/* 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; either version 2 of the License, or (at your option) any later version. 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" #include "sql_acl.h" /* Resolve derived tables in all queries SYNOPSIS mysql_derived(THD *thd, LEX *lex, SELECT_LEX_UNIT *unit, TABLE_LIST *t) thd Thread handle lex LEX for this thread unit node that contains all SELECT's for derived tables t 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 created, 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. After table creation, the above TABLE_LIST is updated with a new table. This function is called before any command containing derived table is executed. Derived tables is stored in thd->derived_tables and freed in close_thread_tables() TODO Move creation of derived tables in open_and_lock_tables() RETURN 0 ok 1 Error -1 Error and error message given */ int mysql_derived(THD *thd, LEX *lex, SELECT_LEX_UNIT *unit, TABLE_LIST *org_table_list) { SELECT_LEX *select_cursor= unit->first_select(); List<Item> item_list; TABLE *table; int res; select_union *derived_result; TABLE_LIST *tables= (TABLE_LIST *)select_cursor->table_list.first; TMP_TABLE_PARAM tmp_table_param; bool is_union= select_cursor->next_select() && select_cursor->next_select()->linkage == UNION_TYPE; bool is_subsel= select_cursor->first_inner_unit() ? 1: 0; SELECT_LEX *save_current_select= lex->current_select; DBUG_ENTER("mysql_derived"); /* In create_total_list, derived tables have to be treated in case of EXPLAIN, This is because unit/node is not deleted in that case. Current code in this function has to be improved to recognize better when this function is called from derived tables and when from other functions. */ if ((is_union || is_subsel) && unit->create_total_list(thd, lex, &tables, 1)) DBUG_RETURN(-1); /* We have to do access checks here as this code is executed before any sql command is started to execute. */ #ifndef NO_EMBEDDED_ACCESS_CHECKS if (tables) res= check_table_access(thd,SELECT_ACL, tables,0); else res= check_access(thd, SELECT_ACL, any_db,0,0,0); if (res) DBUG_RETURN(1); #endif if (!(res=open_and_lock_tables(thd,tables))) { if (is_union || is_subsel) { /* The following code is a re-do of fix_tables_pointers() found in sql_select.cc for UNION's within derived tables. The only difference is in navigation, as in derived tables we care for this level only. */ fix_tables_pointers(unit); } lex->current_select= select_cursor; TABLE_LIST *first_table= (TABLE_LIST*) select_cursor->table_list.first; /* Setting up. A must if a join or IGNORE, USE or similar are utilised */ if (setup_tables(first_table) || setup_wild(thd, first_table, select_cursor->item_list, 0, select_cursor->with_wild)) { res= -1; goto exit; } /* This is done in order to redo all field optimisations when any of the involved tables is used in the outer query */ if (tables) { for (TABLE_LIST *cursor= tables; cursor; cursor= cursor->next) cursor->table->clear_query_id= 1; } item_list= select_cursor->item_list; select_cursor->with_wild= 0; if (select_cursor->setup_ref_array(thd, select_cursor->order_list.elements + select_cursor->group_list.elements) || setup_fields(thd, select_cursor->ref_pointer_array, first_table, item_list, 0, 0, 1)) { res= -1; goto exit; } // Item list should be fix_fielded yet another time in JOIN::prepare unfix_item_list(item_list); bzero((char*) &tmp_table_param,sizeof(tmp_table_param)); tmp_table_param.field_count= item_list.elements; /* Temp table is created so that it hounours if UNION without ALL is to be processed */ if (!(table= create_tmp_table(thd, &tmp_table_param, item_list, (ORDER*) 0, is_union && !unit->union_option, 1, (select_cursor->options | thd->options | TMP_TABLE_ALL_COLUMNS), HA_POS_ERROR, org_table_list->alias))) { res= -1; goto exit; } if ((derived_result=new select_union(table))) { derived_result->tmp_table_param=tmp_table_param; unit->offset_limit_cnt= select_cursor->offset_limit; unit->select_limit_cnt= select_cursor->select_limit+ select_cursor->offset_limit; if (unit->select_limit_cnt < select_cursor->select_limit) unit->select_limit_cnt= HA_POS_ERROR; if (unit->select_limit_cnt == HA_POS_ERROR) select_cursor->options&= ~OPTION_FOUND_ROWS; if (is_union) res= mysql_union(thd, lex, derived_result, unit, 1); else res= mysql_select(thd, &select_cursor->ref_pointer_array, (TABLE_LIST*) select_cursor->table_list.first, select_cursor->with_wild, select_cursor->item_list, select_cursor->where, (select_cursor->order_list.elements+ select_cursor->group_list.elements), (ORDER *) select_cursor->order_list.first, (ORDER *) select_cursor->group_list.first, select_cursor->having, (ORDER*) NULL, (select_cursor->options | thd->options | SELECT_NO_UNLOCK), derived_result, unit, select_cursor, 1); 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= 1; else { org_table_list->real_name=table->real_name; org_table_list->table=table; table->derived_select_number= select_cursor->select_number; table->tmp_table= TMP_TABLE; #ifndef NO_EMBEDDED_ACCESS_CHECKS org_table_list->grant.privilege= SELECT_ACL; #endif if (lex->describe) { // to fix a problem in EXPLAIN if (tables) { for (TABLE_LIST *cursor= tables; cursor; cursor= cursor->next) if (cursor->table_list) cursor->table_list->table=cursor->table; } } else unit->exclude_level(); org_table_list->db= (char *)""; // Force read of table stats in the optimizer table->file->info(HA_STATUS_VARIABLE); } } delete derived_result; } if (res) free_tmp_table(thd, table); else { /* Add new temporary table to list of open derived tables */ table->next= thd->derived_tables; thd->derived_tables= table; } exit: lex->current_select= save_current_select; close_thread_tables(thd, 0, 1); } DBUG_RETURN(res); }