/* Copyright (C) 2002-2003 MySQL AB 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */ /* Derived tables These were introduced by Sinisa <sinisa@mysql.com> */ #include "mysql_priv.h" #include "sql_select.h" /* Call given derived table processor (preparing or filling tables) SYNOPSIS mysql_handle_derived() lex LEX for this thread processor procedure of derived table processing RETURN FALSE OK TRUE Error */ bool mysql_handle_derived(LEX *lex, bool (*processor)(THD*, LEX*, TABLE_LIST*)) { bool res= FALSE; if (lex->derived_tables) { lex->thd->derived_tables_processing= TRUE; for (SELECT_LEX *sl= lex->all_selects_list; sl; sl= sl->next_select_in_list()) { for (TABLE_LIST *cursor= sl->get_table_list(); cursor; cursor= cursor->next_local) { if ((res= (*processor)(lex->thd, lex, cursor))) goto out; } 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; } } } out: lex->thd->derived_tables_processing= FALSE; return res; } /** @brief Create temporary table structure (but do not fill it). @param thd Thread handle @param lex LEX for this thread @param orig_table_list TABLE_LIST for the upper SELECT @details This function is called before any command containing derived tables is executed. Currently the function is used for derived tables, i.e. - Anonymous derived tables, or - Named derived tables (aka views) with the @c TEMPTABLE algorithm. The table reference, contained in @c orig_table_list, 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. This function implements a signature called "derived table processor", and is passed as a function pointer to mysql_handle_derived(). @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_filling(), GRANT_INFO @return false OK true Error */ bool mysql_derived_prepare(THD *thd, LEX *lex, TABLE_LIST *orig_table_list) { SELECT_LEX_UNIT *unit= orig_table_list->derived; ulonglong create_options; DBUG_ENTER("mysql_derived_prepare"); bool res= FALSE; if (unit) { SELECT_LEX *first_select= unit->first_select(); TABLE *table= 0; select_union *derived_result; /* 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_result= new select_union)) DBUG_RETURN(TRUE); // out of memory // st_select_lex_unit::prepare correctly work for single select if ((res= unit->prepare(thd, derived_result, 0))) goto exit; if ((res= check_duplicate_names(unit->types, 0))) goto exit; create_options= (first_select->options | thd->options | TMP_TABLE_ALL_COLUMNS); /* 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). */ if ((res= derived_result->create_result_table(thd, &unit->types, FALSE, create_options, orig_table_list->alias))) goto exit; table= derived_result->table; exit: /* Hide "Unknown column" or "Unknown function" error */ if (orig_table_list->view) { if (thd->is_error() && (thd->stmt_da->sql_errno() == ER_BAD_FIELD_ERROR || thd->stmt_da->sql_errno() == ER_FUNC_INEXISTENT_NAME_COLLISION || thd->stmt_da->sql_errno() == ER_SP_DOES_NOT_EXIST)) { thd->clear_error(); my_error(ER_VIEW_INVALID, MYF(0), orig_table_list->db, orig_table_list->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 (table) free_tmp_table(thd, table); delete derived_result; } else { if (!thd->fill_derived_tables()) { delete derived_result; derived_result= NULL; } orig_table_list->derived_result= derived_result; orig_table_list->table= table; orig_table_list->table_name= table->s->table_name.str; orig_table_list->table_name_length= table->s->table_name.length; table->derived_select_number= first_select->select_number; table->s->tmp_table= NON_TRANSACTIONAL_TMP_TABLE; #ifndef NO_EMBEDDED_ACCESS_CHECKS if (orig_table_list->referencing_view) table->grant= orig_table_list->grant; else table->grant.privilege= SELECT_ACL; #endif orig_table_list->db= (char *)""; orig_table_list->db_length= 0; // Force read of table stats in the optimizer table->file->info(HA_STATUS_VARIABLE); /* Add new temporary table to list of open derived tables */ table->next= thd->derived_tables; thd->derived_tables= table; } } else if (orig_table_list->merge_underlying_list) orig_table_list->set_underlying_merge(); DBUG_RETURN(res); } /* fill derived table SYNOPSIS mysql_derived_filling() thd Thread handle lex LEX for this thread unit node that contains all SELECT's for derived tables orig_table_list TABLE_LIST for the upper SELECT IMPLEMENTATION Derived table is resolved with temporary table. It is created based on the queries defined. After temporary table is filled, if this is not EXPLAIN, then 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. 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 TRUE Error */ bool mysql_derived_filling(THD *thd, LEX *lex, TABLE_LIST *orig_table_list) { TABLE *table= orig_table_list->table; SELECT_LEX_UNIT *unit= orig_table_list->derived; bool res= FALSE; /*check that table creation pass without problem and it is derived table */ if (table && unit) { SELECT_LEX *first_select= unit->first_select(); select_union *derived_result= orig_table_list->derived_result; SELECT_LEX *save_current_select= lex->current_select; if (unit->is_union()) { // execute union without clean up res= unit->exec(); } else { unit->set_limit(first_select); 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->ref_pointer_array, (TABLE_LIST*) 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), (ORDER *) first_select->order_list.first, (ORDER *) first_select->group_list.first, first_select->having, (ORDER*) NULL, (first_select->options | thd->options | SELECT_NO_UNLOCK), derived_result, unit, first_select); } if (!res) { /* Here we entirely fix both TABLE_LIST and list of SELECT's as there were no derived tables */ if (derived_result->flush()) res= TRUE; if (!lex->describe) unit->cleanup(); } else unit->cleanup(); lex->current_select= save_current_select; } return res; }