/*
** Copyright (c) 1999, 2000 D. Richard Hipp
**
** 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 library; if not, write to the
** Free Software Foundation, Inc., 59 Temple Place - Suite 330,
** Boston, MA 02111-1307, USA.
**
** Author contact information:
** drh@hwaci.com
** http://www.hwaci.com/drh/
**
*************************************************************************
** This file contains C code routines that are called by the parser
** to handle UPDATE statements.
**
** $Id: update.c,v 1.2 2000/06/02 01:17:38 drh Exp $
*/
#include "sqliteInt.h"
/*
** Process an UPDATE statement.
*/
void sqliteUpdate(
Parse *pParse, /* The parser context */
Token *pTableName, /* The table in which we should change things */
ExprList *pChanges, /* Things to be changed */
Expr *pWhere /* The WHERE clause. May be null */
){
int i, j; /* Loop counters */
Table *pTab; /* The table to be updated */
IdList *pTabList = 0; /* List containing only pTab */
int end, addr; /* A couple of addresses in the generated code */
WhereInfo *pWInfo; /* Information about the WHERE clause */
Vdbe *v; /* The virtual database engine */
Index *pIdx; /* For looping over indices */
int nIdx; /* Number of indices that need updating */
Index **apIdx = 0; /* An array of indices that need updating too */
int *aXRef = 0; /* aXRef[i] is the index in pChanges->a[] of the
** an expression for the i-th field of the table.
** aXRef[i]==-1 if the i-th field is not changed. */
/* Locate the table which we want to update. This table has to be
** put in an IdList structure because some of the subroutines will
** 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);
for(i=0; i<pTabList->nId; i++){
pTabList->a[i].pTab = sqliteFindTable(pParse->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 update_cleanup;
}
if( pTabList->a[i].pTab->readOnly ){
sqliteSetString(&pParse->zErrMsg, "table ", pTabList->a[i].zName,
" may not be modified", 0);
pParse->nErr++;
goto update_cleanup;
}
}
pTab = pTabList->a[0].pTab;
aXRef = sqliteMalloc( sizeof(int) * pTab->nCol );
if( aXRef==0 ) goto update_cleanup;
for(i=0; i<pTab->nCol; i++) aXRef[i] = -1;
/* Resolve the field names in all the expressions in both the
** WHERE clause and in the new values. Also find the field index
** for each field to be updated in the pChanges array.
*/
if( pWhere ){
if( sqliteExprResolveIds(pParse, pTabList, pWhere) ){
goto update_cleanup;
}
if( sqliteExprCheck(pParse, pWhere, 0, 0) ){
goto update_cleanup;
}
}
for(i=0; i<pChanges->nExpr; i++){
if( sqliteExprResolveIds(pParse, pTabList, pChanges->a[i].pExpr) ){
goto update_cleanup;
}
if( sqliteExprCheck(pParse, pChanges->a[i].pExpr, 0, 0) ){
goto update_cleanup;
}
for(j=0; j<pTab->nCol; j++){
if( strcmp(pTab->azCol[j], pChanges->a[i].zName)==0 ){
pChanges->a[i].idx = j;
aXRef[j] = i;
break;
}
}
if( j>=pTab->nCol ){
sqliteSetString(&pParse->zErrMsg, "no such field: ",
pChanges->a[i].zName, 0);
pParse->nErr++;
goto update_cleanup;
}
}
/* Allocate memory for the array apIdx[] and fill it pointers to every
** index that needs to be updated. Indices only need updating if their
** key includes one of the fields named in pChanges.
*/
for(nIdx=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
for(i=0; i<pIdx->nField; i++){
if( aXRef[pIdx->aiField[i]]>=0 ) break;
}
if( i<pIdx->nField ) nIdx++;
}
apIdx = sqliteMalloc( sizeof(Index*) * nIdx );
if( apIdx==0 ) goto update_cleanup;
for(nIdx=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
for(i=0; i<pIdx->nField; i++){
if( aXRef[pIdx->aiField[i]]>=0 ) break;
}
if( i<pIdx->nField ) apIdx[nIdx++] = pIdx;
}
/* Begin generating code.
*/
v = pParse->pVdbe;
if( v==0 ){
v = pParse->pVdbe = sqliteVdbeCreate(pParse->db->pBe);
}
if( v==0 ) goto update_cleanup;
/* Begin the database scan
*/
sqliteVdbeAddOp(v, OP_ListOpen, 0, 0, 0, 0);
pWInfo = sqliteWhereBegin(pParse, pTabList, pWhere, 1);
if( pWInfo==0 ) goto update_cleanup;
/* Remember the index of every item to be updated.
*/
sqliteVdbeAddOp(v, OP_ListWrite, 0, 0, 0, 0);
/* End the database scan loop.
*/
sqliteWhereEnd(pWInfo);
/* Rewind the list of records that need to be updated and
** open every index that needs updating.
*/
sqliteVdbeAddOp(v, OP_ListRewind, 0, 0, 0, 0);
sqliteVdbeAddOp(v, OP_Open, 0, 1, pTab->zName, 0);
for(i=0; i<nIdx; i++){
sqliteVdbeAddOp(v, OP_Open, i+1, 1, apIdx[i]->zName, 0);
}
/* Loop over every record that needs updating. We have to load
** the old data for each record to be updated because some fields
** might not change and we will need to copy the old value, therefore.
** Also, the old data is needed to delete the old index entires.
*/
end = sqliteVdbeMakeLabel(v);
addr = sqliteVdbeAddOp(v, OP_ListRead, 0, end, 0, 0);
sqliteVdbeAddOp(v, OP_Dup, 0, 0, 0, 0);
sqliteVdbeAddOp(v, OP_Fetch, 0, 0, 0, 0);
/* Delete the old indices for the current record.
*/
for(i=0; i<nIdx; i++){
sqliteVdbeAddOp(v, OP_Dup, 0, 0, 0, 0);
pIdx = apIdx[i];
for(j=0; j<pIdx->nField; j++){
sqliteVdbeAddOp(v, OP_Field, 0, pIdx->aiField[j], 0, 0);
}
sqliteVdbeAddOp(v, OP_MakeKey, pIdx->nField, 0, 0, 0);
sqliteVdbeAddOp(v, OP_DeleteIdx, i+1, 0, 0, 0);
}
/* Compute a completely new data for this record.
*/
for(i=0; i<pTab->nCol; i++){
j = aXRef[i];
if( j<0 ){
sqliteVdbeAddOp(v, OP_Field, 0, i, 0, 0);
}else{
sqliteExprCode(pParse, pChanges->a[j].pExpr);
}
}
/* Insert new index entries that correspond to the new data
*/
for(i=0; i<nIdx; i++){
sqliteVdbeAddOp(v, OP_Dup, pTab->nCol, 0, 0, 0); /* The KEY */
pIdx = apIdx[i];
for(j=0; j<pIdx->nField; j++){
sqliteVdbeAddOp(v, OP_Dup, j+pTab->nCol-pIdx->aiField[j], 0, 0, 0);
}
sqliteVdbeAddOp(v, OP_MakeKey, pIdx->nField, 0, 0, 0);
sqliteVdbeAddOp(v, OP_PutIdx, i+1, 0, 0, 0);
}
/* Write the new data back into the database.
*/
sqliteVdbeAddOp(v, OP_MakeRecord, pTab->nCol, 0, 0, 0);
sqliteVdbeAddOp(v, OP_Put, 0, 0, 0, 0);
/* Repeat the above with the next record to be updated, until
** all record selected by the WHERE clause have been updated.
*/
sqliteVdbeAddOp(v, OP_Goto, 0, addr, 0, 0);
sqliteVdbeAddOp(v, OP_ListClose, 0, 0, 0, end);
update_cleanup:
sqliteFree(apIdx);
sqliteFree(aXRef);
sqliteIdListDelete(pTabList);
sqliteExprListDelete(pChanges);
sqliteExprDelete(pWhere);
return;
}