diff options
Diffstat (limited to 'sql/opt_subselect.cc')
| -rw-r--r-- | sql/opt_subselect.cc | 63 |
1 files changed, 56 insertions, 7 deletions
diff --git a/sql/opt_subselect.cc b/sql/opt_subselect.cc index fa338f0e60c..cd88e7856a2 100644 --- a/sql/opt_subselect.cc +++ b/sql/opt_subselect.cc @@ -533,6 +533,31 @@ bool is_materialization_applicable(THD *thd, Item_in_subselect *in_subs, } +/** + @brief Check whether an IN subquery must be excluded from conversion to SJ + + @param thd global context the processed statement + @returns true if the IN subquery must be excluded from conversion to SJ + + @note + Currently a top level IN subquery of an update/delete statement + is not converted to SJ if the statement contains ORDER BY ... LIMIT + or contains RETURNING. +*/ + +bool SELECT_LEX::is_sj_conversion_prohibited(THD *thd) +{ + DBUG_ASSERT(master_unit()->item->substype() == Item_subselect::IN_SUBS); + SELECT_LEX *outer_sl= outer_select(); + return !outer_sl->outer_select() && + (thd->lex->sql_command == SQLCOM_UPDATE || + thd->lex->sql_command == SQLCOM_DELETE) && + ((outer_sl->order_list.elements && + outer_sl->get_limit() != HA_POS_ERROR) || + (thd->lex->sql_command == SQLCOM_DELETE && + thd->lex->has_returning())); +} + /* Check if we need JOIN::prepare()-phase subquery rewrites and if yes, do them @@ -675,9 +700,9 @@ int check_and_do_in_subquery_rewrites(JOIN *join) 3. Subquery does not have GROUP BY or ORDER BY 4. Subquery does not use aggregate functions or HAVING 5. Subquery predicate is at the AND-top-level of ON/WHERE clause - 6. We are not in a subquery of a single table UPDATE/DELETE that - doesn't have a JOIN (TODO: We should handle this at some - point by switching to multi-table UPDATE/DELETE) + 6. We are not in a top level subquery of a single-table UPDATE or + DELETE with ORDER BY ... LIMIT and we are not in a top level + subquery of a single-table DELETE with returning 7. We're not in a table-less subquery like "SELECT 1" 8. No execution method was already chosen (by a prepared statement) 9. Parent select is not a table-less select @@ -692,9 +717,7 @@ int check_and_do_in_subquery_rewrites(JOIN *join) !select_lex->group_list.elements && !join->order && // 3 !join->having && !select_lex->with_sum_func && // 4 in_subs->emb_on_expr_nest && // 5 - select_lex->outer_select()->join && // 6 - (!thd->lex->m_sql_cmd || - thd->lex->m_sql_cmd->sql_command_code() == SQLCOM_UPDATE_MULTI) && + !select_lex->is_sj_conversion_prohibited(thd) && // 6 parent_unit->first_select()->leaf_tables.elements && // 7 !in_subs->has_strategy() && // 8 select_lex->outer_select()->table_list.first && // 9 @@ -754,7 +777,8 @@ int check_and_do_in_subquery_rewrites(JOIN *join) */ if (in_subs && !in_subs->has_strategy()) { - if (is_materialization_applicable(thd, in_subs, select_lex)) + if (!select_lex->is_sj_conversion_prohibited(thd) && + is_materialization_applicable(thd, in_subs, select_lex)) { in_subs->add_strategy(SUBS_MATERIALIZATION); @@ -7260,3 +7284,28 @@ bool TABLE_LIST::is_sjm_scan_table() { return is_active_sjm() && sj_mat_info->is_sj_scan; } + + +/** + @brief Check whether this subselect can be lifted to the top level + @returns true if the test is positive, false otherwise +*/ + +bool SELECT_LEX::is_sj_subselect_lifted_to_top() +{ + st_select_lex *sl= this; + st_select_lex *outer_sl= outer_select(); + for ( ; outer_sl; sl= outer_sl, outer_sl= outer_sl->outer_select()) + { + List_iterator_fast<Item_in_subselect> it(outer_sl->sj_subselects); + Item_in_subselect *in_subs; + while ((in_subs= it++)) + { + if (in_subs->unit->first_select() == sl) + break; + } + if (!in_subs) + return false; + } + return true; +} |