1 /* 2 ** Copyright (c) 1999, 2000 D. Richard Hipp 3 ** 4 ** This program is free software; you can redistribute it and/or 5 ** modify it under the terms of the GNU General Public 6 ** License as published by the Free Software Foundation; either 7 ** version 2 of the License, or (at your option) any later version. 8 ** 9 ** This program is distributed in the hope that it will be useful, 10 ** but WITHOUT ANY WARRANTY; without even the implied warranty of 11 ** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 12 ** General Public License for more details. 13 ** 14 ** You should have received a copy of the GNU General Public 15 ** License along with this library; if not, write to the 16 ** Free Software Foundation, Inc., 59 Temple Place - Suite 330, 17 ** Boston, MA 02111-1307, USA. 18 ** 19 ** Author contact information: 20 ** [email protected] 21 ** http://www.hwaci.com/drh/ 22 ** 23 ************************************************************************* 24 ** This file contains C code routines that are called by the parser 25 ** to handle DELETE FROM statements. 26 ** 27 ** $Id: delete.c,v 1.6 2000/06/21 13:59:11 drh Exp $ 28 */ 29 #include "sqliteInt.h" 30 31 /* 32 ** Process a DELETE FROM statement. 33 */ 34 void sqliteDeleteFrom( 35 Parse *pParse, /* The parser context */ 36 Token *pTableName, /* The table from which we should delete things */ 37 Expr *pWhere /* The WHERE clause. May be null */ 38 ){ 39 Vdbe *v; /* The virtual database engine */ 40 Table *pTab; /* The table from which records will be deleted */ 41 IdList *pTabList; /* An ID list holding pTab and nothing else */ 42 int end, addr; /* A couple addresses of generated code */ 43 int i; /* Loop counter */ 44 WhereInfo *pWInfo; /* Information about the WHERE clause */ 45 Index *pIdx; /* For looping over indices of the table */ 46 int base; /* Index of the first available table cursor */ 47 48 /* Locate the table which we want to delete. This table has to be 49 ** put in an IdList structure because some of the subroutines we 50 ** will be calling are designed to work with multiple tables and expect 51 ** an IdList* parameter instead of just a Table* parameger. 52 */ 53 pTabList = sqliteIdListAppend(0, pTableName); 54 for(i=0; i<pTabList->nId; i++){ 55 pTabList->a[i].pTab = sqliteFindTable(pParse->db, pTabList->a[i].zName); 56 if( pTabList->a[i].pTab==0 ){ 57 sqliteSetString(&pParse->zErrMsg, "no such table: ", 58 pTabList->a[i].zName, 0); 59 pParse->nErr++; 60 goto delete_from_cleanup; 61 } 62 if( pTabList->a[i].pTab->readOnly ){ 63 sqliteSetString(&pParse->zErrMsg, "table ", pTabList->a[i].zName, 64 " may not be modified", 0); 65 pParse->nErr++; 66 goto delete_from_cleanup; 67 } 68 } 69 pTab = pTabList->a[0].pTab; 70 71 /* Resolve the column names in all the expressions. 72 */ 73 if( pWhere ){ 74 sqliteExprResolveInSelect(pParse, pWhere); 75 if( sqliteExprResolveIds(pParse, pTabList, pWhere) ){ 76 goto delete_from_cleanup; 77 } 78 if( sqliteExprCheck(pParse, pWhere, 0, 0) ){ 79 goto delete_from_cleanup; 80 } 81 } 82 83 /* Begin generating code. 84 */ 85 v = sqliteGetVdbe(pParse); 86 if( v==0 ) goto delete_from_cleanup; 87 88 /* Begin the database scan 89 */ 90 sqliteVdbeAddOp(v, OP_ListOpen, 0, 0, 0, 0); 91 pWInfo = sqliteWhereBegin(pParse, pTabList, pWhere, 1); 92 if( pWInfo==0 ) goto delete_from_cleanup; 93 94 /* Remember the key of every item to be deleted. 95 */ 96 sqliteVdbeAddOp(v, OP_ListWrite, 0, 0, 0, 0); 97 98 /* End the database scan loop. 99 */ 100 sqliteWhereEnd(pWInfo); 101 102 /* Delete every item whose key was written to the list during the 103 ** database scan. We have to delete items after the scan is complete 104 ** because deleting an item can change the scan order. 105 */ 106 base = pParse->nTab; 107 sqliteVdbeAddOp(v, OP_ListRewind, 0, 0, 0, 0); 108 sqliteVdbeAddOp(v, OP_Open, base, 1, pTab->zName, 0); 109 for(i=1, pIdx=pTab->pIndex; pIdx; i++, pIdx=pIdx->pNext){ 110 sqliteVdbeAddOp(v, OP_Open, base+i, 1, pIdx->zName, 0); 111 } 112 end = sqliteVdbeMakeLabel(v); 113 addr = sqliteVdbeAddOp(v, OP_ListRead, 0, end, 0, 0); 114 if( pTab->pIndex ){ 115 sqliteVdbeAddOp(v, OP_Dup, 0, 0, 0, 0); 116 sqliteVdbeAddOp(v, OP_Fetch, base, 0, 0, 0); 117 for(i=1, pIdx=pTab->pIndex; pIdx; i++, pIdx=pIdx->pNext){ 118 int j; 119 sqliteVdbeAddOp(v, OP_Dup, 0, 0, 0, 0); 120 for(j=0; j<pIdx->nColumn; j++){ 121 sqliteVdbeAddOp(v, OP_Field, base, pIdx->aiColumn[j], 0, 0); 122 } 123 sqliteVdbeAddOp(v, OP_MakeKey, pIdx->nColumn, 0, 0, 0); 124 sqliteVdbeAddOp(v, OP_DeleteIdx, base+i, 0, 0, 0); 125 } 126 } 127 sqliteVdbeAddOp(v, OP_Delete, base, 0, 0, 0); 128 sqliteVdbeAddOp(v, OP_Goto, 0, addr, 0, 0); 129 sqliteVdbeAddOp(v, OP_ListClose, 0, 0, 0, end); 130 131 delete_from_cleanup: 132 sqliteIdListDelete(pTabList); 133 sqliteExprDelete(pWhere); 134 return; 135 } 136