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394 lines
13 KiB
394 lines
13 KiB
/*
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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 326789 2004-07-07 21:25:56Z pahlibar $
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*/
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#include "sqliteInt.h"
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/*
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** Look up every table that is named in pSrc. If any table is not found,
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** add an error message to pParse->zErrMsg and return NULL. If all tables
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** are found, return a pointer to the last table.
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*/
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Table *sqliteSrcListLookup(Parse *pParse, SrcList *pSrc){
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Table *pTab = 0;
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int i;
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for(i=0; i<pSrc->nSrc; i++){
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const char *zTab = pSrc->a[i].zName;
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const char *zDb = pSrc->a[i].zDatabase;
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pTab = sqliteLocateTable(pParse, zTab, zDb);
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pSrc->a[i].pTab = pTab;
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}
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return pTab;
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}
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/*
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** Check to make sure the given table is writable. If it is not
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** writable, generate an error message and return 1. If it is
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** writable return 0;
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*/
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int sqliteIsReadOnly(Parse *pParse, Table *pTab, int viewOk){
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if( pTab->readOnly ){
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sqliteErrorMsg(pParse, "table %s may not be modified", pTab->zName);
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return 1;
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}
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if( !viewOk && pTab->pSelect ){
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sqliteErrorMsg(pParse, "cannot modify %s because it is a view",pTab->zName);
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return 1;
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}
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return 0;
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}
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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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SrcList *pTabList, /* 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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const char *zDb; /* Name of database holding pTab */
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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 iCur; /* VDBE Cursor number for pTab */
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sqlite *db; /* Main database structure */
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int isView; /* True if attempting to delete from a view */
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AuthContext sContext; /* Authorization context */
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int row_triggers_exist = 0; /* True if any triggers exist */
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int before_triggers; /* True if there are BEFORE triggers */
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int after_triggers; /* True if there are AFTER triggers */
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int oldIdx = -1; /* Cursor for the OLD table of AFTER triggers */
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sContext.pParse = 0;
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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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assert( pTabList->nSrc==1 );
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/* Locate the table which we want to delete. This table has to be
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** put in an SrcList 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 SrcList* parameter instead of just a Table* parameter.
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*/
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pTab = sqliteSrcListLookup(pParse, pTabList);
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if( pTab==0 ) goto delete_from_cleanup;
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before_triggers = sqliteTriggersExist(pParse, pTab->pTrigger,
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TK_DELETE, TK_BEFORE, TK_ROW, 0);
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after_triggers = sqliteTriggersExist(pParse, pTab->pTrigger,
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TK_DELETE, TK_AFTER, TK_ROW, 0);
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row_triggers_exist = before_triggers || after_triggers;
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isView = pTab->pSelect!=0;
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if( sqliteIsReadOnly(pParse, pTab, before_triggers) ){
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goto delete_from_cleanup;
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}
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assert( pTab->iDb<db->nDb );
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zDb = db->aDb[pTab->iDb].zName;
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if( sqliteAuthCheck(pParse, SQLITE_DELETE, pTab->zName, 0, zDb) ){
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goto delete_from_cleanup;
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}
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/* If pTab is really a view, make sure it has been initialized.
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*/
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if( isView && sqliteViewGetColumnNames(pParse, pTab) ){
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goto delete_from_cleanup;
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}
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/* Allocate a cursor used to store the old.* data for a trigger.
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*/
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if( row_triggers_exist ){
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oldIdx = pParse->nTab++;
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}
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/* Resolve the column names in all the expressions.
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*/
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assert( pTabList->nSrc==1 );
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iCur = pTabList->a[0].iCursor = pParse->nTab++;
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if( pWhere ){
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if( sqliteExprResolveIds(pParse, pTabList, 0, 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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/* Start the view context
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*/
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if( isView ){
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sqliteAuthContextPush(pParse, &sContext, pTab->zName);
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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 ){
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goto delete_from_cleanup;
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}
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sqliteBeginWriteOperation(pParse, row_triggers_exist, pTab->iDb);
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/* If we are trying to delete from a view, construct that view into
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** a temporary table.
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*/
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if( isView ){
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Select *pView = sqliteSelectDup(pTab->pSelect);
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sqliteSelect(pParse, pView, SRT_TempTable, iCur, 0, 0, 0);
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sqliteSelectDelete(pView);
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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. Note, however, that
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** this means that the row change count will be incorrect.
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*/
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if( pWhere==0 && !row_triggers_exist ){
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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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if( !isView ){
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sqliteVdbeAddOp(v, OP_Integer, pTab->iDb, 0);
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sqliteVdbeAddOp(v, OP_OpenRead, iCur, pTab->tnum);
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}
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sqliteVdbeAddOp(v, OP_Rewind, iCur, sqliteVdbeCurrentAddr(v)+2);
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addr = sqliteVdbeAddOp(v, OP_AddImm, 1, 0);
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sqliteVdbeAddOp(v, OP_Next, iCur, addr);
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sqliteVdbeResolveLabel(v, endOfLoop);
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sqliteVdbeAddOp(v, OP_Close, iCur, 0);
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}
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if( !isView ){
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sqliteVdbeAddOp(v, OP_Clear, pTab->tnum, pTab->iDb);
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for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
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sqliteVdbeAddOp(v, OP_Clear, pIdx->tnum, pIdx->iDb);
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}
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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 and 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, 0);
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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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/* Open the pseudo-table used to store OLD if there are triggers.
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*/
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if( row_triggers_exist ){
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sqliteVdbeAddOp(v, OP_OpenPseudo, oldIdx, 0);
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}
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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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sqliteVdbeAddOp(v, OP_ListRewind, 0, 0);
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end = sqliteVdbeMakeLabel(v);
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/* This is the beginning of the delete loop when there are
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** row triggers.
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*/
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if( row_triggers_exist ){
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addr = sqliteVdbeAddOp(v, OP_ListRead, 0, end);
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sqliteVdbeAddOp(v, OP_Dup, 0, 0);
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if( !isView ){
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sqliteVdbeAddOp(v, OP_Integer, pTab->iDb, 0);
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sqliteVdbeAddOp(v, OP_OpenRead, iCur, pTab->tnum);
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}
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sqliteVdbeAddOp(v, OP_MoveTo, iCur, 0);
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sqliteVdbeAddOp(v, OP_Recno, iCur, 0);
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sqliteVdbeAddOp(v, OP_RowData, iCur, 0);
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sqliteVdbeAddOp(v, OP_PutIntKey, oldIdx, 0);
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if( !isView ){
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sqliteVdbeAddOp(v, OP_Close, iCur, 0);
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}
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sqliteCodeRowTrigger(pParse, TK_DELETE, 0, TK_BEFORE, pTab, -1,
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oldIdx, (pParse->trigStack)?pParse->trigStack->orconf:OE_Default,
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addr);
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}
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if( !isView ){
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/* Open cursors for the table we are deleting from and all its
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** indices. If there are row triggers, this happens inside the
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** OP_ListRead loop because the cursor have to all be closed
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** before the trigger fires. If there are no row triggers, the
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** cursors are opened only once on the outside the loop.
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*/
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pParse->nTab = iCur + 1;
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sqliteOpenTableAndIndices(pParse, pTab, iCur);
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/* This is the beginning of the delete loop when there are no
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** row triggers */
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if( !row_triggers_exist ){
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addr = sqliteVdbeAddOp(v, OP_ListRead, 0, end);
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}
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/* Delete the row */
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sqliteGenerateRowDelete(db, v, pTab, iCur, pParse->trigStack==0);
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}
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/* If there are row triggers, close all cursors then invoke
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** the AFTER triggers
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*/
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if( row_triggers_exist ){
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if( !isView ){
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for(i=1, pIdx=pTab->pIndex; pIdx; i++, pIdx=pIdx->pNext){
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sqliteVdbeAddOp(v, OP_Close, iCur + i, pIdx->tnum);
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}
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sqliteVdbeAddOp(v, OP_Close, iCur, 0);
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}
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sqliteCodeRowTrigger(pParse, TK_DELETE, 0, TK_AFTER, pTab, -1,
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oldIdx, (pParse->trigStack)?pParse->trigStack->orconf:OE_Default,
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addr);
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}
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/* End of the delete loop */
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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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/* Close the cursors after the loop if there are no row triggers */
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if( !row_triggers_exist ){
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for(i=1, pIdx=pTab->pIndex; pIdx; i++, pIdx=pIdx->pNext){
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sqliteVdbeAddOp(v, OP_Close, iCur + i, pIdx->tnum);
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}
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sqliteVdbeAddOp(v, OP_Close, iCur, 0);
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pParse->nTab = iCur;
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}
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}
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sqliteVdbeAddOp(v, OP_SetCounts, 0, 0);
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sqliteEndWriteOperation(pParse);
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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_ColumnName, 0, 1);
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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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sqliteAuthContextPop(&sContext);
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sqliteSrcListDelete(pTabList);
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sqliteExprDelete(pWhere);
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return;
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}
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/*
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** This routine generates VDBE code that causes a single row of a
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** single table to be deleted.
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**
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** The VDBE must be in a particular state when this routine is called.
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** These are the requirements:
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**
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** 1. A read/write cursor pointing to pTab, the table containing the row
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** to be deleted, must be opened as cursor number "base".
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**
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** 2. Read/write cursors for all indices of pTab must be open as
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** cursor number base+i for the i-th index.
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**
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** 3. The record number of the row to be deleted must be on the top
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** of the stack.
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**
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** This routine pops the top of the stack to remove the record number
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** and then generates code to remove both the table record and all index
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** entries that point to that record.
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*/
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void sqliteGenerateRowDelete(
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sqlite *db, /* The database containing the index */
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Vdbe *v, /* Generate code into this VDBE */
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Table *pTab, /* Table containing the row to be deleted */
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int iCur, /* Cursor number for the table */
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int count /* Increment the row change counter */
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){
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int addr;
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addr = sqliteVdbeAddOp(v, OP_NotExists, iCur, 0);
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sqliteGenerateRowIndexDelete(db, v, pTab, iCur, 0);
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sqliteVdbeAddOp(v, OP_Delete, iCur,
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(count?OPFLAG_NCHANGE:0) | OPFLAG_CSCHANGE);
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sqliteVdbeChangeP2(v, addr, sqliteVdbeCurrentAddr(v));
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}
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/*
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** This routine generates VDBE code that causes the deletion of all
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** index entries associated with a single row of a single table.
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**
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** The VDBE must be in a particular state when this routine is called.
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** These are the requirements:
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**
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** 1. A read/write cursor pointing to pTab, the table containing the row
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** to be deleted, must be opened as cursor number "iCur".
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**
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** 2. Read/write cursors for all indices of pTab must be open as
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** cursor number iCur+i for the i-th index.
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**
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** 3. The "iCur" cursor must be pointing to the row that is to be
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** deleted.
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*/
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void sqliteGenerateRowIndexDelete(
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sqlite *db, /* The database containing the index */
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Vdbe *v, /* Generate code into this VDBE */
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Table *pTab, /* Table containing the row to be deleted */
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int iCur, /* Cursor number for the table */
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char *aIdxUsed /* Only delete if aIdxUsed!=0 && aIdxUsed[i]!=0 */
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){
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int i;
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Index *pIdx;
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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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if( aIdxUsed!=0 && aIdxUsed[i-1]==0 ) continue;
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sqliteVdbeAddOp(v, OP_Recno, iCur, 0);
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for(j=0; j<pIdx->nColumn; j++){
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int idx = pIdx->aiColumn[j];
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if( idx==pTab->iPKey ){
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sqliteVdbeAddOp(v, OP_Dup, j, 0);
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}else{
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sqliteVdbeAddOp(v, OP_Column, iCur, idx);
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}
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}
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sqliteVdbeAddOp(v, OP_MakeIdxKey, pIdx->nColumn, 0);
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if( db->file_format>=4 ) sqliteAddIdxKeyType(v, pIdx);
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sqliteVdbeAddOp(v, OP_IdxDelete, iCur+i, 0);
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}
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}
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