revision-id: e1d8522e6529720cb6fea2d533d07871a3c06046 (mariadb-10.1.41-34-ge1d8522e652) parent(s): 0e38cd37c7be46ac2b57344476d68a6dc59bc3a4 author: Varun Gupta committer: Varun Gupta timestamp: 2019-09-11 00:51:20 +0530 message: MDEV-20519: Query plan regression with optimizer_use_condition_selectivity=4 The issue here was that inside the function table_cond_selectivity we were trying to use the ranges estimate for a key for which no sargable condition was present. The fix for this issue is to make reset the quick structures when we read a TABLE structure from the table cache. This would ensure that we don't read some estimate of previous queries --- mysql-test/r/selectivity.result | 56 ++++++++++++++++++++++++++++++++++ mysql-test/r/selectivity_innodb.result | 47 ++++++++++++++++++++++++++++ mysql-test/t/selectivity.test | 32 +++++++++++++++++++ sql/sql_select.cc | 1 + sql/table.cc | 20 ++++++++++++ sql/table.h | 1 + 6 files changed, 157 insertions(+) diff --git a/mysql-test/r/selectivity.result b/mysql-test/r/selectivity.result index 3f5db42d341..db8ff2c53c7 100644 --- a/mysql-test/r/selectivity.result +++ b/mysql-test/r/selectivity.result @@ -1668,4 +1668,60 @@ Note 1003 select `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b` from `test`.`t1` drop table t1; set use_stat_tables= @save_use_stat_tables; set optimizer_use_condition_selectivity=@save_optimizer_use_condition_selectivity; +# +# MDEV-20519: Query plan regression with optimizer_use_condition_selectivity=4 +# +create table t1 (id int, a int, PRIMARY KEY(id), key(a)); +insert into t1 select seq,seq from seq_1_to_100; +create table t2 (id int, a int, b int, PRIMARY KEY(id), key(a), key(b)); +insert into t2 select seq,seq,seq from seq_1_to_100; +set optimizer_switch='exists_to_in=off'; +set optimizer_use_condition_selectivity=2; +SELECT * FROM t1 +WHERE +EXISTS (SELECT * FROM t1 A INNER JOIN t2 ON t2.a = A.id +WHERE A.a=t1.a AND t2.b < 20); +id a +1 1 +2 2 +3 3 +4 4 +5 5 +6 6 +7 7 +8 8 +9 9 +10 10 +11 11 +12 12 +13 13 +14 14 +15 15 +16 16 +17 17 +18 18 +19 19 +explain SELECT * FROM t1 +WHERE +EXISTS (SELECT * FROM t1 A INNER JOIN t2 ON t2.a = A.id +WHERE A.a=t1.a AND t2.b < 20); +id select_type table type possible_keys key key_len ref rows Extra +1 PRIMARY t1 ALL NULL NULL NULL NULL 100 Using where +2 DEPENDENT SUBQUERY A ref PRIMARY,a a 5 test.t1.a 1 +2 DEPENDENT SUBQUERY t2 ref a,b a 5 test.A.id 1 Using where +EXPLAIN SELECT * FROM t1 A, t1 B WHERE A.a = B.a and A.id = 65; +id select_type table type possible_keys key key_len ref rows Extra +1 SIMPLE A const PRIMARY,a PRIMARY 4 const 1 +1 SIMPLE B ref a a 5 const 1 +explain SELECT * FROM t1 +WHERE +EXISTS (SELECT * FROM t1 A INNER JOIN t2 ON t2.a = A.id +WHERE A.a=t1.a AND t2.b < 20); +id select_type table type possible_keys key key_len ref rows Extra +1 PRIMARY t1 ALL NULL NULL NULL NULL 100 Using where +2 DEPENDENT SUBQUERY A ref PRIMARY,a a 5 test.t1.a 1 +2 DEPENDENT SUBQUERY t2 ref a,b a 5 test.A.id 1 Using where +drop table t1,t2; +set optimizer_switch= @save_optimizer_switch; +set optimizer_use_condition_selectivity= @save_optimizer_use_condition_selectivity; # End of 10.1 tests diff --git a/mysql-test/r/selectivity_innodb.result b/mysql-test/r/selectivity_innodb.result index 1d73c2f5d50..f65eddf36ae 100644 --- a/mysql-test/r/selectivity_innodb.result +++ b/mysql-test/r/selectivity_innodb.result @@ -1678,6 +1678,53 @@ Note 1003 select `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b` from `test`.`t1` drop table t1; set use_stat_tables= @save_use_stat_tables; set optimizer_use_condition_selectivity=@save_optimizer_use_condition_selectivity; +# +# MDEV-20519: Query plan regression with optimizer_use_condition_selectivity=4 +# +create table t1 (id int, a int, PRIMARY KEY(id), key(a)); +insert into t1 select seq,seq from seq_1_to_100; +create table t2 (id int, a int, b int, PRIMARY KEY(id), key(a), key(b)); +insert into t2 select seq,seq,seq from seq_1_to_100; +set optimizer_switch='exists_to_in=off'; +set optimizer_use_condition_selectivity=2; +select * from t1 where EXISTS (select * from t1 A INNER JOIN t2 ON t2.a = A.id where A.a=t1.a and t2.b < 20); +id a +1 1 +2 2 +3 3 +4 4 +5 5 +6 6 +7 7 +8 8 +9 9 +10 10 +11 11 +12 12 +13 13 +14 14 +15 15 +16 16 +17 17 +18 18 +19 19 +explain select * from t1 where EXISTS (select * from t1 A INNER JOIN t2 ON t2.a = A.id where A.a=t1.a and t2.b < 20); +id select_type table type possible_keys key key_len ref rows Extra +1 PRIMARY t1 index NULL a 5 NULL 100 Using where; Using index +2 DEPENDENT SUBQUERY A ref PRIMARY,a a 5 test.t1.a 1 Using index +2 DEPENDENT SUBQUERY t2 ref a,b a 5 test.A.id 1 Using where +EXPLAIN SELECT * FROM t1 A, t1 B WHERE A.a = B.a and A.id = 65; +id select_type table type possible_keys key key_len ref rows Extra +1 SIMPLE A const PRIMARY,a PRIMARY 4 const 1 +1 SIMPLE B ref a a 5 const 1 Using index +explain select * from t1 where EXISTS (select * from t1 A INNER JOIN t2 ON t2.a = A.id where A.a=t1.a and t2.b < 20); +id select_type table type possible_keys key key_len ref rows Extra +1 PRIMARY t1 index NULL a 5 NULL 100 Using where; Using index +2 DEPENDENT SUBQUERY A ref PRIMARY,a a 5 test.t1.a 1 Using index +2 DEPENDENT SUBQUERY t2 ref a,b a 5 test.A.id 1 Using where +drop table t1,t2; +set optimizer_switch= @save_optimizer_switch; +set optimizer_use_condition_selectivity= @save_optimizer_use_condition_selectivity; # End of 10.1 tests set optimizer_switch=@save_optimizer_switch_for_selectivity_test; set @tmp_ust= @@use_stat_tables; diff --git a/mysql-test/t/selectivity.test b/mysql-test/t/selectivity.test index f1c9d6b31b8..6f79927e5d6 100644 --- a/mysql-test/t/selectivity.test +++ b/mysql-test/t/selectivity.test @@ -1124,5 +1124,37 @@ drop table t1; set use_stat_tables= @save_use_stat_tables; set optimizer_use_condition_selectivity=@save_optimizer_use_condition_selectivity; + +--echo # +--echo # MDEV-20519: Query plan regression with optimizer_use_condition_selectivity=4 +--echo # + +--source include/have_sequence.inc + +create table t1 (id int, a int, PRIMARY KEY(id), key(a)); +insert into t1 select seq,seq from seq_1_to_100; + +create table t2 (id int, a int, b int, PRIMARY KEY(id), key(a), key(b)); +insert into t2 select seq,seq,seq from seq_1_to_100; + +set optimizer_switch='exists_to_in=off'; +set optimizer_use_condition_selectivity=2; + +let $query= SELECT * FROM t1 + WHERE + EXISTS (SELECT * FROM t1 A INNER JOIN t2 ON t2.a = A.id + WHERE A.a=t1.a AND t2.b < 20); + +eval $query; +eval explain $query; + +EXPLAIN SELECT * FROM t1 A, t1 B WHERE A.a = B.a and A.id = 65; + +eval explain $query; + +drop table t1,t2; +set optimizer_switch= @save_optimizer_switch; +set optimizer_use_condition_selectivity= @save_optimizer_use_condition_selectivity; + --echo # End of 10.1 tests diff --git a/sql/sql_select.cc b/sql/sql_select.cc index 5b96c15bff5..73299b9cdc9 100644 --- a/sql/sql_select.cc +++ b/sql/sql_select.cc @@ -7759,6 +7759,7 @@ double table_cond_selectivity(JOIN *join, uint idx, JOIN_TAB *s, sel*= table_multi_eq_cond_selectivity(join, idx, s, rem_tables, keyparts, ref_keyuse_steps); + DBUG_ASSERT(sel > 0 && sel <= 1); return sel; } diff --git a/sql/table.cc b/sql/table.cc index 94cd174ffd7..ac46ff6a42c 100644 --- a/sql/table.cc +++ b/sql/table.cc @@ -4162,6 +4162,8 @@ void TABLE::init(THD *thd, TABLE_LIST *tl) created= TRUE; cond_selectivity= 1.0; cond_selectivity_sampling_explain= NULL; + quick_condition_rows= 0; + initialize_quick_structures(); #ifdef HAVE_REPLICATION /* used in RBR Triggers */ master_had_triggers= 0; @@ -7546,3 +7548,21 @@ bool fk_modifies_child(enum_fk_option opt) static bool can_write[]= { false, false, true, true, false, true }; return can_write[opt]; } + +/* + @brief + Initialize all the quick structures that are used to stored the + estimates when the range optimizer is run. + @details + This is specifically needed when we read the TABLE structure from the + table cache. There can be some garbage data from previous queries + that need to be reset here. +*/ + +void TABLE::initialize_quick_structures() +{ + bzero(quick_rows, sizeof(quick_rows)); + bzero(quick_key_parts, sizeof(quick_key_parts)); + bzero(quick_costs, sizeof(quick_costs)); + bzero(quick_n_ranges, sizeof(quick_n_ranges)); +} diff --git a/sql/table.h b/sql/table.h index 98ec9f005ea..44803b5aacd 100644 --- a/sql/table.h +++ b/sql/table.h @@ -1450,6 +1450,7 @@ struct TABLE } bool update_const_key_parts(COND *conds); + void initialize_quick_structures(); my_ptrdiff_t default_values_offset() const { return (my_ptrdiff_t) (s->default_values - record[0]); }