/*
** 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
** in order to generate code for DELETE FROM statements.
**
** $Id: delete.c,v 1.127 2006/06/19 03:05:10 danielk1977 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 *sqlite3SrcListLookup(Parse *pParse, SrcList *pSrc){
Table *pTab = 0;
int i;
struct SrcList_item *pItem;
for(i=0, pItem=pSrc->a; i<pSrc->nSrc; i++, pItem++){
pTab = sqlite3LocateTable(pParse, pItem->zName, pItem->zDatabase);
sqlite3DeleteTable(pParse->db, pItem->pTab);
pItem->pTab = pTab;
if( pTab ){
pTab->nRef++;
}
}
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 sqlite3IsReadOnly(Parse *pParse, Table *pTab, int viewOk){
if( (pTab->readOnly && (pParse->db->flags & SQLITE_WriteSchema)==0
&& pParse->nested==0)
#ifndef SQLITE_OMIT_VIRTUALTABLE
|| (pTab->pMod && pTab->pMod->pModule->xUpdate==0)
#endif
){
sqlite3ErrorMsg(pParse, "table %s may not be modified", pTab->zName);
return 1;
}
#ifndef SQLITE_OMIT_VIEW
if( !viewOk && pTab->pSelect ){
sqlite3ErrorMsg(pParse,"cannot modify %s because it is a view",pTab->zName);
return 1;
}
#endif
return 0;
}
/*
** Generate code that will open a table for reading.
*/
void sqlite3OpenTable(
Parse *p, /* Generate code into this VDBE */
int iCur, /* The cursor number of the table */
int iDb, /* The database index in sqlite3.aDb[] */
Table *pTab, /* The table to be opened */
int opcode /* OP_OpenRead or OP_OpenWrite */
){
Vdbe *v;
if( IsVirtual(pTab) ) return;
v = sqlite3GetVdbe(p);
assert( opcode==OP_OpenWrite || opcode==OP_OpenRead );
sqlite3TableLock(p, iDb, pTab->tnum, (opcode==OP_OpenWrite), pTab->zName);
sqlite3VdbeAddOp(v, OP_Integer, iDb, 0);
VdbeComment((v, "# %s", pTab->zName));
sqlite3VdbeAddOp(v, opcode, iCur, pTab->tnum);
sqlite3VdbeAddOp(v, OP_SetNumColumns, iCur, pTab->nCol);
}
/*
** Generate code for a DELETE FROM statement.
**
** DELETE FROM table_wxyz WHERE a<5 AND b NOT NULL;
** \________/ \________________/
** pTabList pWhere
*/
void sqlite3DeleteFrom(
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 = 0; /* 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 */
sqlite3 *db; /* Main database structure */
AuthContext sContext; /* Authorization context */
int oldIdx = -1; /* Cursor for the OLD table of AFTER triggers */
NameContext sNC; /* Name context to resolve expressions in */
int iDb;
#ifndef SQLITE_OMIT_TRIGGER
int isView; /* True if attempting to delete from a view */
int triggers_exist = 0; /* True if any triggers exist */
#endif
sContext.pParse = 0;
if( pParse->nErr || sqlite3MallocFailed() ){
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 = sqlite3SrcListLookup(pParse, pTabList);
if( pTab==0 ) goto delete_from_cleanup;
/* Figure out if we have any triggers and if the table being
** deleted from is a view
*/
#ifndef SQLITE_OMIT_TRIGGER
triggers_exist = sqlite3TriggersExist(pParse, pTab, TK_DELETE, 0);
isView = pTab->pSelect!=0;
#else
# define triggers_exist 0
# define isView 0
#endif
#ifdef SQLITE_OMIT_VIEW
# undef isView
# define isView 0
#endif
if( sqlite3IsReadOnly(pParse, pTab, triggers_exist) ){
goto delete_from_cleanup;
}
iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
assert( iDb<db->nDb );
zDb = db->aDb[iDb].zName;
if( sqlite3AuthCheck(pParse, SQLITE_DELETE, pTab->zName, 0, zDb) ){
goto delete_from_cleanup;
}
/* If pTab is really a view, make sure it has been initialized.
*/
if( sqlite3ViewGetColumnNames(pParse, pTab) ){
goto delete_from_cleanup;
}
/* Allocate a cursor used to store the old.* data for a trigger.
*/
if( triggers_exist ){
oldIdx = pParse->nTab++;
}
/* Resolve the column names in the WHERE clause.
*/
assert( pTabList->nSrc==1 );
iCur = pTabList->a[0].iCursor = pParse->nTab++;
memset(&sNC, 0, sizeof(sNC));
sNC.pParse = pParse;
sNC.pSrcList = pTabList;
if( sqlite3ExprResolveNames(&sNC, pWhere) ){
goto delete_from_cleanup;
}
/* Start the view context
*/
if( isView ){
sqlite3AuthContextPush(pParse, &sContext, pTab->zName);
}
/* Begin generating code.
*/
v = sqlite3GetVdbe(pParse);
if( v==0 ){
goto delete_from_cleanup;
}
if( pParse->nested==0 ) sqlite3VdbeCountChanges(v);
sqlite3BeginWriteOperation(pParse, triggers_exist, iDb);
/* If we are trying to delete from a view, realize that view into
** a ephemeral table.
*/
if( isView ){
Select *pView = sqlite3SelectDup(pTab->pSelect);
sqlite3Select(pParse, pView, SRT_EphemTab, iCur, 0, 0, 0, 0);
sqlite3SelectDelete(pView);
}
/* Initialize the counter of the number of rows deleted, if
** we are counting rows.
*/
if( db->flags & SQLITE_CountRows ){
sqlite3VdbeAddOp(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 && !triggers_exist && !IsVirtual(pTab) ){
if( db->flags & SQLITE_CountRows ){
/* If counting rows deleted, just count the total number of
** entries in the table. */
int endOfLoop = sqlite3VdbeMakeLabel(v);
int addr2;
if( !isView ){
sqlite3OpenTable(pParse, iCur, iDb, pTab, OP_OpenRead);
}
sqlite3VdbeAddOp(v, OP_Rewind, iCur, sqlite3VdbeCurrentAddr(v)+2);
addr2 = sqlite3VdbeAddOp(v, OP_AddImm, 1, 0);
sqlite3VdbeAddOp(v, OP_Next, iCur, addr2);
sqlite3VdbeResolveLabel(v, endOfLoop);
sqlite3VdbeAddOp(v, OP_Close, iCur, 0);
}
if( !isView ){
sqlite3VdbeAddOp(v, OP_Clear, pTab->tnum, iDb);
if( !pParse->nested ){
sqlite3VdbeChangeP3(v, -1, pTab->zName, P3_STATIC);
}
for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
assert( pIdx->pSchema==pTab->pSchema );
sqlite3VdbeAddOp(v, OP_Clear, pIdx->tnum, 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 = sqlite3WhereBegin(pParse, pTabList, pWhere, 0);
if( pWInfo==0 ) goto delete_from_cleanup;
/* Remember the rowid of every item to be deleted.
*/
sqlite3VdbeAddOp(v, IsVirtual(pTab) ? OP_VRowid : OP_Rowid, iCur, 0);
sqlite3VdbeAddOp(v, OP_FifoWrite, 0, 0);
if( db->flags & SQLITE_CountRows ){
sqlite3VdbeAddOp(v, OP_AddImm, 1, 0);
}
/* End the database scan loop.
*/
sqlite3WhereEnd(pWInfo);
/* Open the pseudo-table used to store OLD if there are triggers.
*/
if( triggers_exist ){
sqlite3VdbeAddOp(v, OP_OpenPseudo, oldIdx, 0);
sqlite3VdbeAddOp(v, OP_SetNumColumns, oldIdx, pTab->nCol);
}
/* 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.
*/
end = sqlite3VdbeMakeLabel(v);
/* This is the beginning of the delete loop when there are
** row triggers.
*/
if( triggers_exist ){
addr = sqlite3VdbeAddOp(v, OP_FifoRead, 0, end);
if( !isView ){
sqlite3VdbeAddOp(v, OP_Dup, 0, 0);
sqlite3OpenTable(pParse, iCur, iDb, pTab, OP_OpenRead);
}
sqlite3VdbeAddOp(v, OP_MoveGe, iCur, 0);
sqlite3VdbeAddOp(v, OP_Rowid, iCur, 0);
sqlite3VdbeAddOp(v, OP_RowData, iCur, 0);
sqlite3VdbeAddOp(v, OP_Insert, oldIdx, 0);
if( !isView ){
sqlite3VdbeAddOp(v, OP_Close, iCur, 0);
}
(void)sqlite3CodeRowTrigger(pParse, TK_DELETE, 0, TRIGGER_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_FifoRead 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.
*/
sqlite3OpenTableAndIndices(pParse, pTab, iCur, OP_OpenWrite);
/* This is the beginning of the delete loop when there are no
** row triggers */
if( !triggers_exist ){
addr = sqlite3VdbeAddOp(v, OP_FifoRead, 0, end);
}
/* Delete the row */
#ifndef SQLITE_OMIT_VIRTUALTABLE
if( IsVirtual(pTab) ){
pParse->pVirtualLock = pTab;
sqlite3VdbeOp3(v, OP_VUpdate, 0, 1, (const char*)pTab->pVtab, P3_VTAB);
}else
#endif
{
sqlite3GenerateRowDelete(db, v, pTab, iCur, pParse->nested==0);
}
}
/* If there are row triggers, close all cursors then invoke
** the AFTER triggers
*/
if( triggers_exist ){
if( !isView ){
for(i=1, pIdx=pTab->pIndex; pIdx; i++, pIdx=pIdx->pNext){
sqlite3VdbeAddOp(v, OP_Close, iCur + i, pIdx->tnum);
}
sqlite3VdbeAddOp(v, OP_Close, iCur, 0);
}
(void)sqlite3CodeRowTrigger(pParse, TK_DELETE, 0, TRIGGER_AFTER, pTab, -1,
oldIdx, (pParse->trigStack)?pParse->trigStack->orconf:OE_Default,
addr);
}
/* End of the delete loop */
sqlite3VdbeAddOp(v, OP_Goto, 0, addr);
sqlite3VdbeResolveLabel(v, end);
/* Close the cursors after the loop if there are no row triggers */
if( !triggers_exist && !IsVirtual(pTab) ){
for(i=1, pIdx=pTab->pIndex; pIdx; i++, pIdx=pIdx->pNext){
sqlite3VdbeAddOp(v, OP_Close, iCur + i, pIdx->tnum);
}
sqlite3VdbeAddOp(v, OP_Close, iCur, 0);
}
}
/*
** Return the number of rows that were deleted. If this routine is
** generating code because of a call to sqlite3NestedParse(), do not
** invoke the callback function.
*/
if( db->flags & SQLITE_CountRows && pParse->nested==0 && !pParse->trigStack ){
sqlite3VdbeAddOp(v, OP_Callback, 1, 0);
sqlite3VdbeSetNumCols(v, 1);
sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "rows deleted", P3_STATIC);
}
delete_from_cleanup:
sqlite3AuthContextPop(&sContext);
sqlite3SrcListDelete(pTabList);
sqlite3ExprDelete(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 sqlite3GenerateRowDelete(
sqlite3 *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 = sqlite3VdbeAddOp(v, OP_NotExists, iCur, 0);
sqlite3GenerateRowIndexDelete(v, pTab, iCur, 0);
sqlite3VdbeAddOp(v, OP_Delete, iCur, (count?OPFLAG_NCHANGE:0));
if( count ){
sqlite3VdbeChangeP3(v, -1, pTab->zName, P3_STATIC);
}
sqlite3VdbeJumpHere(v, addr);
}
/*
** 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 sqlite3GenerateRowIndexDelete(
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){
if( aIdxUsed!=0 && aIdxUsed[i-1]==0 ) continue;
sqlite3GenerateIndexKey(v, pIdx, iCur);
sqlite3VdbeAddOp(v, OP_IdxDelete, iCur+i, 0);
}
}
/*
** Generate code that will assemble an index key and put it on the top
** of the tack. The key with be for index pIdx which is an index on pTab.
** iCur is the index of a cursor open on the pTab table and pointing to
** the entry that needs indexing.
*/
void sqlite3GenerateIndexKey(
Vdbe *v, /* Generate code into this VDBE */
Index *pIdx, /* The index for which to generate a key */
int iCur /* Cursor number for the pIdx->pTable table */
){
int j;
Table *pTab = pIdx->pTable;
sqlite3VdbeAddOp(v, OP_Rowid, iCur, 0);
for(j=0; j<pIdx->nColumn; j++){
int idx = pIdx->aiColumn[j];
if( idx==pTab->iPKey ){
sqlite3VdbeAddOp(v, OP_Dup, j, 0);
}else{
sqlite3VdbeAddOp(v, OP_Column, iCur, idx);
sqlite3ColumnDefault(v, pTab, idx);
}
}
sqlite3VdbeAddOp(v, OP_MakeIdxRec, pIdx->nColumn, 0);
sqlite3IndexAffinityStr(v, pIdx);
}