revision-id: 92cccf8708b156f22602f035e0fdc4e3cc893d2f (mariadb-10.0.35-73-g92cccf8) parent(s): 1bda5e3a8f21d14b4af416259f293a92c49daebb author: Igor Babaev committer: Igor Babaev timestamp: 2018-07-24 23:27:28 -0700 message: MDEV-16820 Lost 'Impossible where' from query with inexpensive subquery This patch fixes another problem introduced by the patch for mdev-4817. The latter changed Item_cond::fix_fields() in such a way that it could call the virtual method is_expensive(). With the first its call the method saves the result in Item::is_expensive_cache. For all next calls the method returns the result from this cache. So if the item once was determined as expensive the method always returns true. For subqueries it's not good, because non-optimized subqueries always is considered as expensive. It means that the cache should be invalidated after the call of optimize_constant_subqueries(). --- mysql-test/r/subselect.result | 16 ++++++++++++++++ mysql-test/r/subselect_no_mat.result | 16 ++++++++++++++++ mysql-test/r/subselect_no_opts.result | 16 ++++++++++++++++ mysql-test/r/subselect_no_scache.result | 16 ++++++++++++++++ mysql-test/r/subselect_no_semijoin.result | 16 ++++++++++++++++ mysql-test/t/subselect.test | 15 +++++++++++++++ sql/item.h | 5 +++++ sql/sql_select.cc | 7 +++++++ 8 files changed, 107 insertions(+) diff --git a/mysql-test/r/subselect.result b/mysql-test/r/subselect.result index 79b2810..b074fb3 100644 --- a/mysql-test/r/subselect.result +++ b/mysql-test/r/subselect.result @@ -7211,4 +7211,20 @@ a 5 SET @@optimizer_switch= @optimiser_switch_save; DROP TABLE t1, t2, t3; +# +# MDEV-16820: impossible where with inexpensive subquery +# +create table t1 (a int) engine=myisam; +insert into t1 values (3), (1), (7); +create table t2 (b int, index idx(b)); +insert into t2 values (2), (5), (3), (2); +explain select * from t1 where (select max(b) from t2) = 10; +id select_type table type possible_keys key key_len ref rows Extra +1 PRIMARY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE +2 SUBQUERY NULL NULL NULL NULL NULL NULL NULL Select tables optimized away +explain select * from t1 where (select max(b) from t2) = 10 and t1.a > 3; +id select_type table type possible_keys key key_len ref rows Extra +1 PRIMARY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE +2 SUBQUERY NULL NULL NULL NULL NULL NULL NULL Select tables optimized away +drop table t1,t2; End of 5.5 tests diff --git a/mysql-test/r/subselect_no_mat.result b/mysql-test/r/subselect_no_mat.result index 51c5263..aff68bd 100644 --- a/mysql-test/r/subselect_no_mat.result +++ b/mysql-test/r/subselect_no_mat.result @@ -7204,6 +7204,22 @@ a 5 SET @@optimizer_switch= @optimiser_switch_save; DROP TABLE t1, t2, t3; +# +# MDEV-16820: impossible where with inexpensive subquery +# +create table t1 (a int) engine=myisam; +insert into t1 values (3), (1), (7); +create table t2 (b int, index idx(b)); +insert into t2 values (2), (5), (3), (2); +explain select * from t1 where (select max(b) from t2) = 10; +id select_type table type possible_keys key key_len ref rows Extra +1 PRIMARY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE +2 SUBQUERY NULL NULL NULL NULL NULL NULL NULL Select tables optimized away +explain select * from t1 where (select max(b) from t2) = 10 and t1.a > 3; +id select_type table type possible_keys key key_len ref rows Extra +1 PRIMARY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE +2 SUBQUERY NULL NULL NULL NULL NULL NULL NULL Select tables optimized away +drop table t1,t2; End of 5.5 tests set optimizer_switch=default; select @@optimizer_switch like '%materialization=on%'; diff --git a/mysql-test/r/subselect_no_opts.result b/mysql-test/r/subselect_no_opts.result index 574af7b..f118178 100644 --- a/mysql-test/r/subselect_no_opts.result +++ b/mysql-test/r/subselect_no_opts.result @@ -7202,5 +7202,21 @@ a 5 SET @@optimizer_switch= @optimiser_switch_save; DROP TABLE t1, t2, t3; +# +# MDEV-16820: impossible where with inexpensive subquery +# +create table t1 (a int) engine=myisam; +insert into t1 values (3), (1), (7); +create table t2 (b int, index idx(b)); +insert into t2 values (2), (5), (3), (2); +explain select * from t1 where (select max(b) from t2) = 10; +id select_type table type possible_keys key key_len ref rows Extra +1 PRIMARY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE +2 SUBQUERY NULL NULL NULL NULL NULL NULL NULL Select tables optimized away +explain select * from t1 where (select max(b) from t2) = 10 and t1.a > 3; +id select_type table type possible_keys key key_len ref rows Extra +1 PRIMARY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE +2 SUBQUERY NULL NULL NULL NULL NULL NULL NULL Select tables optimized away +drop table t1,t2; End of 5.5 tests set @optimizer_switch_for_subselect_test=null; diff --git a/mysql-test/r/subselect_no_scache.result b/mysql-test/r/subselect_no_scache.result index 03285cf..6cefce2 100644 --- a/mysql-test/r/subselect_no_scache.result +++ b/mysql-test/r/subselect_no_scache.result @@ -7217,6 +7217,22 @@ a 5 SET @@optimizer_switch= @optimiser_switch_save; DROP TABLE t1, t2, t3; +# +# MDEV-16820: impossible where with inexpensive subquery +# +create table t1 (a int) engine=myisam; +insert into t1 values (3), (1), (7); +create table t2 (b int, index idx(b)); +insert into t2 values (2), (5), (3), (2); +explain select * from t1 where (select max(b) from t2) = 10; +id select_type table type possible_keys key key_len ref rows Extra +1 PRIMARY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE +2 SUBQUERY NULL NULL NULL NULL NULL NULL NULL Select tables optimized away +explain select * from t1 where (select max(b) from t2) = 10 and t1.a > 3; +id select_type table type possible_keys key key_len ref rows Extra +1 PRIMARY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE +2 SUBQUERY NULL NULL NULL NULL NULL NULL NULL Select tables optimized away +drop table t1,t2; End of 5.5 tests set optimizer_switch=default; select @@optimizer_switch like '%subquery_cache=on%'; diff --git a/mysql-test/r/subselect_no_semijoin.result b/mysql-test/r/subselect_no_semijoin.result index 6669c27..884374a 100644 --- a/mysql-test/r/subselect_no_semijoin.result +++ b/mysql-test/r/subselect_no_semijoin.result @@ -7202,6 +7202,22 @@ a 5 SET @@optimizer_switch= @optimiser_switch_save; DROP TABLE t1, t2, t3; +# +# MDEV-16820: impossible where with inexpensive subquery +# +create table t1 (a int) engine=myisam; +insert into t1 values (3), (1), (7); +create table t2 (b int, index idx(b)); +insert into t2 values (2), (5), (3), (2); +explain select * from t1 where (select max(b) from t2) = 10; +id select_type table type possible_keys key key_len ref rows Extra +1 PRIMARY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE +2 SUBQUERY NULL NULL NULL NULL NULL NULL NULL Select tables optimized away +explain select * from t1 where (select max(b) from t2) = 10 and t1.a > 3; +id select_type table type possible_keys key key_len ref rows Extra +1 PRIMARY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE +2 SUBQUERY NULL NULL NULL NULL NULL NULL NULL Select tables optimized away +drop table t1,t2; End of 5.5 tests set @optimizer_switch_for_subselect_test=null; set @join_cache_level_for_subselect_test=NULL; diff --git a/mysql-test/t/subselect.test b/mysql-test/t/subselect.test index 8c9a489..390d363 100644 --- a/mysql-test/t/subselect.test +++ b/mysql-test/t/subselect.test @@ -6096,4 +6096,19 @@ and t1.a in (select `test`.`t3`.`c` from `test`.`t3`); SET @@optimizer_switch= @optimiser_switch_save; DROP TABLE t1, t2, t3; +--echo # +--echo # MDEV-16820: impossible where with inexpensive subquery +--echo # + +create table t1 (a int) engine=myisam; +insert into t1 values (3), (1), (7); + +create table t2 (b int, index idx(b)); +insert into t2 values (2), (5), (3), (2); + +explain select * from t1 where (select max(b) from t2) = 10; +explain select * from t1 where (select max(b) from t2) = 10 and t1.a > 3; + +drop table t1,t2; + --echo End of 5.5 tests diff --git a/sql/item.h b/sql/item.h index b111d74..7c95239 100644 --- a/sql/item.h +++ b/sql/item.h @@ -1275,6 +1275,11 @@ class Item { virtual bool exists2in_processor(uchar *opt_arg) { return 0; } virtual bool find_selective_predicates_list_processor(uchar *opt_arg) { return 0; } + bool cleanup_is_expensive_cache_processor(uchar *arg) + { + is_expensive_cache= (int8)(-1); + return 0; + } /* To call bool function for all arguments */ struct bool_func_call_args diff --git a/sql/sql_select.cc b/sql/sql_select.cc index 43b8d2b..19a727f 100644 --- a/sql/sql_select.cc +++ b/sql/sql_select.cc @@ -1207,6 +1207,13 @@ TODO: make view to decide if it is possible to write to WHERE directly or make S if (optimize_constant_subqueries()) DBUG_RETURN(1); + if (conds && conds->has_subquery()) + (void) conds->walk(&Item::cleanup_is_expensive_cache_processor, + 0, (uchar*)0); + if (having && having->has_subquery()) + (void) having->walk(&Item::cleanup_is_expensive_cache_processor, + 0, (uchar*)0); + if (setup_jtbm_semi_joins(this, join_list, &conds)) DBUG_RETURN(1);