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test/emptytable.test
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drh
Query planner optimization to detect empty tables in a join early and bail out
16 фев 2017, 01:36
16 фев 2017, 01:36
3a3b420
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# 2017-02-15 # # 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. # #*********************************************************************** # # Test cases to show that a join involving an empty table is very fast. # set testdir [file dirname $argv0] source $testdir/tester.tcl # Build some test data # do_execsql_test emptytable-100 { CREATE TABLE t1(a); WITH RECURSIVE c(x) AS (VALUES(1) UNION ALL SELECT x+1 FROM c WHERE x<100) INSERT INTO t1(a) SELECT x FROM c; CREATE TABLE empty(x); SELECT count(*) FROM t1; } {100} # Interrupt queries after 1M cycles to prevent burning excess CPU proc stopDb {args} { db interrupt } db progress 1000000 {stopDb} # Prior to the query planner optimization on 2017-02-15, this query would # take a ridiculous amount of time. If that optimization stops working, # the result here will be in interrupt for running too long. # do_catchsql_test emptytable-110 { SELECT count(*) FROM t1, t1, t1, t1, t1, t1, empty; } {0 0} do_catchsql_test emptytable-120 { SELECT count(*) FROM t1, t1 LEFT JOIN empty; } {0 10000} do_catchsql_test emptytable-121 { SELECT count(*) FROM t1, t1 LEFT JOIN t1, empty; } {0 0} finish_test