OpenSolaris_b135/lib/libsqlite/src/delete.c
#pragma ident "%Z%%M% %I% %E% SMI"
/*
** 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 1.61 2004/02/24 01:05:32 drh Exp $
*/
#include "sqliteInt.h"
/*
** Look up every table that is named in pSrc. If any table is not found,
** add an error message to pParse->zErrMsg and return NULL. If all tables
** are found, return a pointer to the last table.
*/
Table *sqliteSrcListLookup(Parse *pParse, SrcList *pSrc){
Table *pTab = 0;
int i;
for(i=0; i<pSrc->nSrc; i++){
const char *zTab = pSrc->a[i].zName;
const char *zDb = pSrc->a[i].zDatabase;
pTab = sqliteLocateTable(pParse, zTab, zDb);
pSrc->a[i].pTab = pTab;
}
return pTab;
}
/*
** Check to make sure the given table is writable. If it is not
** writable, generate an error message and return 1. If it is
** writable return 0;
*/
int sqliteIsReadOnly(Parse *pParse, Table *pTab, int viewOk){
if( pTab->readOnly ){
sqliteErrorMsg(pParse, "table %s may not be modified", pTab->zName);
return 1;
}
if( !viewOk && pTab->pSelect ){
sqliteErrorMsg(pParse, "cannot modify %s because it is a view",pTab->zName);
return 1;
}
return 0;
}
/*
** Process a DELETE FROM statement.
*/
void sqliteDeleteFrom(
Parse *pParse, /* The parser context */
SrcList *pTabList, /* 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 */
const char *zDb; /* Name of database holding pTab */
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 iCur; /* VDBE Cursor number for pTab */
sqlite *db; /* Main database structure */
int isView; /* True if attempting to delete from a view */
AuthContext sContext; /* Authorization context */
int row_triggers_exist = 0; /* True if any triggers exist */
int before_triggers; /* True if there are BEFORE triggers */
int after_triggers; /* True if there are AFTER triggers */
int oldIdx = -1; /* Cursor for the OLD table of AFTER triggers */
sContext.pParse = 0;
if( pParse->nErr || sqlite_malloc_failed ){
pTabList = 0;
goto delete_from_cleanup;
}
db = pParse->db;
assert( pTabList->nSrc==1 );
/* Locate the table which we want to delete. This table has to be
** put in an SrcList structure because some of the subroutines we
** will be calling are designed to work with multiple tables and expect
** an SrcList* parameter instead of just a Table* parameter.
*/
pTab = sqliteSrcListLookup(pParse, pTabList);
if( pTab==0 ) goto delete_from_cleanup;
before_triggers = sqliteTriggersExist(pParse, pTab->pTrigger,
TK_DELETE, TK_BEFORE, TK_ROW, 0);
after_triggers = sqliteTriggersExist(pParse, pTab->pTrigger,
TK_DELETE, TK_AFTER, TK_ROW, 0);
row_triggers_exist = before_triggers || after_triggers;
isView = pTab->pSelect!=0;
if( sqliteIsReadOnly(pParse, pTab, before_triggers) ){
goto delete_from_cleanup;
}
assert( pTab->iDb<db->nDb );
zDb = db->aDb[pTab->iDb].zName;
if( sqliteAuthCheck(pParse, SQLITE_DELETE, pTab->zName, 0, zDb) ){
goto delete_from_cleanup;
}
/* If pTab is really a view, make sure it has been initialized.
*/
if( isView && sqliteViewGetColumnNames(pParse, pTab) ){
goto delete_from_cleanup;
}
/* Allocate a cursor used to store the old.* data for a trigger.
*/
if( row_triggers_exist ){
oldIdx = pParse->nTab++;
}
/* Resolve the column names in all the expressions.
*/
assert( pTabList->nSrc==1 );
iCur = pTabList->a[0].iCursor = pParse->nTab++;
if( pWhere ){
if( sqliteExprResolveIds(pParse, pTabList, 0, pWhere) ){
goto delete_from_cleanup;
}
if( sqliteExprCheck(pParse, pWhere, 0, 0) ){
goto delete_from_cleanup;
}
}
/* Start the view context
*/
if( isView ){
sqliteAuthContextPush(pParse, &sContext, pTab->zName);
}
/* Begin generating code.
*/
v = sqliteGetVdbe(pParse);
if( v==0 ){
goto delete_from_cleanup;
}
sqliteBeginWriteOperation(pParse, row_triggers_exist, pTab->iDb);
/* If we are trying to delete from a view, construct that view into
** a temporary table.
*/
if( isView ){
Select *pView = sqliteSelectDup(pTab->pSelect);
sqliteSelect(pParse, pView, SRT_TempTable, iCur, 0, 0, 0);
sqliteSelectDelete(pView);
}
/* 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. Note, however, that
** this means that the row change count will be incorrect.
*/
if( pWhere==0 && !row_triggers_exist ){
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;
if( !isView ){
sqliteVdbeAddOp(v, OP_Integer, pTab->iDb, 0);
sqliteVdbeAddOp(v, OP_OpenRead, iCur, pTab->tnum);
}
sqliteVdbeAddOp(v, OP_Rewind, iCur, sqliteVdbeCurrentAddr(v)+2);
addr = sqliteVdbeAddOp(v, OP_AddImm, 1, 0);
sqliteVdbeAddOp(v, OP_Next, iCur, addr);
sqliteVdbeResolveLabel(v, endOfLoop);
sqliteVdbeAddOp(v, OP_Close, iCur, 0);
}
if( !isView ){
sqliteVdbeAddOp(v, OP_Clear, pTab->tnum, pTab->iDb);
for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
sqliteVdbeAddOp(v, OP_Clear, pIdx->tnum, pIdx->iDb);
}
}
}
/* The usual case: There is a WHERE clause so we have to scan through
** the table and pick which records to delete.
*/
else{
/* Begin the database scan
*/
pWInfo = sqliteWhereBegin(pParse, pTabList, pWhere, 1, 0);
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);
/* Open the pseudo-table used to store OLD if there are triggers.
*/
if( row_triggers_exist ){
sqliteVdbeAddOp(v, OP_OpenPseudo, oldIdx, 0);
}
/* 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.
*/
sqliteVdbeAddOp(v, OP_ListRewind, 0, 0);
end = sqliteVdbeMakeLabel(v);
/* This is the beginning of the delete loop when there are
** row triggers.
*/
if( row_triggers_exist ){
addr = sqliteVdbeAddOp(v, OP_ListRead, 0, end);
sqliteVdbeAddOp(v, OP_Dup, 0, 0);
if( !isView ){
sqliteVdbeAddOp(v, OP_Integer, pTab->iDb, 0);
sqliteVdbeAddOp(v, OP_OpenRead, iCur, pTab->tnum);
}
sqliteVdbeAddOp(v, OP_MoveTo, iCur, 0);
sqliteVdbeAddOp(v, OP_Recno, iCur, 0);
sqliteVdbeAddOp(v, OP_RowData, iCur, 0);
sqliteVdbeAddOp(v, OP_PutIntKey, oldIdx, 0);
if( !isView ){
sqliteVdbeAddOp(v, OP_Close, iCur, 0);
}
sqliteCodeRowTrigger(pParse, TK_DELETE, 0, TK_BEFORE, pTab, -1,
oldIdx, (pParse->trigStack)?pParse->trigStack->orconf:OE_Default,
addr);
}
if( !isView ){
/* Open cursors for the table we are deleting from and all its
** indices. If there are row triggers, this happens inside the
** OP_ListRead loop because the cursor have to all be closed
** before the trigger fires. If there are no row triggers, the
** cursors are opened only once on the outside the loop.
*/
pParse->nTab = iCur + 1;
sqliteOpenTableAndIndices(pParse, pTab, iCur);
/* This is the beginning of the delete loop when there are no
** row triggers */
if( !row_triggers_exist ){
addr = sqliteVdbeAddOp(v, OP_ListRead, 0, end);
}
/* Delete the row */
sqliteGenerateRowDelete(db, v, pTab, iCur, pParse->trigStack==0);
}
/* If there are row triggers, close all cursors then invoke
** the AFTER triggers
*/
if( row_triggers_exist ){
if( !isView ){
for(i=1, pIdx=pTab->pIndex; pIdx; i++, pIdx=pIdx->pNext){
sqliteVdbeAddOp(v, OP_Close, iCur + i, pIdx->tnum);
}
sqliteVdbeAddOp(v, OP_Close, iCur, 0);
}
sqliteCodeRowTrigger(pParse, TK_DELETE, 0, TK_AFTER, pTab, -1,
oldIdx, (pParse->trigStack)?pParse->trigStack->orconf:OE_Default,
addr);
}
/* End of the delete loop */
sqliteVdbeAddOp(v, OP_Goto, 0, addr);
sqliteVdbeResolveLabel(v, end);
sqliteVdbeAddOp(v, OP_ListReset, 0, 0);
/* Close the cursors after the loop if there are no row triggers */
if( !row_triggers_exist ){
for(i=1, pIdx=pTab->pIndex; pIdx; i++, pIdx=pIdx->pNext){
sqliteVdbeAddOp(v, OP_Close, iCur + i, pIdx->tnum);
}
sqliteVdbeAddOp(v, OP_Close, iCur, 0);
pParse->nTab = iCur;
}
}
sqliteVdbeAddOp(v, OP_SetCounts, 0, 0);
sqliteEndWriteOperation(pParse);
/*
** Return the number of rows that were deleted.
*/
if( db->flags & SQLITE_CountRows ){
sqliteVdbeAddOp(v, OP_ColumnName, 0, 1);
sqliteVdbeChangeP3(v, -1, "rows deleted", P3_STATIC);
sqliteVdbeAddOp(v, OP_Callback, 1, 0);
}
delete_from_cleanup:
sqliteAuthContextPop(&sContext);
sqliteSrcListDelete(pTabList);
sqliteExprDelete(pWhere);
return;
}
/*
** This routine generates VDBE code that causes a single row of a
** single table to be deleted.
**
** The VDBE must be in a particular state when this routine is called.
** These are the requirements:
**
** 1. A read/write cursor pointing to pTab, the table containing the row
** to be deleted, must be opened as cursor number "base".
**
** 2. Read/write cursors for all indices of pTab must be open as
** cursor number base+i for the i-th index.
**
** 3. The record number of the row to be deleted must be on the top
** of the stack.
**
** This routine pops the top of the stack to remove the record number
** and then generates code to remove both the table record and all index
** entries that point to that record.
*/
void sqliteGenerateRowDelete(
sqlite *db, /* The database containing the index */
Vdbe *v, /* Generate code into this VDBE */
Table *pTab, /* Table containing the row to be deleted */
int iCur, /* Cursor number for the table */
int count /* Increment the row change counter */
){
int addr;
addr = sqliteVdbeAddOp(v, OP_NotExists, iCur, 0);
sqliteGenerateRowIndexDelete(db, v, pTab, iCur, 0);
sqliteVdbeAddOp(v, OP_Delete, iCur,
(count?OPFLAG_NCHANGE:0) | OPFLAG_CSCHANGE);
sqliteVdbeChangeP2(v, addr, sqliteVdbeCurrentAddr(v));
}
/*
** This routine generates VDBE code that causes the deletion of all
** index entries associated with a single row of a single table.
**
** The VDBE must be in a particular state when this routine is called.
** These are the requirements:
**
** 1. A read/write cursor pointing to pTab, the table containing the row
** to be deleted, must be opened as cursor number "iCur".
**
** 2. Read/write cursors for all indices of pTab must be open as
** cursor number iCur+i for the i-th index.
**
** 3. The "iCur" cursor must be pointing to the row that is to be
** deleted.
*/
void sqliteGenerateRowIndexDelete(
sqlite *db, /* The database containing the index */
Vdbe *v, /* Generate code into this VDBE */
Table *pTab, /* Table containing the row to be deleted */
int iCur, /* Cursor number for the table */
char *aIdxUsed /* Only delete if aIdxUsed!=0 && aIdxUsed[i]!=0 */
){
int i;
Index *pIdx;
for(i=1, pIdx=pTab->pIndex; pIdx; i++, pIdx=pIdx->pNext){
int j;
if( aIdxUsed!=0 && aIdxUsed[i-1]==0 ) continue;
sqliteVdbeAddOp(v, OP_Recno, iCur, 0);
for(j=0; j<pIdx->nColumn; j++){
int idx = pIdx->aiColumn[j];
if( idx==pTab->iPKey ){
sqliteVdbeAddOp(v, OP_Dup, j, 0);
}else{
sqliteVdbeAddOp(v, OP_Column, iCur, idx);
}
}
sqliteVdbeAddOp(v, OP_MakeIdxKey, pIdx->nColumn, 0);
if( db->file_format>=4 ) sqliteAddIdxKeyType(v, pIdx);
sqliteVdbeAddOp(v, OP_IdxDelete, iCur+i, 0);
}
}