diff --git a/mysql-test/main/derived_cond_pushdown.result b/mysql-test/main/derived_cond_pushdown.result index 7644e65a868..52d8ccd1b80 100644 --- a/mysql-test/main/derived_cond_pushdown.result +++ b/mysql-test/main/derived_cond_pushdown.result @@ -16703,7 +16703,7 @@ EXPLAIN EXTENDED SELECT * FROM v1 JOIN v2 ON v1.f = v2.f; id select_type table type possible_keys key key_len ref rows filtered Extra 1 PRIMARY NULL NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables -3 LATERAL DERIVED NULL NULL NULL NULL NULL NULL NULL NULL no matching row in const table +3 DERIVED NULL NULL NULL NULL NULL NULL NULL NULL no matching row in const table Warnings: Note 1003 /* select#1 */ select NULL AS `f`,`v2`.`f` AS `f` from `test`.`t1` `a` straight_join `test`.`t1` `b` join `test`.`v2` where 0 DROP VIEW v1,v2; diff --git a/mysql-test/main/derived_split_innodb.result b/mysql-test/main/derived_split_innodb.result index ff71b7df097..6119145105b 100644 --- a/mysql-test/main/derived_split_innodb.result +++ b/mysql-test/main/derived_split_innodb.result @@ -175,3 +175,64 @@ id select_type table type possible_keys key key_len ref rows Extra 3 LATERAL DERIVED t1 ref a,a_2 a 5 test.t1.a 1 Using where; Using temporary; Using filesort 3 LATERAL DERIVED t2 ref c c 5 test.t1.b 1 Using index DROP TABLE t1, t2; +# +# Bug mdev-25714: usage non-splitting covering index is cheaper than +# usage of the best splitting index for one group +# +create table t1 ( +id int not null, itemid int not null, index idx (itemid) +) engine=innodb; +insert into t1 values (1, 2), (2,2), (4,2), (4,2), (0,3), (3,3); +create table t2 (id int not null) engine=innodb; +insert into t2 values (2); +create table t3 ( +id int not null, itemid int not null, userid int not null, primary key (id), +index idx1 (userid, itemid), index idx2 (itemid) +) engine innodb; +insert into t3 values (1,1,1), (2,1,1), (3,2,1), (4,2,1), (5,3,1); +analyze table t1,t2,t3; +Table Op Msg_type Msg_text +test.t1 analyze status OK +test.t2 analyze status OK +test.t3 analyze status OK +set optimizer_switch='split_materialized=on'; +explain select t1.id, t1.itemid, dt.id, t2.id +from t1, +(select itemid, max(id) as id from t3 where userid = 1 group by itemid) dt, +t2 +where t1.id = dt.id and t1.itemid = dt.itemid and t2.id=t1.itemid; +id select_type table type possible_keys key key_len ref rows Extra +1 PRIMARY t2 ALL NULL NULL NULL NULL 1 +1 PRIMARY t1 ref idx idx 4 test.t2.id 1 +1 PRIMARY ref key0 key0 9 test.t2.id,test.t1.id 2 +2 DERIVED t3 ref idx1,idx2 idx1 4 const 5 Using where; Using index +select t1.id, t1.itemid, dt.id, t2.id +from t1, +(select itemid, max(id) as id from t3 where userid = 1 group by itemid) dt, +t2 +where t1.id = dt.id and t1.itemid = dt.itemid and t2.id=t1.itemid; +id itemid id id +4 2 4 2 +4 2 4 2 +set optimizer_switch='split_materialized=off'; +explain select t1.id, t1.itemid, dt.id, t2.id +from t1, +(select itemid, max(id) as id from t3 where userid = 1 group by itemid) dt, +t2 +where t1.id = dt.id and t1.itemid = dt.itemid and t2.id=t1.itemid; +id select_type table type possible_keys key key_len ref rows Extra +1 PRIMARY t2 ALL NULL NULL NULL NULL 1 +1 PRIMARY t1 ref idx idx 4 test.t2.id 1 +1 PRIMARY ref key0 key0 9 test.t2.id,test.t1.id 2 +2 DERIVED t3 ref idx1 idx1 4 const 5 Using where; Using index +select t1.id, t1.itemid, dt.id, t2.id +from t1, +(select itemid, max(id) as id from t3 where userid = 1 group by itemid) dt, +t2 +where t1.id = dt.id and t1.itemid = dt.itemid and t2.id=t1.itemid; +id itemid id id +4 2 4 2 +4 2 4 2 +drop table t1,t2,t3; +set optimizer_switch='split_materialized=default'; +# End of 10.3 tests diff --git a/mysql-test/main/derived_split_innodb.test b/mysql-test/main/derived_split_innodb.test index 19a6ecf216f..6f33c71eede 100644 --- a/mysql-test/main/derived_split_innodb.test +++ b/mysql-test/main/derived_split_innodb.test @@ -150,3 +150,40 @@ eval set statement optimizer_switch='split_materialized=on' for $query; DROP TABLE t1, t2; +--echo # +--echo # Bug mdev-25714: usage non-splitting covering index is cheaper than +--echo # usage of the best splitting index for one group +--echo # + +create table t1 ( + id int not null, itemid int not null, index idx (itemid) +) engine=innodb; +insert into t1 values (1, 2), (2,2), (4,2), (4,2), (0,3), (3,3); +create table t2 (id int not null) engine=innodb; +insert into t2 values (2); +create table t3 ( + id int not null, itemid int not null, userid int not null, primary key (id), + index idx1 (userid, itemid), index idx2 (itemid) +) engine innodb; +insert into t3 values (1,1,1), (2,1,1), (3,2,1), (4,2,1), (5,3,1); +analyze table t1,t2,t3; + +let $q= +select t1.id, t1.itemid, dt.id, t2.id + from t1, + (select itemid, max(id) as id from t3 where userid = 1 group by itemid) dt, + t2 + where t1.id = dt.id and t1.itemid = dt.itemid and t2.id=t1.itemid; + +set optimizer_switch='split_materialized=on'; +eval explain $q; +eval $q; + +set optimizer_switch='split_materialized=off'; +eval explain $q; +eval $q; + +drop table t1,t2,t3; +set optimizer_switch='split_materialized=default'; + +--echo # End of 10.3 tests diff --git a/sql/opt_split.cc b/sql/opt_split.cc index 395422de3c3..d272638f00c 100644 --- a/sql/opt_split.cc +++ b/sql/opt_split.cc @@ -960,11 +960,7 @@ SplM_plan_info * JOIN_TAB::choose_best_splitting(double record_count, in the cache */ spl_plan= spl_opt_info->find_plan(best_table, best_key, best_key_parts); - if (!spl_plan && - (spl_plan= (SplM_plan_info *) thd->alloc(sizeof(SplM_plan_info))) && - (spl_plan->best_positions= - (POSITION *) thd->alloc(sizeof(POSITION) * join->table_count)) && - !spl_opt_info->plan_cache.push_back(spl_plan)) + if (!spl_plan) { /* The plan for the chosen key has not been found in the cache. @@ -974,6 +970,27 @@ SplM_plan_info * JOIN_TAB::choose_best_splitting(double record_count, reset_validity_vars_for_keyuses(best_key_keyuse_ext_start, best_table, best_key, remaining_tables, true); choose_plan(join, all_table_map & ~join->const_table_map); + + /* + Check that the chosen plan is really a splitting plan. + If not or if there is not enough memory to save the plan in the cache + then just return with no splitting plan. + */ + POSITION *first_non_const_pos= join->best_positions + join->const_tables; + TABLE *table= first_non_const_pos->table->table; + key_map spl_keys= table->keys_usable_for_splitting; + if (!(first_non_const_pos->key && + spl_keys.is_set(first_non_const_pos->key->key)) || + !(spl_plan= (SplM_plan_info *) thd->alloc(sizeof(SplM_plan_info))) || + !(spl_plan->best_positions= + (POSITION *) thd->alloc(sizeof(POSITION) * join->table_count)) || + spl_opt_info->plan_cache.push_back(spl_plan)) + { + reset_validity_vars_for_keyuses(best_key_keyuse_ext_start, best_table, + best_key, remaining_tables, false); + return 0; + } + spl_plan->keyuse_ext_start= best_key_keyuse_ext_start; spl_plan->table= best_table; spl_plan->key= best_key;