# 2012 November 9 # # 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 for query planning decisions. # # The tests in this file demonstrate the behaviour of the query planner # in determining the order in which joined tables are scanned. # # Assume there are two tables being joined - t1 and t2. Each has a cost # if it is the outer loop, and a cost if it is the inner loop. As follows: # # t1(outer) - cost of scanning t1 as the outer loop. # t1(inner) - cost of scanning t1 as the inner loop. # t2(outer) - cost of scanning t2 as the outer loop. # t2(inner) - cost of scanning t2 as the inner loop. # # Depending on the order in which the planner nests the scans, the total # cost of the join query is one of: # # t1(outer) * t2(inner) # t2(outer) * t1(inner) # # The tests in this file attempt to verify that the planner nests joins in # the correct order when the following are true: # # + (t1(outer) * t2(inner)) > (t1(inner) * t2(outer) # + t1(outer) < t2(outer) # # In other words, when the best overall query plan has t2 as the outer loop, # but when the outer loop is considered independent of the inner, t1 is the # most efficient choice. # # In order to make them more predictable, automatic indexes are turned off for # the tests in this file. # set testdir [file dirname $argv0] source $testdir/tester.tcl set testprefix x do_execsql_test 1.0 { PRAGMA automatic_index = 0; CREATE TABLE t1(a, b, c); CREATE TABLE t2(d, e, f); CREATE UNIQUE INDEX i1 ON t1(a); CREATE UNIQUE INDEX i2 ON t2(d); } {} foreach {tn sql} { 1 "SELECT * FROM t1, t2 WHERE t1.a=t2.e AND t2.d? AND t2.d>t1.c AND t1.b=t2.e" 2 "SELECT * FROM t2, t1 WHERE t1.a>? AND t2.d>t1.c AND t1.b=t2.e" 3 "SELECT * FROM t2 CROSS JOIN t1 WHERE t1.a>? AND t2.d>t1.c AND t1.b=t2.e" } { do_test 2.$tn { db eval "EXPLAIN QUERY PLAN $sql" } {/.*SCAN TABLE t2 .*SEARCH TABLE t1 .*/} } do_execsql_test 3.0 { DROP TABLE t1; DROP TABLE t2; CREATE TABLE t1(a, b, c); CREATE TABLE t2(d, e, f); CREATE UNIQUE INDEX i1 ON t1(a, b); CREATE INDEX i2 ON t2(d); } {} foreach {tn sql} { 1 {SELECT t1.a, t1.b, t2.d, t2.e FROM t1, t2 WHERE t2.d=t1.b AND t1.a=(t2.d+1) AND t1.b = (t2.e+1)} 2 {SELECT t1.a, t1.b, t2.d, t2.e FROM t2, t1 WHERE t2.d=t1.b AND t1.a=(t2.d+1) AND t1.b = (t2.e+1)} 3 {SELECT t1.a, t1.b, t2.d, t2.e FROM t2 CROSS JOIN t1 WHERE t2.d=t1.b AND t1.a=(t2.d+1) AND t1.b = (t2.e+1)} } { do_test 3.$tn { db eval "EXPLAIN QUERY PLAN $sql" } {/.*SCAN TABLE t2 .*SEARCH TABLE t1 .*/} } finish_test