

	CheckDims(a, b);

	result = InitVector(a->dim);
	rx = result->x;

	/* Auto-vectorized */
	for (int i = 0, imax = a->dim; i < imax; i++)
		rx[i] = ax[i] + bx[i];

	PG_RETURN_POINTER(result);
}

/*
 * Subtract vectors
 */
PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_sub);
Datum
vector_sub(PG_FUNCTION_ARGS)
{
	Vector	   *a = PG_GETARG_VECTOR_P(0);
	Vector	   *b = PG_GETARG_VECTOR_P(1);
	float	   *ax = a->x;
	float	   *bx = b->x;
	Vector	   *result;
	float	   *rx;

	CheckDims(a, b);

	result = InitVector(a->dim);
	rx = result->x;

	/* Auto-vectorized */
	for (int i = 0, imax = a->dim; i < imax; i++)
		rx[i] = ax[i] - bx[i];

	PG_RETURN_POINTER(result);
}

/*
 * Internal helper to compare vectors
 */
int
vector_cmp_internal(Vector * a, Vector * b)
{
	int			i;

	CheckDims(a, b);

	for (i = 0; i < a->dim; i++)
	{
		if (a->x[i] < b->x[i])
			return -1;

		if (a->x[i] > b->x[i])
			return 1;
	}
	return 0;
}

/*
 * Less than
 */
PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_lt);
Datum
vector_lt(PG_FUNCTION_ARGS)
{
	Vector	   *a = (Vector *) PG_GETARG_VECTOR_P(0);
	Vector	   *b = (Vector *) PG_GETARG_VECTOR_P(1);

	PG_RETURN_BOOL(vector_cmp_internal(a, b) < 0);
}

/*
 * Less than or equal
 */
PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_le);
Datum
vector_le(PG_FUNCTION_ARGS)
{
	Vector	   *a = (Vector *) PG_GETARG_VECTOR_P(0);
	Vector	   *b = (Vector *) PG_GETARG_VECTOR_P(1);

	PG_RETURN_BOOL(vector_cmp_internal(a, b) <= 0);
}

/*
 * Equal
 */
PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_eq);
Datum
vector_eq(PG_FUNCTION_ARGS)
{
	Vector	   *a = (Vector *) PG_GETARG_VECTOR_P(0);
	Vector	   *b = (Vector *) PG_GETARG_VECTOR_P(1);

	PG_RETURN_BOOL(vector_cmp_internal(a, b) == 0);
}

/*
 * Not equal
 */
PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_ne);
Datum
vector_ne(PG_FUNCTION_ARGS)
{
	Vector	   *a = (Vector *) PG_GETARG_VECTOR_P(0);
	Vector	   *b = (Vector *) PG_GETARG_VECTOR_P(1);

	PG_RETURN_BOOL(vector_cmp_internal(a, b) != 0);
}

/*
 * Greater than or equal
 */
PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_ge);
Datum
vector_ge(PG_FUNCTION_ARGS)
{
	Vector	   *a = (Vector *) PG_GETARG_VECTOR_P(0);
	Vector	   *b = (Vector *) PG_GETARG_VECTOR_P(1);

	PG_RETURN_BOOL(vector_cmp_internal(a, b) >= 0);
}

/*
 * Greater than
 */
PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_gt);
Datum
vector_gt(PG_FUNCTION_ARGS)
{
	Vector	   *a = (Vector *) PG_GETARG_VECTOR_P(0);
	Vector	   *b = (Vector *) PG_GETARG_VECTOR_P(1);

	PG_RETURN_BOOL(vector_cmp_internal(a, b) > 0);
}

/*
 * Compare vectors
 */
PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_cmp);
Datum
vector_cmp(PG_FUNCTION_ARGS)
{
	Vector	   *a = (Vector *) PG_GETARG_VECTOR_P(0);
	Vector	   *b = (Vector *) PG_GETARG_VECTOR_P(1);

	PG_RETURN_INT32(vector_cmp_internal(a, b));
}

/*
 * Accumulate vectors
 */
PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_accum);
Datum
vector_accum(PG_FUNCTION_ARGS)
{
	ArrayType  *statearray = PG_GETARG_ARRAYTYPE_P(0);
	Vector	   *newval = PG_GETARG_VECTOR_P(1);
	float8	   *statevalues;
	int16		dim;
	bool		newarr;
	float8		n;
	Datum	   *statedatums;
	float	   *x = newval->x;
	ArrayType  *result;

	/* Check array before using */
	statevalues = CheckStateArray(statearray, "vector_accum");
	dim = STATE_DIMS(statearray);
	newarr = dim == 0;

	if (newarr)
		dim = newval->dim;
	else
		CheckExpectedDim(dim, newval->dim);

	n = statevalues[0] + 1.0;

	statedatums = CreateStateDatums(dim);
	statedatums[0] = Float8GetDatumFast(n);

	if (newarr)
	{
		for (int i = 0; i < dim; i++)
			statedatums[i + 1] = Float8GetDatumFast((double) x[i]);
	}
	else
	{
		for (int i = 0; i < dim; i++)
		{
			double		v = statevalues[i + 1] + x[i];

			if (isinf(v))
				float_overflow_error();

			statedatums[i + 1] = Float8GetDatumFast(v);
		}
	}

	/* Use float8 array like float4_accum */
	result = construct_array(statedatums, dim + 1,
							 FLOAT8OID,
							 sizeof(float8), FLOAT8PASSBYVAL, TYPALIGN_DOUBLE);

	pfree(statedatums);

	PG_RETURN_ARRAYTYPE_P(result);
}

/*
 * Combine vectors
 */
PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_combine);
Datum
vector_combine(PG_FUNCTION_ARGS)
{
	ArrayType  *statearray1 = PG_GETARG_ARRAYTYPE_P(0);
	ArrayType  *statearray2 = PG_GETARG_ARRAYTYPE_P(1);
	float8	   *statevalues1;
	float8	   *statevalues2;
	float8		n;
	float8		n1;
	float8		n2;
	int16		dim;
	Datum	   *statedatums;
	ArrayType  *result;

	/* Check arrays before using */
	statevalues1 = CheckStateArray(statearray1, "vector_combine");
	statevalues2 = CheckStateArray(statearray2, "vector_combine");

	n1 = statevalues1[0];
	n2 = statevalues2[0];

	if (n1 == 0.0)
	{
		n = n2;
		dim = STATE_DIMS(statearray2);
		statedatums = CreateStateDatums(dim);
		for (int i = 1; i <= dim; i++)
			statedatums[i] = Float8GetDatumFast(statevalues2[i]);
	}
	else if (n2 == 0.0)
	{
		n = n1;
		dim = STATE_DIMS(statearray1);
		statedatums = CreateStateDatums(dim);
		for (int i = 1; i <= dim; i++)
			statedatums[i] = Float8GetDatumFast(statevalues1[i]);
	}
	else
	{
		n = n1 + n2;
		dim = STATE_DIMS(statearray1);
		CheckExpectedDim(dim, STATE_DIMS(statearray2));
		statedatums = CreateStateDatums(dim);
		for (int i = 1; i <= dim; i++)
		{
			double		v = statevalues1[i] + statevalues2[i];

			if (isinf(v))
				float_overflow_error();

			statedatums[i] = Float8GetDatumFast(v);
		}
	}

	statedatums[0] = Float8GetDatumFast(n);

	result = construct_array(statedatums, dim + 1,
							 FLOAT8OID,
							 sizeof(float8), FLOAT8PASSBYVAL, TYPALIGN_DOUBLE);

	pfree(statedatums);

	PG_RETURN_ARRAYTYPE_P(result);
}

/*
 * Average vectors
 */
PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_avg);
Datum
vector_avg(PG_FUNCTION_ARGS)
{
	ArrayType  *statearray = PG_GETARG_ARRAYTYPE_P(0);
	float8	   *statevalues;
	float8		n;
	uint16		dim;
	Vector	   *result;
	float		v;

	/* Check array before using */
	statevalues = CheckStateArray(statearray, "vector_avg");
	n = statevalues[0];

	/* SQL defines AVG of no values to be NULL */
	if (n == 0.0)
		PG_RETURN_NULL();

	/* Create vector */
	dim = STATE_DIMS(statearray);
	CheckDim(dim);
	result = InitVector(dim);
	for (int i = 0; i < dim; i++)
	{
		v = statevalues[i + 1] / n;
		CheckElement(v);
		result->x[i] = v;
	}

	PG_RETURN_POINTER(result);
}