drh
190 lines
6.2 KiB
C
190 lines
6.2 KiB
C
/*
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** 2001 September 15
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**
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** The author disclaims copyright to this source code. In place of
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** a legal notice, here is a blessing:
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**
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** May you do good and not evil.
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** May you find forgiveness for yourself and forgive others.
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** May you share freely, never taking more than you give.
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**
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*************************************************************************
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** This file contains C code routines that are called by the parser
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** to handle DELETE FROM statements.
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**
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** $Id: delete.c,v 1.21 2001/11/07 16:48:27 drh Exp $
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*/
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#include "sqliteInt.h"
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/*
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** Process a DELETE FROM statement.
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*/
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void sqliteDeleteFrom(
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Parse *pParse, /* The parser context */
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Token *pTableName, /* The table from which we should delete things */
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Expr *pWhere /* The WHERE clause. May be null */
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){
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Vdbe *v; /* The virtual database engine */
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Table *pTab; /* The table from which records will be deleted */
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IdList *pTabList; /* An ID list holding pTab and nothing else */
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int end, addr; /* A couple addresses of generated code */
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int i; /* Loop counter */
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WhereInfo *pWInfo; /* Information about the WHERE clause */
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Index *pIdx; /* For looping over indices of the table */
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int base; /* Index of the first available table cursor */
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sqlite *db; /* Main database structure */
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int openOp; /* Opcode used to open a cursor to the table */
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if( pParse->nErr || sqlite_malloc_failed ){
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pTabList = 0;
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goto delete_from_cleanup;
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}
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db = pParse->db;
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/* Locate the table which we want to delete. This table has to be
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** put in an IdList structure because some of the subroutines we
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** will be calling are designed to work with multiple tables and expect
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** an IdList* parameter instead of just a Table* parameger.
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*/
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pTabList = sqliteIdListAppend(0, pTableName);
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if( pTabList==0 ) goto delete_from_cleanup;
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for(i=0; i<pTabList->nId; i++){
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pTabList->a[i].pTab = sqliteFindTable(db, pTabList->a[i].zName);
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if( pTabList->a[i].pTab==0 ){
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sqliteSetString(&pParse->zErrMsg, "no such table: ",
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pTabList->a[i].zName, 0);
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pParse->nErr++;
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goto delete_from_cleanup;
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}
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if( pTabList->a[i].pTab->readOnly ){
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sqliteSetString(&pParse->zErrMsg, "table ", pTabList->a[i].zName,
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" may not be modified", 0);
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pParse->nErr++;
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goto delete_from_cleanup;
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}
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}
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pTab = pTabList->a[0].pTab;
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/* Resolve the column names in all the expressions.
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*/
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if( pWhere ){
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sqliteExprResolveInSelect(pParse, pWhere);
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if( sqliteExprResolveIds(pParse, pTabList, pWhere) ){
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goto delete_from_cleanup;
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}
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if( sqliteExprCheck(pParse, pWhere, 0, 0) ){
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goto delete_from_cleanup;
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}
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}
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/* Begin generating code.
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*/
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v = sqliteGetVdbe(pParse);
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if( v==0 ) goto delete_from_cleanup;
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if( (db->flags & SQLITE_InTrans)==0 ){
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sqliteVdbeAddOp(v, OP_Transaction, 0, 0);
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sqliteVdbeAddOp(v, OP_VerifyCookie, db->schema_cookie, 0);
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pParse->schemaVerified = 1;
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}
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/* Initialize the counter of the number of rows deleted, if
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** we are counting rows.
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*/
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if( db->flags & SQLITE_CountRows ){
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sqliteVdbeAddOp(v, OP_Integer, 0, 0);
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}
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/* Special case: A DELETE without a WHERE clause deletes everything.
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** It is easier just to erase the whole table.
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*/
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if( pWhere==0 ){
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if( db->flags & SQLITE_CountRows ){
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/* If counting rows deleted, just count the total number of
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** entries in the table. */
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int endOfLoop = sqliteVdbeMakeLabel(v);
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int addr;
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openOp = pTab->isTemp ? OP_OpenAux : OP_Open;
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sqliteVdbeAddOp(v, openOp, 0, pTab->tnum);
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sqliteVdbeAddOp(v, OP_Rewind, 0, sqliteVdbeCurrentAddr(v)+2);
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addr = sqliteVdbeAddOp(v, OP_AddImm, 1, 0);
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sqliteVdbeAddOp(v, OP_Next, 0, addr);
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sqliteVdbeResolveLabel(v, endOfLoop);
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sqliteVdbeAddOp(v, OP_Close, 0, 0);
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}
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sqliteVdbeAddOp(v, OP_Clear, pTab->tnum, pTab->isTemp);
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for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
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sqliteVdbeAddOp(v, OP_Clear, pIdx->tnum, pTab->isTemp);
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}
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}
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/* The usual case: There is a WHERE clause so we have to scan through
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** the table an pick which records to delete.
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*/
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else{
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/* Begin the database scan
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*/
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pWInfo = sqliteWhereBegin(pParse, pTabList, pWhere, 1);
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if( pWInfo==0 ) goto delete_from_cleanup;
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/* Remember the key of every item to be deleted.
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*/
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sqliteVdbeAddOp(v, OP_ListWrite, 0, 0);
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if( db->flags & SQLITE_CountRows ){
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sqliteVdbeAddOp(v, OP_AddImm, 1, 0);
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}
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/* End the database scan loop.
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*/
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sqliteWhereEnd(pWInfo);
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/* Delete every item whose key was written to the list during the
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** database scan. We have to delete items after the scan is complete
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** because deleting an item can change the scan order.
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*/
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base = pParse->nTab;
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sqliteVdbeAddOp(v, OP_ListRewind, 0, 0);
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openOp = pTab->isTemp ? OP_OpenWrAux : OP_OpenWrite;
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sqliteVdbeAddOp(v, openOp, base, pTab->tnum);
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for(i=1, pIdx=pTab->pIndex; pIdx; i++, pIdx=pIdx->pNext){
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sqliteVdbeAddOp(v, openOp, base+i, pIdx->tnum);
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}
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end = sqliteVdbeMakeLabel(v);
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addr = sqliteVdbeAddOp(v, OP_ListRead, 0, end);
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sqliteVdbeAddOp(v, OP_MoveTo, base, 0);
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if( pTab->pIndex ){
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for(i=1, pIdx=pTab->pIndex; pIdx; i++, pIdx=pIdx->pNext){
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int j;
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sqliteVdbeAddOp(v, OP_Recno, base, 0);
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for(j=0; j<pIdx->nColumn; j++){
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sqliteVdbeAddOp(v, OP_Column, base, pIdx->aiColumn[j]);
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}
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sqliteVdbeAddOp(v, OP_MakeIdxKey, pIdx->nColumn, 0);
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sqliteVdbeAddOp(v, OP_IdxDelete, base+i, 0);
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}
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}
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sqliteVdbeAddOp(v, OP_Delete, base, 0);
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sqliteVdbeAddOp(v, OP_Goto, 0, addr);
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sqliteVdbeResolveLabel(v, end);
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sqliteVdbeAddOp(v, OP_ListReset, 0, 0);
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}
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if( (db->flags & SQLITE_InTrans)==0 ){
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sqliteVdbeAddOp(v, OP_Commit, 0, 0);
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}
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/*
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** Return the number of rows that were deleted.
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*/
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if( db->flags & SQLITE_CountRows ){
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sqliteVdbeAddOp(v, OP_ColumnCount, 1, 0);
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sqliteVdbeAddOp(v, OP_ColumnName, 0, 0);
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sqliteVdbeChangeP3(v, -1, "rows deleted", P3_STATIC);
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sqliteVdbeAddOp(v, OP_Callback, 1, 0);
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}
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delete_from_cleanup:
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sqliteIdListDelete(pTabList);
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sqliteExprDelete(pWhere);
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return;
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}
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