From b8b1b928ffa9da49588eec4ebe05c864c9847be2 Mon Sep 17 00:00:00 2001 From: Sergei Petrunia Date: Fri, 14 Oct 2016 00:05:13 +0300 Subject: [PATCH] MDEV-8359: WHERE condition referring to inner table of left join can be sargable Implement a technique mentioned in the MDEV. Under certain conditions, cond(inner_table.col) can be substituted for cond(outer_table.col) for the purpose of range analysis. --- mysql-test/r/join_outer.result | 23 +++++++++++++++++ mysql-test/t/join_outer.test | 22 +++++++++++++++++ sql/opt_range.cc | 45 ++++++++++++++++++++++++++++++++++ 3 files changed, 90 insertions(+) diff --git a/mysql-test/r/join_outer.result b/mysql-test/r/join_outer.result index 8b4ee17f20e..77932b65857 100644 --- a/mysql-test/r/join_outer.result +++ b/mysql-test/r/join_outer.result @@ -2337,4 +2337,27 @@ id select_type table type possible_keys key key_len ref rows filtered Extra Warnings: Note 1003 select `test`.`t1`.`i1` AS `i1`,`test`.`t1`.`v1` AS `v1`,`test`.`t2`.`i2` AS `i2`,`test`.`t2`.`v2` AS `v2`,`test`.`t3`.`i3` AS `i3`,`test`.`t3`.`v3` AS `v3` from `test`.`t1` join `test`.`t2` join `test`.`t3` where ((`test`.`t3`.`v3` = 4) and (`test`.`t1`.`i1` = `test`.`t3`.`i3`) and (`test`.`t2`.`i2` = `test`.`t3`.`i3`)) drop table t1,t2,t3; +# +# MDEV-8359: WHERE condition referring to inner table of left join can be sargable +# +create table t0 (a int); +insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9); +create table t1 (a int, b int, key(a)); +insert into t1 select A.a+10*B.a+100*C.a, A.a+10*B.a+100*C.a from t0 A, t0 B, t0 C; +create table t2 (a int, b int); +insert into t2 select a,a from t0; +# The following must remain an outer join +# but it must be able to use range access on table t1: +explain extended +select * +from +t1 left join t2 on t2.a=t1.a +where +t1.a<3 or t2.a<4; +id select_type table type possible_keys key key_len ref rows filtered Extra +1 SIMPLE t1 range a a 5 NULL 4 100.00 Using index condition +1 SIMPLE t2 ALL NULL NULL NULL NULL 10 100.00 Using where +Warnings: +Note 1003 select `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b`,`test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b` from `test`.`t1` left join `test`.`t2` on((`test`.`t2`.`a` = `test`.`t1`.`a`)) where ((`test`.`t1`.`a` < 3) or (`test`.`t2`.`a` < 4)) +drop table t0,t1, t2; SET optimizer_switch=@save_optimizer_switch; diff --git a/mysql-test/t/join_outer.test b/mysql-test/t/join_outer.test index a3a1278ef1e..f0ecbe29149 100644 --- a/mysql-test/t/join_outer.test +++ b/mysql-test/t/join_outer.test @@ -1882,4 +1882,26 @@ WHERE v3 = 4; drop table t1,t2,t3; +--echo # +--echo # MDEV-8359: WHERE condition referring to inner table of left join can be sargable +--echo # +create table t0 (a int); +insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9); + +create table t1 (a int, b int, key(a)); +insert into t1 select A.a+10*B.a+100*C.a, A.a+10*B.a+100*C.a from t0 A, t0 B, t0 C; + +create table t2 (a int, b int); +insert into t2 select a,a from t0; + +--echo # The following must remain an outer join +--echo # but it must be able to use range access on table t1: +explain extended +select * +from + t1 left join t2 on t2.a=t1.a +where + t1.a<3 or t2.a<4; + +drop table t0,t1, t2; SET optimizer_switch=@save_optimizer_switch; diff --git a/sql/opt_range.cc b/sql/opt_range.cc index 3ea9f4e5db9..1713936da3e 100644 --- a/sql/opt_range.cc +++ b/sql/opt_range.cc @@ -7328,6 +7328,51 @@ SEL_TREE *Item_bool_func::get_full_func_mm_tree(RANGE_OPT_PARAM *param, } } } + else + { + THD *thd= current_thd; + JOIN *join; + COND_EQUAL *cond_equal; + // todo: also check that the condition has abort_on_null set. + if ((field_item->used_tables() & ~OUTER_REF_TABLE_BIT) && + thd->lex->current_select && + (join= thd->lex->current_select->join) && + (join->outer_join & field_item->used_tables()) && + (cond_equal= field->table->pos_in_table_list->cond_equal) && + field_item->used_tables() & not_null_tables()) + { + // Ok this is a table that's inner w.r.t some outer join + // And it has a multiple equality + List_iterator li(cond_equal->current_level); + Item_equal *cur_item_eq; + while ((cur_item_eq= li++)) + { + // If the multiple equality contains fields from + // - the table we're doing range analysis for + // - the table that we have a field from + // and field that we have is also there + if ((cur_item_eq->used_tables() & (param->current_table | + field->table->map)) && + cur_item_eq->contains(field)) + { + // Find fields in the table we're from + Item_equal_fields_iterator it(*cur_item_eq); + while (it++) + { + Field *f= it.get_curr_field(); + if (f->table == param->table) + { + if (!((ref_tables | f->table->map) & param_comp)) + { + tree= get_func_mm_tree(param, f, value); + ftree= !ftree ? tree : tree_and(param, ftree, tree); + } + } + } + } + } + } + } DBUG_RETURN(ftree); }