diff options
Diffstat (limited to 'sql/item_subselect.cc')
| -rw-r--r-- | sql/item_subselect.cc | 316 |
1 files changed, 193 insertions, 123 deletions
diff --git a/sql/item_subselect.cc b/sql/item_subselect.cc index bffecb3c84c..e19815960a6 100644 --- a/sql/item_subselect.cc +++ b/sql/item_subselect.cc @@ -2,8 +2,7 @@ This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by - the Free Software Foundation; either version 2 of the License, or - (at your option) any later version. + the Free Software Foundation; version 2 of the License. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of @@ -192,16 +191,16 @@ bool Item_subselect::fix_fields(THD *thd_param, Item **ref) return res; } -bool Item_subselect::exec(bool full_scan) +bool Item_subselect::exec() { int res; - res= engine->exec(full_scan); + res= engine->exec(); if (engine_changed) { engine_changed= 0; - return exec(full_scan); + return exec(); } return (res); } @@ -349,6 +348,7 @@ Item_singlerow_subselect::select_transformer(JOIN *join) */ !(select_lex->item_list.head()->type() == FIELD_ITEM || select_lex->item_list.head()->type() == REF_ITEM) && + !join->conds && !join->having && /* switch off this optimization for prepare statement, because we do not rollback this changes @@ -373,8 +373,6 @@ Item_singlerow_subselect::select_transformer(JOIN *join) */ substitution->walk(&Item::remove_dependence_processor, (byte *) select_lex->outer_select()); - /* SELECT without FROM clause can't have WHERE or HAVING clause */ - DBUG_ASSERT(join->conds == 0 && join->having == 0); return RES_REDUCE; } return RES_OK; @@ -450,13 +448,13 @@ bool Item_singlerow_subselect::null_inside() void Item_singlerow_subselect::bring_value() { - exec(FALSE); + exec(); } double Item_singlerow_subselect::val_real() { DBUG_ASSERT(fixed == 1); - if (!exec(FALSE) && !value->null_value) + if (!exec() && !value->null_value) { null_value= 0; return value->val_real(); @@ -471,7 +469,7 @@ double Item_singlerow_subselect::val_real() longlong Item_singlerow_subselect::val_int() { DBUG_ASSERT(fixed == 1); - if (!exec(FALSE) && !value->null_value) + if (!exec() && !value->null_value) { null_value= 0; return value->val_int(); @@ -485,7 +483,7 @@ longlong Item_singlerow_subselect::val_int() String *Item_singlerow_subselect::val_str(String *str) { - if (!exec(FALSE) && !value->null_value) + if (!exec() && !value->null_value) { null_value= 0; return value->val_str(str); @@ -500,7 +498,7 @@ String *Item_singlerow_subselect::val_str(String *str) my_decimal *Item_singlerow_subselect::val_decimal(my_decimal *decimal_value) { - if (!exec(FALSE) && !value->null_value) + if (!exec() && !value->null_value) { null_value= 0; return value->val_decimal(decimal_value); @@ -515,7 +513,7 @@ my_decimal *Item_singlerow_subselect::val_decimal(my_decimal *decimal_value) bool Item_singlerow_subselect::val_bool() { - if (!exec(FALSE) && !value->null_value) + if (!exec() && !value->null_value) { null_value= 0; return value->val_bool(); @@ -567,7 +565,7 @@ bool Item_in_subselect::test_limit(SELECT_LEX_UNIT *unit) Item_in_subselect::Item_in_subselect(Item * left_exp, st_select_lex *select_lex): Item_exists_subselect(), optimizer(0), transformed(0), - enable_pushed_conds(TRUE), upper_item(0) + pushed_cond_guards(NULL), upper_item(0) { DBUG_ENTER("Item_in_subselect::Item_in_subselect"); left_expr= left_exp; @@ -612,7 +610,7 @@ void Item_exists_subselect::fix_length_and_dec() double Item_exists_subselect::val_real() { DBUG_ASSERT(fixed == 1); - if (exec(FALSE)) + if (exec()) { reset(); return 0; @@ -623,7 +621,7 @@ double Item_exists_subselect::val_real() longlong Item_exists_subselect::val_int() { DBUG_ASSERT(fixed == 1); - if (exec(FALSE)) + if (exec()) { reset(); return 0; @@ -634,7 +632,7 @@ longlong Item_exists_subselect::val_int() String *Item_exists_subselect::val_str(String *str) { DBUG_ASSERT(fixed == 1); - if (exec(FALSE)) + if (exec()) { reset(); return 0; @@ -647,7 +645,7 @@ String *Item_exists_subselect::val_str(String *str) my_decimal *Item_exists_subselect::val_decimal(my_decimal *decimal_value) { DBUG_ASSERT(fixed == 1); - if (exec(FALSE)) + if (exec()) { reset(); return 0; @@ -660,7 +658,7 @@ my_decimal *Item_exists_subselect::val_decimal(my_decimal *decimal_value) bool Item_exists_subselect::val_bool() { DBUG_ASSERT(fixed == 1); - if (exec(FALSE)) + if (exec()) { reset(); return 0; @@ -678,7 +676,7 @@ double Item_in_subselect::val_real() DBUG_ASSERT(0); DBUG_ASSERT(fixed == 1); null_value= 0; - if (exec(!enable_pushed_conds)) + if (exec()) { reset(); null_value= 1; @@ -699,7 +697,7 @@ longlong Item_in_subselect::val_int() DBUG_ASSERT(0); DBUG_ASSERT(fixed == 1); null_value= 0; - if (exec(!enable_pushed_conds)) + if (exec()) { reset(); null_value= 1; @@ -720,7 +718,7 @@ String *Item_in_subselect::val_str(String *str) DBUG_ASSERT(0); DBUG_ASSERT(fixed == 1); null_value= 0; - if (exec(!enable_pushed_conds)) + if (exec()) { reset(); null_value= 1; @@ -740,7 +738,7 @@ bool Item_in_subselect::val_bool() { DBUG_ASSERT(fixed == 1); null_value= 0; - if (exec(!enable_pushed_conds)) + if (exec()) { reset(); null_value= 1; @@ -760,7 +758,7 @@ my_decimal *Item_in_subselect::val_decimal(my_decimal *decimal_value) DBUG_ASSERT(0); null_value= 0; DBUG_ASSERT(fixed == 1); - if (exec(!enable_pushed_conds)) + if (exec()) { reset(); null_value= 1; @@ -924,7 +922,7 @@ Item_in_subselect::single_value_transformer(JOIN *join, if (!substitution) { - //first call for this unit + /* We're invoked for the 1st (or the only) SELECT in the subquery UNION */ SELECT_LEX_UNIT *unit= select_lex->master_unit(); substitution= optimizer; @@ -950,19 +948,14 @@ Item_in_subselect::single_value_transformer(JOIN *join, unit->uncacheable|= UNCACHEABLE_DEPENDENT; } + if (!abort_on_null && left_expr->maybe_null && !pushed_cond_guards) + { + if (!(pushed_cond_guards= (bool*)join->thd->alloc(sizeof(bool)))) + DBUG_RETURN(RES_ERROR); + pushed_cond_guards[0]= TRUE; + } select_lex->uncacheable|= UNCACHEABLE_DEPENDENT; - /* - Add the left part of a subselect to a WHERE or HAVING clause of - the right part, e.g. - - SELECT 1 IN (SELECT a FROM t1) => - - SELECT Item_in_optimizer(1, SELECT a FROM t1 WHERE a=1) - - HAVING is used only if the right part contains a SUM function, a GROUP - BY or a HAVING clause. - */ if (join->having || select_lex->with_sum_func || select_lex->group_list.elements) { @@ -974,13 +967,13 @@ Item_in_subselect::single_value_transformer(JOIN *join, ref_pointer_array, (char *)"<ref>", this->full_name())); - if (!abort_on_null && ((Item*)select_lex->item_list.head())->maybe_null) + if (!abort_on_null && left_expr->maybe_null) { /* We can encounter "NULL IN (SELECT ...)". Wrap the added condition - within a trigger. + within a trig_cond. */ - item= new Item_func_trig_cond(item, &enable_pushed_conds); + item= new Item_func_trig_cond(item, get_cond_guard(0)); } /* @@ -989,6 +982,8 @@ Item_in_subselect::single_value_transformer(JOIN *join, argument (reference) to fix_fields() */ select_lex->having= join->having= and_items(join->having, item); + if (join->having == item) + item->name= (char*)in_having_cond; select_lex->having_fix_field= 1; /* we do not check join->having->fixed, because Item_and (from and_items) @@ -1015,14 +1010,19 @@ Item_in_subselect::single_value_transformer(JOIN *join, item= func->create(expr, item); if (!abort_on_null && orig_item->maybe_null) { - having= - new Item_func_trig_cond(new Item_is_not_null_test(this, having), - &enable_pushed_conds); + having= new Item_is_not_null_test(this, having); + if (left_expr->maybe_null) + { + if (!(having= new Item_func_trig_cond(having, + get_cond_guard(0)))) + DBUG_RETURN(RES_ERROR); + } /* Item_is_not_null_test can't be changed during fix_fields() we can assign select_lex->having here, and pass 0 as last argument (reference) to fix_fields() */ + having->name= (char*)in_having_cond; select_lex->having= join->having= having; select_lex->having_fix_field= 1; /* @@ -1034,17 +1034,25 @@ Item_in_subselect::single_value_transformer(JOIN *join, select_lex->having_fix_field= 0; if (tmp) DBUG_RETURN(RES_ERROR); - /* - NOTE: It is important that we add this "IS NULL" here, even when - orig_item can't be NULL. This is needed so that this predicate is - only used by ref[_or_null] analyzer (and, e.g. is not used by const - propagation). - */ item= new Item_cond_or(item, new Item_func_isnull(orig_item)); - item= new Item_func_trig_cond(item, &enable_pushed_conds); } + /* + If we may encounter NULL IN (SELECT ...) and care whether subquery + result is NULL or FALSE, wrap condition in a trig_cond. + */ + if (!abort_on_null && left_expr->maybe_null) + { + if (!(item= new Item_func_trig_cond(item, get_cond_guard(0)))) + DBUG_RETURN(RES_ERROR); + } + /* + TODO: figure out why the following is done here in + single_value_transformer but there is no corresponding action in + row_value_transformer? + */ item->name= (char *)in_additional_cond; + /* AND can't be changed during fix_fields() we can assign select_lex->having here, and pass 0 as last @@ -1075,10 +1083,16 @@ Item_in_subselect::single_value_transformer(JOIN *join, select_lex->ref_pointer_array, (char *)"<no matter>", (char *)"<result>")); - new_having= new Item_func_trig_cond(new_having, &enable_pushed_conds); + if (!abort_on_null && left_expr->maybe_null) + { + if (!(new_having= new Item_func_trig_cond(new_having, + get_cond_guard(0)))) + DBUG_RETURN(RES_ERROR); + } + new_having->name= (char*)in_having_cond; select_lex->having= join->having= new_having; - select_lex->having_fix_field= 1; + /* we do not check join->having->fixed, because comparison function (from func->create) can't be fixed after creation @@ -1148,6 +1162,15 @@ Item_in_subselect::row_value_transformer(JOIN *join) thd->lex->current_select= current; unit->uncacheable|= UNCACHEABLE_DEPENDENT; + + if (!abort_on_null && left_expr->maybe_null && !pushed_cond_guards) + { + if (!(pushed_cond_guards= (bool*)join->thd->alloc(sizeof(bool) * + left_expr->cols()))) + DBUG_RETURN(RES_ERROR); + for (uint i= 0; i < cols_num; i++) + pushed_cond_guards[i]= TRUE; + } } select_lex->uncacheable|= UNCACHEABLE_DEPENDENT; @@ -1164,6 +1187,7 @@ Item_in_subselect::row_value_transformer(JOIN *join) is_not_null_test(v3)) where is_not_null_test used to register nulls in case if we have not found matching to return correct NULL value + TODO: say here explicitly if the order of AND parts matters or not. */ Item *item_having_part2= 0; for (uint i= 0; i < cols_num; i++) @@ -1192,21 +1216,28 @@ Item_in_subselect::row_value_transformer(JOIN *join) (char *)"<no matter>", (char *)"<list ref>") ); - having_item= - and_items(having_item, - new Item_cond_or(item_eq, item_isnull)); - item_having_part2= - and_items(item_having_part2, - new - Item_is_not_null_test(this, - new - Item_ref(&select_lex->context, - select_lex-> - ref_pointer_array + i, - (char *)"<no matter>", - (char *)"<list ref>") - ) - ); + Item *col_item= new Item_cond_or(item_eq, item_isnull); + if (!abort_on_null && left_expr->el(i)->maybe_null) + { + if (!(col_item= new Item_func_trig_cond(col_item, get_cond_guard(i)))) + DBUG_RETURN(RES_ERROR); + } + having_item= and_items(having_item, col_item); + + Item *item_nnull_test= + new Item_is_not_null_test(this, + new Item_ref(&select_lex->context, + select_lex-> + ref_pointer_array + i, + (char *)"<no matter>", + (char *)"<list ref>")); + if (!abort_on_null && left_expr->el(i)->maybe_null) + { + if (!(item_nnull_test= + new Item_func_trig_cond(item_nnull_test, get_cond_guard(i)))) + DBUG_RETURN(RES_ERROR); + } + item_having_part2= and_items(item_having_part2, item_nnull_test); item_having_part2->top_level_item(); } having_item= and_items(having_item, item_having_part2); @@ -1255,18 +1286,15 @@ Item_in_subselect::row_value_transformer(JOIN *join) ); if (!abort_on_null) { - having_item= - and_items(having_item, - new - Item_is_not_null_test(this, - new - Item_ref(&select_lex->context, - select_lex-> - ref_pointer_array + i, - (char *)"<no matter>", - (char *)"<list ref>") - ) - ); + Item *having_col_item= + new Item_is_not_null_test(this, + new + Item_ref(&select_lex->context, + select_lex->ref_pointer_array + i, + (char *)"<no matter>", + (char *)"<list ref>")); + + item_isnull= new Item_func_isnull(new Item_direct_ref(&select_lex->context, @@ -1275,14 +1303,23 @@ Item_in_subselect::row_value_transformer(JOIN *join) (char *)"<no matter>", (char *)"<list ref>") ); - item= new Item_cond_or(item, item_isnull); + /* + TODO: why we create the above for cases where the right part + cant be NULL? + */ + if (left_expr->el(i)->maybe_null) + { + if (!(item= new Item_func_trig_cond(item, get_cond_guard(i)))) + DBUG_RETURN(RES_ERROR); + if (!(having_col_item= + new Item_func_trig_cond(having_col_item, get_cond_guard(i)))) + DBUG_RETURN(RES_ERROR); + } + having_item= and_items(having_item, having_col_item); } - where_item= and_items(where_item, item); } - if (where_item) - where_item= new Item_func_trig_cond(where_item, &enable_pushed_conds); /* AND can't be changed during fix_fields() we can assign select_lex->where here, and pass 0 as last @@ -1296,9 +1333,9 @@ Item_in_subselect::row_value_transformer(JOIN *join) if (having_item) { bool res; - having_item= new Item_func_trig_cond(having_item, &enable_pushed_conds); - select_lex->having= join->having= and_items(join->having, having_item); + if (having_item == select_lex->having) + having_item->name= (char*)in_having_cond; select_lex->having->top_level_item(); /* AND can't be changed during fix_fields() @@ -1684,7 +1721,7 @@ int init_read_record_seq(JOIN_TAB *tab); int join_read_always_key_or_null(JOIN_TAB *tab); int join_read_next_same_or_null(READ_RECORD *info); -int subselect_single_select_engine::exec(bool full_scan) +int subselect_single_select_engine::exec() { DBUG_ENTER("subselect_single_select_engine::exec"); char const *save_where= thd->where; @@ -1722,9 +1759,13 @@ int subselect_single_select_engine::exec(bool full_scan) if (!executed) { item->reset_value_registration(); - if (full_scan) + bool have_changed_access= FALSE; + JOIN_TAB *changed_tabs[MAX_TABLES]; + JOIN_TAB **last_changed_tab= changed_tabs; + if (item->have_guarded_conds()) { /* + For at least one of the pushed predicates the following is true: We should not apply optimizations based on the condition that was pushed down into the subquery. Those optimizations are ref[_or_null] acceses. Change them to be full table scans. @@ -1732,32 +1773,36 @@ int subselect_single_select_engine::exec(bool full_scan) for (uint i=join->const_tables ; i < join->tables ; i++) { JOIN_TAB *tab=join->join_tab+i; - if (tab->keyuse && tab->keyuse->outer_ref) + if (tab && tab->keyuse) { - tab->read_first_record= init_read_record_seq; - tab->read_record.record= tab->table->record[0]; - tab->read_record.thd= join->thd; - tab->read_record.ref_length= tab->table->file->ref_length; + for (uint i= 0; i < tab->ref.key_parts; i++) + { + bool *cond_guard= tab->ref.cond_guards[i]; + if (cond_guard && !*cond_guard) + { + /* Change the access method to full table scan */ + tab->read_first_record= init_read_record_seq; + tab->read_record.record= tab->table->record[0]; + tab->read_record.thd= join->thd; + tab->read_record.ref_length= tab->table->file->ref_length; + *(last_changed_tab++)= tab; + break; + } + } } } } join->exec(); - if (full_scan) + /* Enable the optimizations back */ + for (JOIN_TAB **ptab= changed_tabs; ptab != last_changed_tab; ptab++) { - /* Enable the optimizations back */ - for (uint i=join->const_tables ; i < join->tables ; i++) - { - JOIN_TAB *tab=join->join_tab+i; - if (tab->keyuse && tab->keyuse->outer_ref) - { - tab->read_record.record= 0; - tab->read_record.ref_length= 0; - tab->read_first_record= join_read_always_key_or_null; - tab->read_record.read_record= join_read_next_same_or_null; - } - } + JOIN_TAB *tab= *ptab; + tab->read_record.record= 0; + tab->read_record.ref_length= 0; + tab->read_first_record= join_read_always_key_or_null; + tab->read_record.read_record= join_read_next_same_or_null; } executed= 1; thd->where= save_where; @@ -1769,13 +1814,9 @@ int subselect_single_select_engine::exec(bool full_scan) DBUG_RETURN(0); } -int subselect_union_engine::exec(bool full_scan) +int subselect_union_engine::exec() { char const *save_where= thd->where; - /* - Ignore the full_scan parameter: the pushed down predicates are only used - for filtering, and the caller has disabled them if necessary. - */ int res= unit->exec(); thd->where= save_where; return res; @@ -1783,7 +1824,7 @@ int subselect_union_engine::exec(bool full_scan) /* - Search for at least on row satisfying select condition + Search for at least one row satisfying select condition SYNOPSIS subselect_uniquesubquery_engine::scan_table() @@ -1792,8 +1833,8 @@ int subselect_union_engine::exec(bool full_scan) Scan the table using sequential access until we find at least one row satisfying select condition. - The result of this function (info about whether a row was found) is - stored in this->empty_result_set. + The caller must set this->empty_result_set=FALSE before calling this + function. This function will set it to TRUE if it finds a matching row. RETURN FALSE - OK @@ -1805,7 +1846,6 @@ int subselect_uniquesubquery_engine::scan_table() int error; TABLE *table= tab->table; DBUG_ENTER("subselect_uniquesubquery_engine::scan_table"); - empty_result_set= TRUE; if (table->file->inited) table->file->ha_index_end(); @@ -1898,10 +1938,13 @@ bool subselect_uniquesubquery_engine::copy_ref_key() - FALSE otherwise. In some cases (IN subselect is a top level item, i.e. abort_on_null==TRUE) - the caller doesn't distinguish between NULL and FALSE result and we just + the caller doesn't distinguish between NULL and FALSE result and we just return FALSE. - Otherwise we make a full table scan to see if there is at least one matching row. - + Otherwise we make a full table scan to see if there is at least one + matching row. + + The result of this function (info about whether a row was found) is + stored in this->empty_result_set. NOTE RETURN @@ -1909,11 +1952,12 @@ bool subselect_uniquesubquery_engine::copy_ref_key() TRUE - an error occured while scanning */ -int subselect_uniquesubquery_engine::exec(bool full_scan) +int subselect_uniquesubquery_engine::exec() { DBUG_ENTER("subselect_uniquesubquery_engine::exec"); int error; TABLE *table= tab->table; + empty_result_set= TRUE; /* TODO: change to use of 'full_scan' here? */ if (copy_ref_key()) @@ -1934,9 +1978,13 @@ int subselect_uniquesubquery_engine::exec(bool full_scan) { error= 0; table->null_row= 0; - ((Item_in_subselect *) item)->value= (!table->status && - (!cond || cond->val_int()) ? 1 : - 0); + if (!table->status && (!cond || cond->val_int())) + { + ((Item_in_subselect *) item)->value= 1; + empty_result_set= FALSE; + } + else + ((Item_in_subselect *) item)->value= 0; } DBUG_RETURN(error != 0); @@ -2002,7 +2050,7 @@ subselect_uniquesubquery_engine::~subselect_uniquesubquery_engine() 1 */ -int subselect_indexsubquery_engine::exec(bool full_scan) +int subselect_indexsubquery_engine::exec() { DBUG_ENTER("subselect_indexsubquery_engine::exec"); int error; @@ -2043,8 +2091,9 @@ int subselect_indexsubquery_engine::exec(bool full_scan) table->null_row= 0; if (!table->status) { - if (!cond || cond->val_int()) + if ((!cond || cond->val_int()) && (!having || having->val_int())) { + empty_result_set= FALSE; if (null_finding) ((Item_in_subselect *) item)->was_null= 1; else @@ -2187,11 +2236,16 @@ void subselect_indexsubquery_engine::print(String *str) str->append(key_info->name); if (check_null) str->append(STRING_WITH_LEN(" checking NULL")); - if (cond) + if (cond) { str->append(STRING_WITH_LEN(" where ")); cond->print(str); } + if (having) + { + str->append(STRING_WITH_LEN(" having ")); + having->print(str); + } str->append(')'); } @@ -2278,6 +2332,22 @@ bool subselect_single_select_engine::no_tables() /* + Check statically whether the subquery can return NULL + + SINOPSYS + subselect_single_select_engine::may_be_null() + + RETURN + FALSE can guarantee that the subquery never return NULL + TRUE otherwise +*/ +bool subselect_single_select_engine::may_be_null() +{ + return ((no_tables() && !join->conds && !join->having) ? maybe_null : 1); +} + + +/* Report about presence of tables in subquery SYNOPSIS |