diff options
Diffstat (limited to 'sql/sql_lex.cc')
| -rw-r--r-- | sql/sql_lex.cc | 156 |
1 files changed, 140 insertions, 16 deletions
diff --git a/sql/sql_lex.cc b/sql/sql_lex.cc index 19e5acfa64c..6f1d8b815fe 100644 --- a/sql/sql_lex.cc +++ b/sql/sql_lex.cc @@ -7245,9 +7245,9 @@ void st_select_lex::collect_grouping_fields(THD *thd, { if ((*ord->item)->eq((Item*)item, 0)) { - Grouping_tmp_field *grouping_tmp_field= - new Grouping_tmp_field(master_unit()->derived->table->field[i], item); - grouping_tmp_fields.push_back(grouping_tmp_field); + Field_pair *grouping_tmp_field= + new Field_pair(master_unit()->derived->table->field[i], item); + grouping_tmp_fields.push_back(grouping_tmp_field); } } } @@ -7277,8 +7277,7 @@ void st_select_lex::collect_grouping_fields(THD *thd, */ void -st_select_lex::check_cond_extraction_for_grouping_fields(Item *cond, - TABLE_LIST *derived) +st_select_lex::check_cond_extraction_for_grouping_fields(Item *cond) { cond->clear_extraction_flag(); if (cond->type() == Item::COND_ITEM) @@ -7291,7 +7290,7 @@ st_select_lex::check_cond_extraction_for_grouping_fields(Item *cond, Item *item; while ((item=li++)) { - check_cond_extraction_for_grouping_fields(item, derived); + check_cond_extraction_for_grouping_fields(item); if (item->get_extraction_flag() != NO_EXTRACTION_FL) { count++; @@ -7340,7 +7339,7 @@ st_select_lex::check_cond_extraction_for_grouping_fields(Item *cond, to figure out whether a subformula depends only on these fields or not. @note The built condition C is always implied by the condition cond - (cond => C). The method tries to build the most restictive such + (cond => C). The method tries to build the least restictive such condition (i.e. for any other condition C' such that cond => C' we have C => C'). @note @@ -7353,7 +7352,7 @@ st_select_lex::check_cond_extraction_for_grouping_fields(Item *cond, */ Item *st_select_lex::build_cond_for_grouping_fields(THD *thd, Item *cond, - bool no_top_clones) + bool no_top_clones) { if (cond->get_extraction_flag() == FULL_EXTRACTION_FL) { @@ -7381,17 +7380,17 @@ Item *st_select_lex::build_cond_for_grouping_fields(THD *thd, Item *cond, { if (item->get_extraction_flag() == NO_EXTRACTION_FL) { - DBUG_ASSERT(cond_and); - item->clear_extraction_flag(); - continue; + DBUG_ASSERT(cond_and); + item->clear_extraction_flag(); + continue; } Item *fix= build_cond_for_grouping_fields(thd, item, - no_top_clones & cond_and); + no_top_clones & cond_and); if (!fix) { - if (cond_and) - continue; - break; + if (cond_and) + continue; + break; } new_cond->argument_list()->push_back(fix, thd->mem_root); } @@ -7399,7 +7398,7 @@ Item *st_select_lex::build_cond_for_grouping_fields(THD *thd, Item *cond, if (!cond_and && item) { while((item= li++)) - item->clear_extraction_flag(); + item->clear_extraction_flag(); return 0; } switch (new_cond->argument_list()->elements) @@ -7757,3 +7756,128 @@ Item *Lex_trim_st::make_item_func_trim(THD *thd) const make_item_func_trim_oracle(thd) : make_item_func_trim_std(thd); } + + +/** + @brief + Extract from given item a condition pushable into WHERE clause + + @param thd the thread handle + @param cond the item to extract a condition to be pushed + into WHERE + @param remaining_cond the condition that will remain of cond after + the pushdown of its parts into the WHERE clause + @param transformer the transformer callback function to be + applied to the condition so it can be pushed + down into the WHERE clause of this select + @param arg parameter to be passed to the transformer + + @details + This method checks if cond entirely or its parts can be + pushed into the WHERE clause of this select and prepares it for pushing. + + First it checks wherever this select doesn't have any aggregation function + in its projection and GROUP BY clause. If so cond can be entirely + pushed into the WHERE clause of this select but before its fields should + be transformed with transformer_for_where to make it pushable. + + Otherwise the method checks wherever any condition depending only on + grouping fields can be extracted from cond. If there is any it prepares it + for pushing using grouping_field_transformer_for_where and if it happens to + be a conjunct of cond it removes it from cond. It saves the result of + removal in remaining_cond. + The extracted condition is saved in cond_pushed_into_where of this select. + + @note + When looking for pushable condition the method considers only the grouping + fields from the list grouping_tmp_fields whose elements are of the type + Field_pair. This list must be prepared before the call of the + function. + + @note + This method is called for pushdown conditions into materialized + derived tables/views optimization. + Item::derived_field_transformer_for_where is passed as the actual + callback function. + Also it is called for pushdown conditions into materialized IN subqueries. + Item::in_subq_field_transformer_for_where is passed as the actual + callback function. +*/ + +void st_select_lex::pushdown_cond_into_where_clause(THD *thd, Item *cond, + Item **remaining_cond, + Item_transformer transformer, + uchar *arg) +{ + if (!cond_pushdown_is_allowed()) + return; + thd->lex->current_select= this; + if (have_window_funcs()) + { + Item *cond_over_partition_fields; + check_cond_extraction_for_grouping_fields(cond); + cond_over_partition_fields= + build_cond_for_grouping_fields(thd, cond, true); + if (cond_over_partition_fields) + cond_over_partition_fields= cond_over_partition_fields->transform(thd, + &Item::grouping_field_transformer_for_where, + (uchar*) this); + if (cond_over_partition_fields) + { + cond_over_partition_fields->walk( + &Item::cleanup_excluding_const_fields_processor, 0, 0); + cond_pushed_into_where= cond_over_partition_fields; + } + + return; + } + + if (!join->group_list && !with_sum_func) + { + cond= + cond->transform(thd, transformer, arg); + if (cond) + { + cond->walk( + &Item::cleanup_excluding_const_fields_processor, 0, 0); + cond_pushed_into_where= cond; + } + + return; + } + + /* + Figure out what can be extracted from cond + that could be pushed into the WHERE clause of this select + */ + Item *cond_over_grouping_fields; + check_cond_extraction_for_grouping_fields(cond); + cond_over_grouping_fields= + build_cond_for_grouping_fields(thd, cond, true); + + /* + Transform the references to the columns from the cond + pushed into the WHERE clause of this select to make them usable in + the new context + */ + if (cond_over_grouping_fields) + cond_over_grouping_fields= cond_over_grouping_fields->transform(thd, + &Item::grouping_field_transformer_for_where, + (uchar*) this); + + if (cond_over_grouping_fields) + { + + /* + In cond remove top conjuncts that has been pushed into the WHERE + clause of this select + */ + cond= remove_pushed_top_conjuncts(thd, cond); + + cond_over_grouping_fields->walk( + &Item::cleanup_excluding_const_fields_processor, 0, 0); + cond_pushed_into_where= cond_over_grouping_fields; + } + + *remaining_cond= cond; +} |