From 353b6f26b1469f4d77d2eedee9653207503377ed Mon Sep 17 00:00:00 2001 From: unknown Date: Fri, 4 May 2007 16:43:29 +0300 Subject: [PATCH] Bug #27531: the 4.1 fix. When checking for applicability of join cache we must disable its usage only if there is no temp table in use. When a temp table is used we can use join cache (and it will not make the result-set unordered) to fill the temp table. The filesort() operation is then applied to the data in the temp table and hence is not affected by join cache usage. Fixed by narrowing the condition for disabling join cache to exclude the case where temp table is used. mysql-test/r/join.result: Bug #27531: test case mysql-test/t/join.test: Bug #27531: test case sql/sql_select.cc: Bug #27531: Disable join cache only if not using temp table --- mysql-test/r/join.result | 50 ++++++++++++++++++++++++++++++++++++++++ mysql-test/t/join.test | 24 +++++++++++++++++++ sql/sql_select.cc | 9 +++++--- 3 files changed, 80 insertions(+), 3 deletions(-) diff --git a/mysql-test/r/join.result b/mysql-test/r/join.result index dc763472b0e..9ac8825fcb8 100644 --- a/mysql-test/r/join.result +++ b/mysql-test/r/join.result @@ -376,3 +376,53 @@ i i i 2 NULL 4 2 2 2 drop table t1,t2,t3; +CREATE TABLE t1 (a int, b int default 0, c int default 1); +INSERT INTO t1 (a) VALUES (1),(2),(3),(4),(5),(6),(7),(8); +INSERT INTO t1 (a) SELECT a + 8 FROM t1; +INSERT INTO t1 (a) SELECT a + 16 FROM t1; +CREATE TABLE t2 (a int, d int, e int default 0); +INSERT INTO t2 (a, d) VALUES (1,1),(2,2),(3,3),(4,4); +INSERT INTO t2 (a, d) SELECT a+4, a+4 FROM t2; +INSERT INTO t2 (a, d) SELECT a+8, a+8 FROM t2; +EXPLAIN +SELECT STRAIGHT_JOIN t2.e FROM t1,t2 WHERE t2.d=1 AND t1.b=t2.e +ORDER BY t1.b, t1.c; +id select_type table type possible_keys key key_len ref rows Extra +1 SIMPLE t1 ALL NULL NULL NULL NULL 32 Using temporary; Using filesort +1 SIMPLE t2 ALL NULL NULL NULL NULL 16 Using where +SELECT STRAIGHT_JOIN t2.e FROM t1,t2 WHERE t2.d=1 AND t1.b=t2.e +ORDER BY t1.b, t1.c; +e +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +0 +DROP TABLE t1,t2; diff --git a/mysql-test/t/join.test b/mysql-test/t/join.test index 2715f30b6cf..0fe5de8c9b7 100644 --- a/mysql-test/t/join.test +++ b/mysql-test/t/join.test @@ -326,4 +326,28 @@ select t1.i,t2.i,t3.i from t2 natural right join t3,t1 order by t1.i,t2.i,t3.i; select t1.i,t2.i,t3.i from t2 right join t3 on (t2.i=t3.i),t1 order by t1.i,t2.i,t3.i; drop table t1,t2,t3; +# +# Bug #27531: Query performance degredation in 4.1.22 and greater +# +CREATE TABLE t1 (a int, b int default 0, c int default 1); + +INSERT INTO t1 (a) VALUES (1),(2),(3),(4),(5),(6),(7),(8); +INSERT INTO t1 (a) SELECT a + 8 FROM t1; +INSERT INTO t1 (a) SELECT a + 16 FROM t1; + +CREATE TABLE t2 (a int, d int, e int default 0); + +INSERT INTO t2 (a, d) VALUES (1,1),(2,2),(3,3),(4,4); +INSERT INTO t2 (a, d) SELECT a+4, a+4 FROM t2; +INSERT INTO t2 (a, d) SELECT a+8, a+8 FROM t2; + +# should use join cache +EXPLAIN +SELECT STRAIGHT_JOIN t2.e FROM t1,t2 WHERE t2.d=1 AND t1.b=t2.e + ORDER BY t1.b, t1.c; +SELECT STRAIGHT_JOIN t2.e FROM t1,t2 WHERE t2.d=1 AND t1.b=t2.e + ORDER BY t1.b, t1.c; + +DROP TABLE t1,t2; + # End of 4.1 tests diff --git a/sql/sql_select.cc b/sql/sql_select.cc index 36a15841065..656d1b5639a 100644 --- a/sql/sql_select.cc +++ b/sql/sql_select.cc @@ -3939,14 +3939,17 @@ make_join_readinfo(JOIN *join, uint options) disable join cache because it will change the ordering of the results. Code handles sort table that is at any location (not only first after the const tables) despite the fact that it's currently prohibited. + We must disable join cache if the first non-const table alone is + ordered. If there is a temp table the ordering is done as a last + operation and doesn't prevent join cache usage. */ - if (!ordered_set && - (table == join->sort_by_table && + if (!ordered_set && !join->need_tmp && + ((table == join->sort_by_table && (!join->order || join->skip_sort_order || test_if_skip_sort_order(tab, join->order, join->select_limit, 1)) ) || - (join->sort_by_table == (TABLE *) 1 && i != join->const_tables)) + (join->sort_by_table == (TABLE *) 1 && i != join->const_tables))) ordered_set= 1; switch (tab->type) {