diff options
Diffstat (limited to 'sql/sql_derived.cc')
| -rw-r--r-- | sql/sql_derived.cc | 211 |
1 files changed, 90 insertions, 121 deletions
diff --git a/sql/sql_derived.cc b/sql/sql_derived.cc index ab66384c6cb..2df740b6811 100644 --- a/sql/sql_derived.cc +++ b/sql/sql_derived.cc @@ -1242,25 +1242,61 @@ bool mysql_derived_reinit(THD *thd, LEX *lex, TABLE_LIST *derived) /** @brief - Extract the condition depended on derived table/view and pushed it there + Extract condition that can be pushed into a derived table/view - @param thd The thread handle - @param cond The condition from which to extract the pushed condition - @param derived The reference to the derived table/view + @param thd the thread handle + @param cond current condition + @param derived the reference to the derived table/view @details - This functiom builds the most restrictive condition depending only on - the derived table/view that can be extracted from the condition cond. - The built condition is pushed into the having clauses of the - selects contained in the query specifying the derived table/view. - The function also checks for each select whether any condition depending - only on grouping fields can be extracted from the pushed condition. - If so, it pushes the condition over grouping fields into the where - clause of the select. - - @retval - true if an error is reported - false otherwise + This function builds the most restrictive condition depending only on + the derived table/view (directly or indirectly through equality) that + can be extracted from the given condition cond and pushes it into the + derived table/view. + + Example of the transformation: + + SELECT * + FROM t1, + ( + SELECT x,MAX(y) AS max_y + FROM t2 + GROUP BY x + ) AS d_tab + WHERE d_tab.x>1 AND d_tab.max_y<30; + + => + + SELECT * + FROM t1, + ( + SELECT x,z,MAX(y) AS max_y + FROM t2 + WHERE x>1 + HAVING max_y<30 + GROUP BY x + ) AS d_tab + WHERE d_tab.x>1 AND d_tab.max_y<30; + + In details: + 1. Check what pushable formula can be extracted from cond + 2. Build a clone PC of the formula that can be extracted + (the clone is built only if the extracted formula is a AND subformula + of cond or conjunction of such subformulas) + Do for every select specifying derived table/view: + 3. If there is no HAVING clause prepare PC to be conjuncted with + WHERE clause of the select. Otherwise do 4-7. + 4. Check what formula PC_where can be extracted from PC to be pushed + into the WHERE clause of the select + 5. Build PC_where and if PC_where is a conjunct(s) of PC remove it from PC + getting PC_having + 6. Prepare PC_where to be conjuncted with the WHERE clause of the select + 7. Prepare PC_having to be conjuncted with the HAVING clause of the select + @note + This method is similar to pushdown_cond_for_in_subquery() + + @retval TRUE if an error occurs + @retval FALSE otherwise */ bool pushdown_cond_for_derived(THD *thd, Item *cond, TABLE_LIST *derived) @@ -1300,63 +1336,25 @@ bool pushdown_cond_for_derived(THD *thd, Item *cond, TABLE_LIST *derived) if (!some_select_allows_cond_pushdown) DBUG_RETURN(false); - /* - Build the most restrictive condition extractable from 'cond' - that can be pushed into the derived table 'derived'. - All subexpressions of this condition are cloned from the - subexpressions of 'cond'. - This condition has to be fixed yet. - */ + /* 1. Check what pushable formula can be extracted from cond */ Item *extracted_cond; - derived->check_pushable_cond_for_table(cond); - extracted_cond= derived->build_pushable_cond_for_table(thd, cond); + cond->check_pushable_cond(&Item::pushable_cond_checker_for_derived, + (uchar *)(&derived->table->map)); + /* 2. Build a clone PC of the formula that can be extracted */ + extracted_cond= + cond->build_pushable_cond(thd, + &Item::pushable_equality_checker_for_derived, + ((uchar *)&derived->table->map)); if (!extracted_cond) { /* Nothing can be pushed into the derived table */ DBUG_RETURN(false); } - /* Push extracted_cond into every select of the unit specifying 'derived' */ + st_select_lex *save_curr_select= thd->lex->current_select; for (; sl; sl= sl->next_select()) { Item *extracted_cond_copy; - if (!sl->cond_pushdown_is_allowed()) - continue; - thd->lex->current_select= sl; - if (sl->have_window_funcs()) - { - if (sl->join->group_list || sl->join->implicit_grouping) - continue; - ORDER *common_partition_fields= - sl->find_common_window_func_partition_fields(thd); - if (!common_partition_fields) - continue; - extracted_cond_copy= !sl->next_select() ? - extracted_cond : - extracted_cond->build_clone(thd); - if (!extracted_cond_copy) - continue; - - Item *cond_over_partition_fields;; - sl->collect_grouping_fields(thd, common_partition_fields); - sl->check_cond_extraction_for_grouping_fields(extracted_cond_copy, - derived); - cond_over_partition_fields= - sl->build_cond_for_grouping_fields(thd, extracted_cond_copy, true); - if (cond_over_partition_fields) - cond_over_partition_fields= cond_over_partition_fields->transform(thd, - &Item::derived_grouping_field_transformer_for_where, - (uchar*) sl); - if (cond_over_partition_fields) - { - cond_over_partition_fields->walk( - &Item::cleanup_excluding_const_fields_processor, 0, 0); - sl->cond_pushed_into_where= cond_over_partition_fields; - } - - continue; - } - /* For each select of the unit except the last one create a clone of extracted_cond @@ -1367,73 +1365,44 @@ bool pushdown_cond_for_derived(THD *thd, Item *cond, TABLE_LIST *derived) if (!extracted_cond_copy) continue; - if (!sl->join->group_list && !sl->with_sum_func) - { - /* extracted_cond_copy is pushed into where of sl */ - extracted_cond_copy= extracted_cond_copy->transform(thd, - &Item::derived_field_transformer_for_where, - (uchar*) sl); - if (extracted_cond_copy) - { - extracted_cond_copy->walk( - &Item::cleanup_excluding_const_fields_processor, 0, 0); - sl->cond_pushed_into_where= extracted_cond_copy; - } - - continue; - } - - /* - Figure out what can be extracted from the pushed condition - that could be pushed into the where clause of sl - */ - Item *cond_over_grouping_fields; - sl->collect_grouping_fields(thd, sl->join->group_list); - sl->check_cond_extraction_for_grouping_fields(extracted_cond_copy, - derived); - cond_over_grouping_fields= - sl->build_cond_for_grouping_fields(thd, extracted_cond_copy, true); - - /* - Transform the references to the 'derived' columns from the condition - pushed into the where clause of sl to make them usable in the new context - */ - if (cond_over_grouping_fields) - cond_over_grouping_fields= cond_over_grouping_fields->transform(thd, - &Item::derived_grouping_field_transformer_for_where, - (uchar*) sl); - - if (cond_over_grouping_fields) + /* Collect fields that are used in the GROUP BY of sl */ + if (sl->have_window_funcs()) { - /* - In extracted_cond_copy remove top conjuncts that - has been pushed into the where clause of sl - */ - extracted_cond_copy= remove_pushed_top_conjuncts(thd, extracted_cond_copy); - - cond_over_grouping_fields->walk( - &Item::cleanup_excluding_const_fields_processor, 0, 0); - sl->cond_pushed_into_where= cond_over_grouping_fields; - - if (!extracted_cond_copy) + if (sl->group_list.first || sl->join->implicit_grouping) + continue; + ORDER *common_partition_fields= + sl->find_common_window_func_partition_fields(thd); + if (!common_partition_fields) continue; + sl->collect_grouping_fields(thd, common_partition_fields); } + else + sl->collect_grouping_fields(thd, sl->group_list.first); + + Item *remaining_cond= NULL; + /* Do 4-6 */ + sl->pushdown_cond_into_where_clause(thd, extracted_cond_copy, + &remaining_cond, + &Item::derived_field_transformer_for_where, + (uchar *) sl); + if (!remaining_cond) + continue; /* - Transform the references to the 'derived' columns from the condition - pushed into the having clause of sl to make them usable in the new context + 7. Prepare PC_having to be conjuncted with the HAVING clause of + the select */ - extracted_cond_copy= extracted_cond_copy->transform(thd, - &Item::derived_field_transformer_for_having, - (uchar*) sl); - if (!extracted_cond_copy) + remaining_cond= + remaining_cond->transform(thd, + &Item::derived_field_transformer_for_having, + (uchar *) sl); + if (!remaining_cond) continue; - extracted_cond_copy->walk(&Item::cleanup_excluding_const_fields_processor, - 0, 0); - sl->cond_pushed_into_having= extracted_cond_copy; + remaining_cond->walk(&Item::cleanup_excluding_const_fields_processor, + 0, 0); + sl->cond_pushed_into_having= remaining_cond; } thd->lex->current_select= save_curr_select; DBUG_RETURN(false); } - |