/* Copyright (c) 2002, 2011, Oracle and/or its affiliates. Copyright (c) 2010, 2015, MariaDB 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; 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 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1335 USA */ /* Derived tables These were introduced by Sinisa */ #include /* NO_EMBEDDED_ACCESS_CHECKS */ #include "sql_priv.h" #include "unireg.h" #include "sql_derived.h" #include "sql_select.h" #include "sql_base.h" #include "sql_view.h" // check_duplicate_names #include "sql_acl.h" // SELECT_ACL #include "sql_class.h" #include "sql_cte.h" typedef bool (*dt_processor)(THD *thd, LEX *lex, TABLE_LIST *derived); bool mysql_derived_init(THD *thd, LEX *lex, TABLE_LIST *derived); bool mysql_derived_prepare(THD *thd, LEX *lex, TABLE_LIST *derived); bool mysql_derived_optimize(THD *thd, LEX *lex, TABLE_LIST *derived); bool mysql_derived_merge(THD *thd, LEX *lex, TABLE_LIST *derived); bool mysql_derived_create(THD *thd, LEX *lex, TABLE_LIST *derived); bool mysql_derived_fill(THD *thd, LEX *lex, TABLE_LIST *derived); bool mysql_derived_reinit(THD *thd, LEX *lex, TABLE_LIST *derived); bool mysql_derived_merge_for_insert(THD *thd, LEX *lex, TABLE_LIST *derived); dt_processor processors[]= { &mysql_derived_init, &mysql_derived_prepare, &mysql_derived_optimize, &mysql_derived_merge, &mysql_derived_merge_for_insert, &mysql_derived_create, &mysql_derived_fill, &mysql_derived_reinit, }; /* Run specified phases on all derived tables/views in given LEX. @param lex LEX for this thread @param phases phases to run derived tables/views through @return FALSE OK @return TRUE Error */ bool mysql_handle_derived(LEX *lex, uint phases) { bool res= FALSE; THD *thd= lex->thd; DBUG_ENTER("mysql_handle_derived"); DBUG_PRINT("enter", ("phases: 0x%x", phases)); if (!lex->derived_tables) DBUG_RETURN(FALSE); lex->thd->derived_tables_processing= TRUE; for (uint phase= 0; phase < DT_PHASES && !res; phase++) { uint phase_flag= DT_INIT << phase; if (phase_flag > phases) break; if (!(phases & phase_flag)) continue; if (phase_flag >= DT_CREATE && !thd->fill_derived_tables()) break; for (SELECT_LEX *sl= lex->all_selects_list; sl && !res; sl= sl->next_select_in_list()) { TABLE_LIST *cursor= sl->get_table_list(); sl->changed_elements|= TOUCHED_SEL_DERIVED; /* DT_MERGE_FOR_INSERT is not needed for views/derived tables inside subqueries. Views and derived tables of subqueries should be processed normally. */ if (phases == DT_MERGE_FOR_INSERT && cursor && cursor->top_table()->select_lex != &lex->select_lex) continue; for (; cursor && !res; cursor= cursor->next_local) { if (!cursor->is_view_or_derived() && phases == DT_MERGE_FOR_INSERT) continue; uint8 allowed_phases= (cursor->is_merged_derived() ? DT_PHASES_MERGE : DT_PHASES_MATERIALIZE | DT_MERGE_FOR_INSERT); /* Skip derived tables to which the phase isn't applicable. TODO: mark derived at the parse time, later set it's type (merged or materialized) */ if ((phase_flag != DT_PREPARE && !(allowed_phases & phase_flag)) || (cursor->merged_for_insert && phase_flag != DT_REINIT && phase_flag != DT_PREPARE)) continue; res= (*processors[phase])(lex->thd, lex, cursor); } if (lex->describe) { /* Force join->join_tmp creation, because we will use this JOIN twice for EXPLAIN and we have to have unchanged join for EXPLAINing */ sl->uncacheable|= UNCACHEABLE_EXPLAIN; sl->master_unit()->uncacheable|= UNCACHEABLE_EXPLAIN; } } } lex->thd->derived_tables_processing= FALSE; DBUG_RETURN(res); } /* Run through phases for the given derived table/view. @param lex LEX for this thread @param derived the derived table to handle @param phase_map phases to process tables/views through @details This function process the derived table (view) 'derived' to performs all actions that are to be done on the table at the phases specified by phase_map. The processing is carried out starting from the actions performed at the earlier phases (those having smaller ordinal numbers). @note This function runs specified phases of the derived tables handling on the given derived table/view. This function is used in the chain of calls: SELECT_LEX::handle_derived -> TABLE_LIST::handle_derived -> mysql_handle_single_derived This chain of calls implements the bottom-up handling of the derived tables: i.e. most inner derived tables/views are handled first. This order is required for the all phases except the merge and the create steps. For the sake of code simplicity this order is kept for all phases. @return FALSE ok @return TRUE error */ bool mysql_handle_single_derived(LEX *lex, TABLE_LIST *derived, uint phases) { bool res= FALSE; THD *thd= lex->thd; uint8 allowed_phases= (derived->is_merged_derived() ? DT_PHASES_MERGE : DT_PHASES_MATERIALIZE); DBUG_ENTER("mysql_handle_single_derived"); DBUG_PRINT("enter", ("phases: 0x%x allowed: 0x%x alias: '%s'", phases, allowed_phases, (derived->alias ? derived->alias : ""))); if (!lex->derived_tables) DBUG_RETURN(FALSE); lex->thd->derived_tables_processing= TRUE; for (uint phase= 0; phase < DT_PHASES; phase++) { uint phase_flag= DT_INIT << phase; if (phase_flag > phases) break; if (!(phases & phase_flag)) continue; /* Skip derived tables to which the phase isn't applicable. */ if (phase_flag != DT_PREPARE && !(allowed_phases & phase_flag)) continue; if (phase_flag >= DT_CREATE && !thd->fill_derived_tables()) break; if ((res= (*processors[phase])(lex->thd, lex, derived))) break; } lex->thd->derived_tables_processing= FALSE; DBUG_RETURN(res); } /** Merge a derived table/view into the embedding select @param thd thread handle @param lex LEX of the embedding query. @param derived reference to the derived table. @details This function merges the given derived table / view into the parent select construction. Any derived table/reference to view occurred in the FROM clause of the embedding select is represented by a TABLE_LIST structure a pointer to which is passed to the function as in the parameter 'derived'. This structure contains the number/map, alias, a link to SELECT_LEX of the derived table and other info. If the 'derived' table is used in a nested join then additionally the structure contains a reference to the ON expression for this join. The merge process results in elimination of the derived table (or the reference to a view) such that: - the FROM list of the derived table/view is wrapped into a nested join after which the nest is added to the FROM list of the embedding select - the WHERE condition of the derived table (view) is ANDed with the ON condition attached to the table. @note Tables are merged into the leaf_tables list, original derived table is removed from this list also. SELECT_LEX::table_list list is left untouched. Where expression is merged with derived table's on_expr and can be found after the merge through the SELECT_LEX::table_list. Examples of the derived table/view merge: Schema: Tables: t1(f1), t2(f2), t3(f3) View v1: SELECT f1 FROM t1 WHERE f1 < 1 Example with a view: Before merge: The query (Q1): SELECT f1,f2 FROM t2 LEFT JOIN v1 ON f1 = f2 (LEX of the main query) | (select_lex) | (FROM table list) | (join list)= t2, v1 / \ / (on_expr)= (f1 = f2) | (LEX of the v1 view) | (select_lex)= SELECT f1 FROM t1 WHERE f1 < 1 After merge: The rewritten query Q1 (Q1'): SELECT f1,f2 FROM t2 LEFT JOIN (t1) ON ((f1 = f2) and (f1 < 1)) (LEX of the main query) | (select_lex) | (FROM table list) | (join list)= t2, (t1) \ (on_expr)= (f1 = f2) and (f1 < 1) In this example table numbers are assigned as follows: (outer select): t2 - 1, v1 - 2 (inner select): t1 - 1 After the merge table numbers will be: (outer select): t2 - 1, t1 - 2 Example with a derived table: The query Q2: SELECT f1,f2 FROM (SELECT f1 FROM t1, t3 WHERE f1=f3 and f1 < 1) tt, t2 WHERE f1 = f2 Before merge: (LEX of the main query) | (select_lex) / \ (FROM table list) (WHERE clause)= (f1 = f2) | (join list)= tt, t2 / \ / (on_expr)= (empty) / (select_lex)= SELECT f1 FROM t1, t3 WHERE f1 = f3 and f1 < 1 After merge: The rewritten query Q2 (Q2'): SELECT f1,f2 FROM (t1, t3) JOIN t2 ON (f1 = f3 and f1 < 1) WHERE f1 = f2 (LEX of the main query) | (select_lex) / \ (FROM table list) (WHERE clause)= (f1 = f2) | (join list)= t2, (t1, t3) \ (on_expr)= (f1 = f3 and f1 < 1) In this example table numbers are assigned as follows: (outer select): tt - 1, t2 - 2 (inner select): t1 - 1, t3 - 2 After the merge table numbers will be: (outer select): t1 - 1, t2 - 2, t3 - 3 @return FALSE if derived table/view were successfully merged. @return TRUE if an error occur. */ bool mysql_derived_merge(THD *thd, LEX *lex, TABLE_LIST *derived) { bool res= FALSE; SELECT_LEX *dt_select= derived->get_single_select(); table_map map; uint tablenr; SELECT_LEX *parent_lex= derived->select_lex; Query_arena *arena, backup; DBUG_ENTER("mysql_derived_merge"); DBUG_PRINT("enter", ("Alias: '%s' Unit: %p", (derived->alias ? derived->alias : ""), derived->get_unit())); if (derived->merged) { DBUG_PRINT("info", ("Irreversibly merged: exit")); DBUG_RETURN(FALSE); } if (dt_select->uncacheable & UNCACHEABLE_RAND) { /* There is random function => fall back to materialization. */ derived->change_refs_to_fields(); derived->set_materialized_derived(); DBUG_RETURN(FALSE); } if (thd->lex->sql_command == SQLCOM_UPDATE_MULTI || thd->lex->sql_command == SQLCOM_DELETE_MULTI) thd->save_prep_leaf_list= TRUE; arena= thd->activate_stmt_arena_if_needed(&backup); // For easier test if (!derived->merged_for_insert || (derived->is_multitable() && (thd->lex->sql_command == SQLCOM_UPDATE_MULTI || thd->lex->sql_command == SQLCOM_DELETE_MULTI))) { /* Check whether there is enough free bits in table map to merge subquery. If not - materialize it. This check isn't cached so when there is a big and small subqueries, and the bigger one can't be merged it wouldn't block the smaller one. */ if (parent_lex->get_free_table_map(&map, &tablenr)) { /* There is no enough table bits, fall back to materialization. */ goto unconditional_materialization; } if (dt_select->leaf_tables.elements + tablenr > MAX_TABLES) { /* There is no enough table bits, fall back to materialization. */ goto unconditional_materialization; } if (dt_select->options & OPTION_SCHEMA_TABLE) parent_lex->options |= OPTION_SCHEMA_TABLE; if (!derived->get_unit()->prepared) { dt_select->leaf_tables.empty(); make_leaves_list(thd, dt_select->leaf_tables, derived, TRUE, 0); } derived->nested_join= (NESTED_JOIN*) thd->calloc(sizeof(NESTED_JOIN)); if (!derived->nested_join) { res= TRUE; goto exit_merge; } /* Merge derived table's subquery in the parent select. */ if (parent_lex->merge_subquery(thd, derived, dt_select, tablenr, map)) { res= TRUE; goto exit_merge; } /* exclude select lex so it doesn't show up in explain. do this only for derived table as for views this is already done. From sql_view.cc Add subqueries units to SELECT into which we merging current view. unit(->next)* chain starts with subqueries that are used by this view and continues with subqueries that are used by other views. We must not add any subquery twice (otherwise we'll form a loop), to do this we remember in end_unit the first subquery that has been already added. */ derived->get_unit()->exclude_level(); if (parent_lex->join) parent_lex->join->table_count+= dt_select->join->table_count - 1; } derived->merged= TRUE; if (derived->get_unit()->prepared) { Item *expr= derived->on_expr; expr= and_conds(thd, expr, dt_select->join ? dt_select->join->conds : 0); if (expr) expr->top_level_item(); if (expr && (derived->prep_on_expr || expr != derived->on_expr)) { derived->on_expr= expr; derived->prep_on_expr= expr->copy_andor_structure(thd); } if (derived->on_expr && ((!derived->on_expr->fixed && derived->on_expr->fix_fields(thd, &derived->on_expr)) || derived->on_expr->check_cols(1))) { res= TRUE; /* purecov: inspected */ goto exit_merge; } // Update used tables cache according to new table map if (derived->on_expr) { derived->on_expr->fix_after_pullout(parent_lex, &derived->on_expr, TRUE); fix_list_after_tbl_changes(parent_lex, &derived->nested_join->join_list); } } exit_merge: if (arena) thd->restore_active_arena(arena, &backup); DBUG_RETURN(res); unconditional_materialization: derived->change_refs_to_fields(); derived->set_materialized_derived(); if (!derived->table || !derived->table->is_created()) res= mysql_derived_create(thd, lex, derived); goto exit_merge; } /** Merge a view for the embedding INSERT/UPDATE/DELETE @param thd thread handle @param lex LEX of the embedding query. @param derived reference to the derived table. @details This function substitutes the derived table for the first table from the query of the derived table thus making it a correct target table for the INSERT/UPDATE/DELETE statements. As this operation is correct only for single table views only, for multi table views this function does nothing. The derived parameter isn't checked to be a view as derived tables aren't allowed for INSERT/UPDATE/DELETE statements. @return FALSE if derived table/view were successfully merged. @return TRUE if an error occur. */ bool mysql_derived_merge_for_insert(THD *thd, LEX *lex, TABLE_LIST *derived) { DBUG_ENTER("mysql_derived_merge_for_insert"); DBUG_PRINT("enter", ("Alias: '%s' Unit: %p", (derived->alias ? derived->alias : ""), derived->get_unit())); DBUG_PRINT("info", ("merged_for_insert: %d is_materialized_derived: %d " "is_multitable: %d single_table_updatable: %d " "merge_underlying_list: %d", derived->merged_for_insert, derived->is_materialized_derived(), derived->is_multitable(), derived->single_table_updatable(), derived->merge_underlying_list != 0)); if (derived->merged_for_insert) DBUG_RETURN(FALSE); if (derived->init_derived(thd, FALSE)) DBUG_RETURN(TRUE); if (derived->is_materialized_derived()) DBUG_RETURN(mysql_derived_prepare(thd, lex, derived)); if ((thd->lex->sql_command == SQLCOM_UPDATE_MULTI || thd->lex->sql_command == SQLCOM_DELETE_MULTI)) DBUG_RETURN(FALSE); if (!derived->is_multitable()) { if (!derived->single_table_updatable()) DBUG_RETURN(derived->create_field_translation(thd)); if (derived->merge_underlying_list) { derived->table= derived->merge_underlying_list->table; derived->schema_table= derived->merge_underlying_list->schema_table; derived->merged_for_insert= TRUE; DBUG_ASSERT(derived->table); } } DBUG_RETURN(FALSE); } /* Initialize a derived table/view @param thd Thread handle @param lex LEX of the embedding query. @param derived reference to the derived table. @detail Fill info about derived table/view without preparing an underlying select. Such as: create a field translation for views, mark it as a multitable if it is and so on. @return false OK true Error */ bool mysql_derived_init(THD *thd, LEX *lex, TABLE_LIST *derived) { SELECT_LEX_UNIT *unit= derived->get_unit(); DBUG_ENTER("mysql_derived_init"); DBUG_PRINT("enter", ("Alias: '%s' Unit: %p", (derived->alias ? derived->alias : ""), derived->get_unit())); // Skip already prepared views/DT if (!unit || unit->prepared) DBUG_RETURN(FALSE); bool res= derived->init_derived(thd, TRUE); derived->updatable= derived->updatable && derived->is_view(); DBUG_RETURN(res); } /* Create temporary table structure (but do not fill it) @param thd Thread handle @param lex LEX of the embedding query. @param derived reference to the derived table. @detail Prepare underlying select for a derived table/view. To properly resolve names in the embedding query the TABLE structure is created. Actual table is created later by the mysql_derived_create function. This function is called before any command containing derived table is executed. All types of derived tables are handled by this function: - Anonymous derived tables, or - Named derived tables (aka views). The table reference, contained in @c derived, is updated with the fields of a new temporary table. Derived tables are stored in @c thd->derived_tables and closed by close_thread_tables(). This function is part of the procedure that starts in open_and_lock_tables(), a procedure that - among other things - introduces new table and table reference objects (to represent derived tables) that don't exist in the privilege database. This means that normal privilege checking cannot handle them. Hence this function does some extra tricks in order to bypass normal privilege checking, by exploiting the fact that the current state of privilege verification is attached as GRANT_INFO structures on the relevant TABLE and TABLE_REF objects. For table references, the current state of accrued access is stored inside TABLE_LIST::grant. Hence this function must update the state of fulfilled privileges for the new TABLE_LIST, an operation which is normally performed exclusively by the table and database access checking functions, check_access() and check_grant(), respectively. This modification is done for both views and anonymous derived tables: The @c SELECT privilege is set as fulfilled by the user. However, if a view is referenced and the table reference is queried against directly (see TABLE_LIST::referencing_view), the state of privilege checking (GRANT_INFO struct) is copied as-is to the temporary table. Only the TABLE structure is created here, actual table is created by the mysql_derived_create function. @note This function sets @c SELECT_ACL for @c TEMPTABLE views as well as anonymous derived tables, but this is ok since later access checking will distinguish between them. @see mysql_handle_derived(), mysql_derived_fill(), GRANT_INFO @return false OK true Error */ bool mysql_derived_prepare(THD *thd, LEX *lex, TABLE_LIST *derived) { SELECT_LEX_UNIT *unit= derived->get_unit(); DBUG_ENTER("mysql_derived_prepare"); bool res= FALSE; DBUG_PRINT("enter", ("Alias: '%s' Unit: %p", (derived->alias ? derived->alias : ""), unit)); if (!unit) DBUG_RETURN(FALSE); SELECT_LEX *first_select= unit->first_select(); if (derived->is_recursive_with_table() && !derived->is_with_table_recursive_reference() && !derived->with->rec_result && derived->with->get_sq_rec_ref()) { /* This is a non-recursive reference to a recursive CTE whose specification unit has not been prepared at the regular processing of derived table references. This can happen only in the case when the specification unit has no recursive references at the top level. Force the preparation of the specification unit. Use a recursive table reference from a subquery for this. */ DBUG_ASSERT(derived->with->get_sq_rec_ref()); if (mysql_derived_prepare(lex->thd, lex, derived->with->get_sq_rec_ref())) DBUG_RETURN(TRUE); } if (unit->prepared && derived->is_recursive_with_table() && !derived->table) { /* Here 'derived' is either a non-recursive table reference to a recursive with table or a recursive table reference to a recursvive table whose specification has been already prepared (a secondary recursive table reference. */ if (!(derived->derived_result= new (thd->mem_root) select_union(thd))) DBUG_RETURN(TRUE); // out of memory thd->create_tmp_table_for_derived= TRUE; res= derived->derived_result->create_result_table( thd, &unit->types, FALSE, (first_select->options | thd->variables.option_bits | TMP_TABLE_ALL_COLUMNS), derived->alias, FALSE, FALSE); thd->create_tmp_table_for_derived= FALSE; if (!res && !derived->table) { derived->derived_result->set_unit(unit); derived->table= derived->derived_result->table; if (derived->is_with_table_recursive_reference()) { /* Here 'derived" is a secondary recursive table reference */ unit->with_element->rec_result->rec_table_refs.push_back(derived); } } DBUG_ASSERT(derived->table || res); goto exit; } // Skip already prepared views/DT if (unit->prepared || (derived->merged_for_insert && !(derived->is_multitable() && (thd->lex->sql_command == SQLCOM_UPDATE_MULTI || thd->lex->sql_command == SQLCOM_DELETE_MULTI)))) DBUG_RETURN(FALSE); /* prevent name resolving out of derived table */ for (SELECT_LEX *sl= first_select; sl; sl= sl->next_select()) { sl->context.outer_context= 0; if (!derived->is_with_table_recursive_reference() || (!derived->with->with_anchor && !derived->with->is_with_prepared_anchor())) { /* Prepare underlying views/DT first unless 'derived' is a recursive table reference and either the anchors from the specification of 'derived' has been already prepared or there no anchor in this specification */ if ((res= sl->handle_derived(lex, DT_PREPARE))) goto exit; } if (derived->outer_join && sl->first_cond_optimization) { /* Mark that table is part of OUTER JOIN and fields may be NULL */ for (TABLE_LIST *cursor= (TABLE_LIST*) sl->table_list.first; cursor; cursor= cursor->next_local) cursor->outer_join|= JOIN_TYPE_OUTER; } } unit->derived= derived; /* Above cascade call of prepare is important for PS protocol, but after it is called we can check if we really need prepare for this derived */ if (derived->merged) { DBUG_PRINT("info", ("Irreversibly merged: exit")); DBUG_RETURN(FALSE); } derived->fill_me= FALSE; if ((!derived->is_with_table_recursive_reference() || !derived->derived_result) && !(derived->derived_result= new (thd->mem_root) select_union(thd))) DBUG_RETURN(TRUE); // out of memory // st_select_lex_unit::prepare correctly work for single select if ((res= unit->prepare(thd, derived->derived_result, 0))) goto exit; if (derived->with && (res= derived->with->rename_columns_of_derived_unit(thd, unit))) goto exit; if ((res= check_duplicate_names(thd, unit->types, 0))) goto exit; /* Check whether we can merge this derived table into main select. Depending on the result field translation will or will not be created. */ if (!derived->is_with_table_recursive_reference() && derived->init_derived(thd, FALSE)) goto exit; /* Temp table is created so that it hounours if UNION without ALL is to be processed As 'distinct' parameter we always pass FALSE (0), because underlying query will control distinct condition by itself. Correct test of distinct underlying query will be is_union && !unit->union_distinct->next_select() (i.e. it is union and last distinct SELECT is last SELECT of UNION). */ thd->create_tmp_table_for_derived= TRUE; if (!(derived->table) && derived->derived_result->create_result_table(thd, &unit->types, FALSE, (first_select->options | thd->variables.option_bits | TMP_TABLE_ALL_COLUMNS), derived->alias, FALSE, FALSE, FALSE)) { thd->create_tmp_table_for_derived= FALSE; goto exit; } thd->create_tmp_table_for_derived= FALSE; if (!derived->table) derived->table= derived->derived_result->table; DBUG_ASSERT(derived->table); if (derived->is_derived() && derived->is_merged_derived()) first_select->mark_as_belong_to_derived(derived); exit: /* Hide "Unknown column" or "Unknown function" error */ if (derived->view) { if (thd->is_error() && (thd->get_stmt_da()->sql_errno() == ER_BAD_FIELD_ERROR || thd->get_stmt_da()->sql_errno() == ER_FUNC_INEXISTENT_NAME_COLLISION || thd->get_stmt_da()->sql_errno() == ER_SP_DOES_NOT_EXIST)) { thd->clear_error(); my_error(ER_VIEW_INVALID, MYF(0), derived->db, derived->table_name); } } /* if it is preparation PS only or commands that need only VIEW structure then we do not need real data and we can skip execution (and parameters is not defined, too) */ if (res) { if (!derived->is_with_table_recursive_reference()) { if (derived->table) free_tmp_table(thd, derived->table); delete derived->derived_result; } } else { TABLE *table= derived->table; table->derived_select_number= first_select->select_number; table->s->tmp_table= INTERNAL_TMP_TABLE; #ifndef NO_EMBEDDED_ACCESS_CHECKS if (derived->is_view()) table->grant= derived->grant; else { DBUG_ASSERT(derived->is_derived()); DBUG_ASSERT(derived->is_anonymous_derived_table()); table->grant.privilege= SELECT_ACL; derived->grant.privilege= SELECT_ACL; } #endif /* Add new temporary table to list of open derived tables */ if (!derived->is_with_table_recursive_reference()) { table->next= thd->derived_tables; thd->derived_tables= table; } /* If table is used by a left join, mark that any column may be null */ if (derived->outer_join) table->maybe_null= 1; } DBUG_RETURN(res); } /** Runs optimize phase for a derived table/view. @param thd thread handle @param lex LEX of the embedding query. @param derived reference to the derived table. @details Runs optimize phase for given 'derived' derived table/view. If optimizer finds out that it's of the type "SELECT a_constant" then this functions also materializes it. @return FALSE ok. @return TRUE if an error occur. */ bool mysql_derived_optimize(THD *thd, LEX *lex, TABLE_LIST *derived) { SELECT_LEX_UNIT *unit= derived->get_unit(); SELECT_LEX *first_select= unit->first_select(); SELECT_LEX *save_current_select= lex->current_select; bool res= FALSE; DBUG_ENTER("mysql_derived_optimize"); DBUG_PRINT("enter", ("Alias: '%s' Unit: %p", (derived->alias ? derived->alias : ""), derived->get_unit())); if (derived->merged) { DBUG_PRINT("info", ("Irreversibly merged: exit")); DBUG_RETURN(FALSE); } if (unit->optimized) DBUG_RETURN(FALSE); lex->current_select= first_select; if (unit->is_union()) { // optimize union without execution res= unit->optimize(); } else if (unit->derived) { if (!derived->is_merged_derived()) { JOIN *join= first_select->join; unit->set_limit(unit->global_parameters()); unit->optimized= TRUE; if ((res= join->optimize())) goto err; if (join->table_count == join->const_tables) derived->fill_me= TRUE; } } /* Materialize derived tables/views of the "SELECT a_constant" type. Such tables should be materialized at the optimization phase for correct constant evaluation. */ if (!res && derived->fill_me && !derived->merged_for_insert) { if (derived->is_merged_derived()) { derived->change_refs_to_fields(); derived->set_materialized_derived(); } if ((res= mysql_derived_create(thd, lex, derived))) goto err; if ((res= mysql_derived_fill(thd, lex, derived))) goto err; } err: lex->current_select= save_current_select; DBUG_RETURN(res); } /** Actually create result table for a materialized derived table/view. @param thd thread handle @param lex LEX of the embedding query. @param derived reference to the derived table. @details This function actually creates the result table for given 'derived' table/view, but it doesn't fill it. 'thd' and 'lex' parameters are not used by this function. @return FALSE ok. @return TRUE if an error occur. */ bool mysql_derived_create(THD *thd, LEX *lex, TABLE_LIST *derived) { DBUG_ENTER("mysql_derived_create"); DBUG_PRINT("enter", ("Alias: '%s' Unit: %p", (derived->alias ? derived->alias : ""), derived->get_unit())); TABLE *table= derived->table; SELECT_LEX_UNIT *unit= derived->get_unit(); if (table->is_created()) DBUG_RETURN(FALSE); select_union *result= derived->derived_result; if (table->s->db_type() == TMP_ENGINE_HTON) { result->tmp_table_param.keyinfo= table->s->key_info; if (create_internal_tmp_table(table, result->tmp_table_param.keyinfo, result->tmp_table_param.start_recinfo, &result->tmp_table_param.recinfo, (unit->first_select()->options | thd->variables.option_bits | TMP_TABLE_ALL_COLUMNS))) DBUG_RETURN(TRUE); } if (open_tmp_table(table)) DBUG_RETURN(TRUE); table->file->extra(HA_EXTRA_WRITE_CACHE); table->file->extra(HA_EXTRA_IGNORE_DUP_KEY); DBUG_RETURN(FALSE); } /** @brief Fill the recursive with table @param thd The thread handle @details The method is called only for recursive with tables. The method executes the recursive part of the specification of this with table until no more rows are added to the table or the number of the performed iteration reaches the allowed maximum. @retval false on success true on failure */ bool TABLE_LIST::fill_recursive(THD *thd) { bool rc= false; st_select_lex_unit *unit= get_unit(); rc= with->instantiate_tmp_tables(); while (!rc && !with->all_are_stabilized()) { if (with->level > thd->variables.max_recursive_iterations) break; with->prepare_for_next_iteration(); rc= unit->exec_recursive(); } if (!rc) { TABLE *src= with->rec_result->table; rc =src->insert_all_rows_into_tmp_table(thd, table, &with->rec_result->tmp_table_param, true); } return rc; } /* Execute subquery of a materialized derived table/view and fill the result table. @param thd Thread handle @param lex LEX for this thread @param derived reference to the derived table. @details Execute subquery of given 'derived' table/view and fill the result table. After result table is filled, if this is not the EXPLAIN statement and the table is not specified with a recursion the entire unit / node is deleted. unit is deleted if UNION is used for derived table and node is deleted is it is a simple SELECT. 'lex' is unused and 'thd' is passed as an argument to an underlying function. @note If you use this function, make sure it's not called at prepare. Due to evaluation of LIMIT clause it can not be used at prepared stage. @return FALSE OK @return TRUE Error */ bool mysql_derived_fill(THD *thd, LEX *lex, TABLE_LIST *derived) { Field_iterator_table field_iterator; SELECT_LEX_UNIT *unit= derived->get_unit(); bool derived_is_recursive= derived->is_recursive_with_table(); bool res= FALSE; DBUG_ENTER("mysql_derived_fill"); DBUG_PRINT("enter", ("Alias: '%s' Unit: %p", (derived->alias ? derived->alias : ""), derived->get_unit())); if (unit->executed && !unit->uncacheable && !unit->describe && !derived_is_recursive) DBUG_RETURN(FALSE); /*check that table creation passed without problems. */ DBUG_ASSERT(derived->table && derived->table->is_created()); select_union *derived_result= derived->derived_result; SELECT_LEX *save_current_select= lex->current_select; if (derived_is_recursive) { if (derived->is_with_table_recursive_reference()) { /* Here only one iteration step is performed */ res= unit->exec_recursive(); } else { /* In this case all iteration are performed */ res= derived->fill_recursive(thd); } } else if (unit->is_union()) { // execute union without clean up res= unit->exec(); } else { SELECT_LEX *first_select= unit->first_select(); unit->set_limit(unit->global_parameters()); if (unit->select_limit_cnt == HA_POS_ERROR) first_select->options&= ~OPTION_FOUND_ROWS; lex->current_select= first_select; res= mysql_select(thd, first_select->table_list.first, first_select->with_wild, first_select->item_list, first_select->where, (first_select->order_list.elements+ first_select->group_list.elements), first_select->order_list.first, first_select->group_list.first, first_select->having, (ORDER*) NULL, (first_select->options |thd->variables.option_bits | SELECT_NO_UNLOCK), derived_result, unit, first_select); } if (!res && !derived_is_recursive) { if (derived_result->flush()) res= TRUE; unit->executed= TRUE; if (derived->field_translation) { /* reset translation table to materialized table */ field_iterator.set_table(derived->table); for (uint i= 0; !field_iterator.end_of_fields(); field_iterator.next(), i= i + 1) { Item *item; if (!(item= field_iterator.create_item(thd))) { res= TRUE; break; } thd->change_item_tree(&derived->field_translation[i].item, item); } } } if (res || (!lex->describe && !derived_is_recursive)) unit->cleanup(); lex->current_select= save_current_select; DBUG_RETURN(res); } /** Re-initialize given derived table/view for the next execution. @param thd thread handle @param lex LEX for this thread @param derived reference to the derived table. @details Re-initialize given 'derived' table/view for the next execution. All underlying views/derived tables are recursively reinitialized prior to re-initialization of given derived table. 'thd' and 'lex' are passed as arguments to called functions. @return FALSE OK @return TRUE Error */ bool mysql_derived_reinit(THD *thd, LEX *lex, TABLE_LIST *derived) { DBUG_ENTER("mysql_derived_reinit"); DBUG_PRINT("enter", ("Alias: '%s' Unit: %p", (derived->alias ? derived->alias : ""), derived->get_unit())); st_select_lex_unit *unit= derived->get_unit(); derived->merged_for_insert= FALSE; unit->unclean(); unit->types.empty(); /* for derived tables & PS (which can't be reset by Item_subselect) */ unit->reinit_exec_mechanism(); for (st_select_lex *sl= unit->first_select(); sl; sl= sl->next_select()) { sl->cond_pushed_into_where= NULL; sl->cond_pushed_into_having= NULL; } unit->set_thd(thd); DBUG_RETURN(FALSE); } /** @brief Extract the condition depended on derived table/view and pushed it there @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 @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 */ bool pushdown_cond_for_derived(THD *thd, Item *cond, TABLE_LIST *derived) { DBUG_ENTER("pushdown_cond_for_derived"); if (!cond) DBUG_RETURN(false); st_select_lex_unit *unit= derived->get_unit(); st_select_lex *first_sl= unit->first_select(); st_select_lex *sl= first_sl; if (derived->prohibit_cond_pushdown) DBUG_RETURN(false); /* Do not push conditions into constant derived */ if (unit->executed) DBUG_RETURN(false); /* Do not push conditions into recursive with tables */ if (derived->is_recursive_with_table()) DBUG_RETURN(false); /* Do not push conditions into unit with global ORDER BY ... LIMIT */ if (unit->fake_select_lex && unit->fake_select_lex->explicit_limit) DBUG_RETURN(false); /* Check whether any select of 'unit' allows condition pushdown */ bool some_select_allows_cond_pushdown= false; for (; sl; sl= sl->next_select()) { if (sl->cond_pushdown_is_allowed()) { some_select_allows_cond_pushdown= true; break; } } 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. */ Item *extracted_cond; derived->check_pushable_cond_for_table(cond); extracted_cond= derived->build_pushable_cond_for_table(thd, cond); 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()) { if (!sl->cond_pushdown_is_allowed()) continue; thd->lex->current_select= sl; /* For each select of the unit except the last one create a clone of extracted_cond */ Item *extracted_cond_copy= !sl->next_select() ? extracted_cond : extracted_cond->build_clone(thd, thd->mem_root); 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->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) { /* 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) continue; } /* Rename the columns of all non-first selects of a union to be compatible by names with the columns of the first select. It will allow to use copies of the same expression pushed into having clauses of different selects. */ if (sl != first_sl) { DBUG_ASSERT(sl->item_list.elements == first_sl->item_list.elements); List_iterator_fast it(sl->item_list); List_iterator_fast nm_it(unit->types); Item * item; while((item= it++)) { item->share_name_with(nm_it++); } } /* 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 */ extracted_cond_copy= extracted_cond_copy->transform(thd, &Item::derived_field_transformer_for_having, (uchar*) sl); if (!extracted_cond_copy) continue; extracted_cond_copy->walk(&Item::cleanup_excluding_const_fields_processor, 0, 0); sl->cond_pushed_into_having= extracted_cond_copy; } thd->lex->current_select= save_curr_select; DBUG_RETURN(false); }