/*
** 2001 September 15
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains C code routines that are called by the parser
** to handle DELETE FROM statements.
**
** $Id: delete.c,v 1.20 2001/11/07 14:22:00 drh Exp $
*/
#include "sqliteInt.h"
/*
** Process a DELETE FROM statement.
*/
void sqliteDeleteFrom(
Parse *pParse, /* The parser context */
Token *pTableName, /* The table from which we should delete things */
Expr *pWhere /* The WHERE clause. May be null */
){
Vdbe *v; /* The virtual database engine */
Table *pTab; /* The table from which records will be deleted */
IdList *pTabList; /* An ID list holding pTab and nothing else */
int end, addr; /* A couple addresses of generated code */
int i; /* Loop counter */
WhereInfo *pWInfo; /* Information about the WHERE clause */
Index *pIdx; /* For looping over indices of the table */
int base; /* Index of the first available table cursor */
sqlite *db; /* Main database structure */
int openOp; /* Opcode used to open a cursor to the table */
if( pParse->nErr || sqlite_malloc_failed ){
pTabList = 0;
goto delete_from_cleanup;
}
db = pParse->db;
/* Locate the table which we want to delete. This table has to be
** put in an IdList structure because some of the subroutines we
** will be calling are designed to work with multiple tables and expect
** an IdList* parameter instead of just a Table* parameger.
*/
pTabList = sqliteIdListAppend(0, pTableName);
if( pTabList==0 ) goto delete_from_cleanup;
for(i=0; i<pTabList->nId; i++){
pTabList->a[i].pTab = sqliteFindTable(db, pTabList->a[i].zName);
if( pTabList->a[i].pTab==0 ){
sqliteSetString(&pParse->zErrMsg, "no such table: ",
pTabList->a[i].zName, 0);
pParse->nErr++;
goto delete_from_cleanup;
}
if( pTabList->a[i].pTab->readOnly ){
sqliteSetString(&pParse->zErrMsg, "table ", pTabList->a[i].zName,
" may not be modified", 0);
pParse->nErr++;
goto delete_from_cleanup;
}
}
pTab = pTabList->a[0].pTab;
/* Resolve the column names in all the expressions.
*/
if( pWhere ){
sqliteExprResolveInSelect(pParse, pWhere);
if( sqliteExprResolveIds(pParse, pTabList, pWhere) ){
goto delete_from_cleanup;
}
if( sqliteExprCheck(pParse, pWhere, 0, 0) ){
goto delete_from_cleanup;
}
}
/* Begin generating code.
*/
v = sqliteGetVdbe(pParse);
if( v==0 ) goto delete_from_cleanup;
if( (db->flags & SQLITE_InTrans)==0 ){
sqliteVdbeAddOp(v, OP_Transaction, 0, 0);
sqliteVdbeAddOp(v, OP_VerifyCookie, db->schema_cookie, 0);
pParse->schemaVerified = 1;
}
/* Initialize the counter of the number of rows deleted, if
** we are counting rows.
*/
if( db->flags & SQLITE_CountRows ){
sqliteVdbeAddOp(v, OP_Integer, 0, 0);
}
/* Special case: A DELETE without a WHERE clause deletes everything.
** It is easier just to erase the whole table.
*/
if( pWhere==0 ){
if( db->flags & SQLITE_CountRows ){
/* If counting rows deleted, just count the total number of
** entries in the table. */
int endOfLoop = sqliteVdbeMakeLabel(v);
int addr;
openOp = pTab->isTemp ? OP_OpenAux : OP_Open;
sqliteVdbeAddOp(v, openOp, 0, pTab->tnum);
sqliteVdbeAddOp(v, OP_Rewind, 0, 0);
addr = sqliteVdbeAddOp(v, OP_Next, 0, endOfLoop);
sqliteVdbeAddOp(v, OP_AddImm, 1, 0);
sqliteVdbeAddOp(v, OP_Goto, 0, addr);
sqliteVdbeResolveLabel(v, endOfLoop);
sqliteVdbeAddOp(v, OP_Close, 0, 0);
}
sqliteVdbeAddOp(v, OP_Clear, pTab->tnum, pTab->isTemp);
for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
sqliteVdbeAddOp(v, OP_Clear, pIdx->tnum, pTab->isTemp);
}
}
/* The usual case: There is a WHERE clause so we have to scan through
** the table an pick which records to delete.
*/
else{
/* Begin the database scan
*/
pWInfo = sqliteWhereBegin(pParse, pTabList, pWhere, 1);
if( pWInfo==0 ) goto delete_from_cleanup;
/* Remember the key of every item to be deleted.
*/
sqliteVdbeAddOp(v, OP_ListWrite, 0, 0);
if( db->flags & SQLITE_CountRows ){
sqliteVdbeAddOp(v, OP_AddImm, 1, 0);
}
/* End the database scan loop.
*/
sqliteWhereEnd(pWInfo);
/* Delete every item whose key was written to the list during the
** database scan. We have to delete items after the scan is complete
** because deleting an item can change the scan order.
*/
base = pParse->nTab;
sqliteVdbeAddOp(v, OP_ListRewind, 0, 0);
openOp = pTab->isTemp ? OP_OpenWrAux : OP_OpenWrite;
sqliteVdbeAddOp(v, openOp, base, pTab->tnum);
for(i=1, pIdx=pTab->pIndex; pIdx; i++, pIdx=pIdx->pNext){
sqliteVdbeAddOp(v, openOp, base+i, pIdx->tnum);
}
end = sqliteVdbeMakeLabel(v);
addr = sqliteVdbeAddOp(v, OP_ListRead, 0, end);
sqliteVdbeAddOp(v, OP_MoveTo, base, 0);
if( pTab->pIndex ){
for(i=1, pIdx=pTab->pIndex; pIdx; i++, pIdx=pIdx->pNext){
int j;
sqliteVdbeAddOp(v, OP_Recno, base, 0);
for(j=0; j<pIdx->nColumn; j++){
sqliteVdbeAddOp(v, OP_Column, base, pIdx->aiColumn[j]);
}
sqliteVdbeAddOp(v, OP_MakeIdxKey, pIdx->nColumn, 0);
sqliteVdbeAddOp(v, OP_IdxDelete, base+i, 0);
}
}
sqliteVdbeAddOp(v, OP_Delete, base, 0);
sqliteVdbeAddOp(v, OP_Goto, 0, addr);
sqliteVdbeResolveLabel(v, end);
sqliteVdbeAddOp(v, OP_ListReset, 0, 0);
}
if( (db->flags & SQLITE_InTrans)==0 ){
sqliteVdbeAddOp(v, OP_Commit, 0, 0);
}
/*
** Return the number of rows that were deleted.
*/
if( db->flags & SQLITE_CountRows ){
sqliteVdbeAddOp(v, OP_ColumnCount, 1, 0);
sqliteVdbeAddOp(v, OP_ColumnName, 0, 0);
sqliteVdbeChangeP3(v, -1, "rows deleted", P3_STATIC);
sqliteVdbeAddOp(v, OP_Callback, 1, 0);
}
delete_from_cleanup:
sqliteIdListDelete(pTabList);
sqliteExprDelete(pWhere);
return;
}