/* 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" static int mysql_derived(THD *thd, LEX *lex, SELECT_LEX_UNIT *s, TABLE_LIST *t); /* Resolve derived tables in all queries SYNOPSIS mysql_handle_derived() lex LEX for this thread RETURN 0 ok -1 Error 1 Error and error message given */ int mysql_handle_derived(LEX *lex) { if (lex->derived_tables) { 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) { int res; if (cursor->derived && (res=mysql_derived(lex->thd, lex, cursor->derived, cursor))) { return res; } } 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; } } } return 0; } /* 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() RETURN 0 ok 1 Error -1 Error and error message given */ static int mysql_derived(THD *thd, LEX *lex, SELECT_LEX_UNIT *unit, TABLE_LIST *org_table_list) { SELECT_LEX *first_select= unit->first_select(); TABLE *table; int res; select_union *derived_result; bool is_union= first_select->next_select() && first_select->next_select()->linkage == UNION_TYPE; bool is_subsel= first_select->first_inner_unit() ? 1: 0; SELECT_LEX *save_current_select= lex->current_select; DBUG_ENTER("mysql_derived"); if (!(derived_result= new select_union(0))) DBUG_RETURN(1); // out of memory // st_select_lex_unit::prepare correctly work for single select if ((res= unit->prepare(thd, derived_result, 0))) goto exit; derived_result->tmp_table_param.init(); derived_result->tmp_table_param.field_count= unit->types.elements; /* Temp table is created so that it hounours if UNION without ALL is to be processed */ if (!(table= create_tmp_table(thd, &derived_result->tmp_table_param, unit->types, (ORDER*) 0, is_union && unit->union_distinct, 1, (first_select->options | thd->options | TMP_TABLE_ALL_COLUMNS), HA_POS_ERROR, org_table_list->alias))) { res= -1; goto exit; } derived_result->set_table(table); /* if it is preparation PS only then we do not need real data and we can skip execution (and parameters is not defined, too) */ if (!thd->only_prepare()) { if (is_union) { // execute union without clean up if (!(res= unit->prepare(thd, derived_result, SELECT_NO_UNLOCK))) res= unit->exec(); } else { unit->offset_limit_cnt= first_select->offset_limit; unit->select_limit_cnt= first_select->select_limit+ first_select->offset_limit; if (unit->select_limit_cnt < first_select->select_limit) unit->select_limit_cnt= HA_POS_ERROR; 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= 1; else { org_table_list->real_name= table->real_name; org_table_list->table= table; if (org_table_list->table_list) { org_table_list->table_list->real_name= table->real_name; org_table_list->table_list->table= table; } table->derived_select_number= first_select->select_number; table->tmp_table= TMP_TABLE; #ifndef NO_EMBEDDED_ACCESS_CHECKS table->grant.privilege= SELECT_ACL; #endif org_table_list->db= (char *)""; // Force read of table stats in the optimizer table->file->info(HA_STATUS_VARIABLE); } if (!lex->describe) unit->cleanup(); 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: delete derived_result; lex->current_select= save_current_select; } DBUG_RETURN(res); }