diff options
| -rw-r--r-- | sql/sql_select.cc | 2 | ||||
| -rw-r--r-- | sql/sql_select.h | 10 | ||||
| -rw-r--r-- | sql/sql_union.cc | 57 |
3 files changed, 51 insertions, 18 deletions
diff --git a/sql/sql_select.cc b/sql/sql_select.cc index c62a19b2752..ebc48c2967c 100644 --- a/sql/sql_select.cc +++ b/sql/sql_select.cc @@ -2416,7 +2416,7 @@ make_join_statistics(JOIN *join, TABLE_LIST *tables, COND *conds, if ((table->s->system || table->file->records <= 1) && ! s->dependent && !(table->file->table_flags() & HA_NOT_EXACT_COUNT) && - !table->fulltext_searched) + !table->fulltext_searched && !join->no_const_tables) { set_position(join,const_count++,s,(KEYUSE*) 0); } diff --git a/sql/sql_select.h b/sql/sql_select.h index 4f9f6e9ed48..5be4f111bef 100644 --- a/sql/sql_select.h +++ b/sql/sql_select.h @@ -277,6 +277,14 @@ public: SELECT_LEX_UNIT *unit; // select that processed SELECT_LEX *select_lex; + /* + TRUE <=> optimizer must not mark any table as a constant table. + This is needed for subqueries in form "a IN (SELECT .. UNION SELECT ..): + when we optimize the select that reads the results of the union from a + temporary table, we must not mark the temp. table as constant because + the number of rows in it may vary from one subquery execution to another. + */ + bool no_const_tables; JOIN *tmp_join; // copy of this JOIN to be used with temporary tables ROLLUP rollup; // Used with rollup @@ -397,6 +405,8 @@ public: tmp_table_param.init(); tmp_table_param.end_write_records= HA_POS_ERROR; rollup.state= ROLLUP::STATE_NONE; + + no_const_tables= FALSE; } int prepare(Item ***rref_pointer_array, TABLE_LIST *tables, uint wind_num, diff --git a/sql/sql_union.cc b/sql/sql_union.cc index 373b03d45e6..16c4eeab4bb 100644 --- a/sql/sql_union.cc +++ b/sql/sql_union.cc @@ -545,6 +545,10 @@ bool st_select_lex_unit::exec() /* allocate JOIN for fake select only once (prevent mysql_select automatic allocation) + TODO: The above is nonsense. mysql_select() will not allocate the + join if one already exists. There must be some other reason why we + don't let it allocate the join. Perhaps this is because we need + some special parameter values passed to join constructor? */ if (!(fake_select_lex->join= new JOIN(thd, item_list, fake_select_lex->options, result))) @@ -552,33 +556,52 @@ bool st_select_lex_unit::exec() fake_select_lex->table_list.empty(); DBUG_RETURN(TRUE); } + fake_select_lex->join->no_const_tables= TRUE; /* Fake st_select_lex should have item list for correctref_array allocation. */ fake_select_lex->item_list= item_list; + saved_error= mysql_select(thd, &fake_select_lex->ref_pointer_array, + &result_table_list, + 0, item_list, NULL, + global_parameters->order_list.elements, + (ORDER*)global_parameters->order_list.first, + (ORDER*) NULL, NULL, (ORDER*) NULL, + fake_select_lex->options | SELECT_NO_UNLOCK, + result, this, fake_select_lex); } else { - JOIN_TAB *tab,*end; - for (tab=join->join_tab, end=tab+join->tables ; - tab && tab != end ; - tab++) - { - delete tab->select; - delete tab->quick; - } - join->init(thd, item_list, fake_select_lex->options, result); + if (describe) + { + /* + In EXPLAIN command, constant subqueries that do not use any + tables are executed two times: + - 1st time is a real evaluation to get the subquery value + - 2nd time is to produce EXPLAIN output rows. + 1st execution sets certain members (e.g. select_result) to perform + subquery execution rather than EXPLAIN line production. In order + to reset them back, we re-do all of the actions (yes it is ugly): + */ + join->init(thd, item_list, fake_select_lex->options, result); + saved_error= mysql_select(thd, &fake_select_lex->ref_pointer_array, + &result_table_list, + 0, item_list, NULL, + global_parameters->order_list.elements, + (ORDER*)global_parameters->order_list.first, + (ORDER*) NULL, NULL, (ORDER*) NULL, + fake_select_lex->options | SELECT_NO_UNLOCK, + result, this, fake_select_lex); + } + else + { + join->examined_rows= 0; + join->reinit(); + saved_error= join->exec(); + } } - saved_error= mysql_select(thd, &fake_select_lex->ref_pointer_array, - &result_table_list, - 0, item_list, NULL, - global_parameters->order_list.elements, - (ORDER*)global_parameters->order_list.first, - (ORDER*) NULL, NULL, (ORDER*) NULL, - fake_select_lex->options | SELECT_NO_UNLOCK, - result, this, fake_select_lex); fake_select_lex->table_list.empty(); if (!saved_error) |