diff options
Diffstat (limited to 'sql/sql_select.cc')
| -rw-r--r-- | sql/sql_select.cc | 33 |
1 files changed, 32 insertions, 1 deletions
diff --git a/sql/sql_select.cc b/sql/sql_select.cc index 6a441c5047b..57ffd58f8b4 100644 --- a/sql/sql_select.cc +++ b/sql/sql_select.cc @@ -2382,6 +2382,9 @@ int JOIN::optimize_stage2() if (subq_exit_fl) goto setup_subq_exit; + if (zero_result_cause) + goto setup_subq_exit; + if (unlikely(thd->check_killed())) DBUG_RETURN(1); @@ -2418,6 +2421,8 @@ int JOIN::optimize_stage2() DBUG_PRINT("error",("Error: initialize_tables() failed")); DBUG_RETURN(1); // error == -1 } + + /* ConstRowNotFoundShortcut-2: */ if (const_table_map != found_const_table_map && !(select_options & SELECT_DESCRIBE)) { @@ -2603,6 +2608,7 @@ int JOIN::optimize_stage2() } } + /* ConstRowNotFoundShortcut-3: */ if (conds && const_table_map != found_const_table_map && (select_options & SELECT_DESCRIBE)) { @@ -5392,7 +5398,32 @@ make_join_statistics(JOIN *join, List<TABLE_LIST> &tables_list, } } } while (ref_changed); - + + /* + ConstRowNotFoundShortcut-1: + Some constant/system tables have mo matching rows. This means that + the join operation output will be empty. + Short-cut further optimization steps. + Note that some query plan steps will still be performed to handle + implicit grouping, join result setup, etc. + See also: ConstRowNotFoundShortcut-{2,3}. + + Do not do this if we're optimizing for some UNION's fake_select_lex. + We might be running UglySubqueryReoptimization (grep for name) and + in this case constant tables are not reliable. + */ + if ((join->const_table_map & ~found_const_table_map) && + !(join->select_lex->master_unit() && + join->select_lex->master_unit()->fake_select_lex == join->select_lex)) + { + join->zero_result_cause= "no matching row in const table"; + join->table_count=0; + join->const_tables= 0; + join->join_tab= NULL; + + DBUG_RETURN(0); + } + join->sort_by_table= get_sort_by_table(join->order, join->group_list, join->select_lex->leaf_tables, join->const_table_map); |