diff options
Diffstat (limited to 'sql/opt_subselect.cc')
| -rw-r--r-- | sql/opt_subselect.cc | 54 |
1 files changed, 49 insertions, 5 deletions
diff --git a/sql/opt_subselect.cc b/sql/opt_subselect.cc index 75ec8fb6665..1bdbcf0deb9 100644 --- a/sql/opt_subselect.cc +++ b/sql/opt_subselect.cc @@ -30,6 +30,8 @@ #include "sql_base.h" #include "sql_const.h" #include "sql_select.h" +#include "sql_update.h" // class Sql_cmd_update +#include "sql_delete.h" // class Sql_cmd_delete #include "filesort.h" #include "opt_subselect.h" #include "sql_test.h" @@ -534,6 +536,48 @@ bool is_materialization_applicable(THD *thd, Item_in_subselect *in_subs, return FALSE; } +/** + @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 delete statement is not converted + to SJ if the statement contains ORDER BY ... LIMIT or contains RETURNING. + + @todo + The disjunctive members + !((Sql_cmd_update *) cmd)->is_multitable() + !((Sql_cmd_delete *) cmd)->is_multitable() + will be removed when conversions of IN predicands to semi-joins are + fully supported for single-table UPDATE/DELETE statements. +*/ + +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(); + if (outer_sl->outer_select()) + return false; + + Sql_cmd *cmd= thd->lex->m_sql_cmd; + + switch (thd->lex->sql_command) { + case SQLCOM_UPDATE: + return + !((Sql_cmd_update *) cmd)->is_multitable() && + ((Sql_cmd_update *) cmd)->processing_as_multitable_update_prohibited(thd); + case SQLCOM_DELETE: + return + !((Sql_cmd_delete *) cmd)->is_multitable() && + ((Sql_cmd_delete *) cmd)->processing_as_multitable_delete_prohibited(thd); + default: + return false; + } +} + /* Check if we need JOIN::prepare()-phase subquery rewrites and if yes, do them @@ -677,9 +721,8 @@ 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 subquery of a single-table UPDATE/DELETE that + does not allow conversion to multi-table UPDATE/DELETE 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 @@ -698,7 +741,7 @@ 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 + !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 @@ -758,7 +801,8 @@ 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); |