src/delete.c

   1 /*
   2 ** 2001 September 15
   3 **
   4 ** The author disclaims copyright to this source code.  In place of
   5 ** a legal notice, here is a blessing:
   6 **
   7 **    May you do good and not evil.
   8 **    May you find forgiveness for yourself and forgive others.
   9 **    May you share freely, never taking more than you give.
  10 **
  11 *************************************************************************
  12 ** This file contains C code routines that are called by the parser
  13 ** in order to generate code for DELETE FROM statements.
  14 */
  15 #include "sqliteInt.h"
  16
  17 /*
  18 ** While a SrcList can in general represent multiple tables and subqueries
  19 ** (as in the FROM clause of a SELECT statement) in this case it contains
  20 ** the name of a single table, as one might find in an INSERT, DELETE,
  21 ** or UPDATE statement.  Look up that table in the symbol table and
  22 ** return a pointer.  Set an error message and return NULL if the table
  23 ** name is not found or if any other error occurs.
  24 **
  25 ** The following fields are initialized appropriate in pSrc:
  26 **
  27 **    pSrc->a[0].pTab       Pointer to the Table object
  28 **    pSrc->a[0].pIndex     Pointer to the INDEXED BY index, if there is one
  29 **
  30 */
  31 Table *sqlite3SrcListLookup(Parse *pParse, SrcList *pSrc){
  32   struct SrcList_item *pItem = pSrc->a;
  33   Table *pTab;
  34   assert( pItem && pSrc->nSrc==1 );
  35   pTab = sqlite3LocateTable(pParse, 0, pItem->zName, pItem->zDatabase);
  36   sqlite3DeleteTable(pParse->db, pItem->pTab);
  37   pItem->pTab = pTab;
  38   if( pTab ){
  39     pTab->nRef++;
  40   }
  41   if( sqlite3IndexedByLookup(pParse, pItem) ){
  42     pTab = 0;
  43   }
  44   return pTab;
  45 }
  46
  47 /*
  48 ** Check to make sure the given table is writable.  If it is not
  49 ** writable, generate an error message and return 1.  If it is
  50 ** writable return 0;
  51 */
  52 int sqlite3IsReadOnly(Parse *pParse, Table *pTab, int viewOk){
  53   /* A table is not writable under the following circumstances:
  54   **
  55   **   1) It is a virtual table and no implementation of the xUpdate method
  56   **      has been provided, or
  57   **   2) It is a system table (i.e. sqlite_master), this call is not
  58   **      part of a nested parse and writable_schema pragma has not
  59   **      been specified.
  60   **
  61   ** In either case leave an error message in pParse and return non-zero.
  62   */
  63   if( ( IsVirtual(pTab)
  64      && sqlite3GetVTable(pParse->db, pTab)->pMod->pModule->xUpdate==0 )
  65    || ( (pTab->tabFlags & TF_Readonly)!=0
  66      && (pParse->db->flags & SQLITE_WriteSchema)==0
  67      && pParse->nested==0 )
  68   ){
  69     sqlite3ErrorMsg(pParse, "table %s may not be modified", pTab->zName);
  70     return 1;
  71   }
  72
  73 #ifndef SQLITE_OMIT_VIEW
  74   if( !viewOk && pTab->pSelect ){
  75     sqlite3ErrorMsg(pParse,"cannot modify %s because it is a view",pTab->zName);
  76     return 1;
  77   }
  78 #endif
  79   return 0;
  80 }
  81
  82
  83 #if !defined(SQLITE_OMIT_VIEW) && !defined(SQLITE_OMIT_TRIGGER)
  84 /*
  85 ** Evaluate a view and store its result in an ephemeral table.  The
  86 ** pWhere argument is an optional WHERE clause that restricts the
  87 ** set of rows in the view that are to be added to the ephemeral table.
  88 */
  89 void sqlite3MaterializeView(
  90   Parse *pParse,       /* Parsing context */
  91   Table *pView,        /* View definition */
  92   Expr *pWhere,        /* Optional WHERE clause to be added */
  93   int iCur             /* Cursor number for ephemerial table */
  94 ){
  95   SelectDest dest;
  96   Select *pDup;
  97   sqlite3 *db = pParse->db;
  98
  99   pDup = sqlite3SelectDup(db, pView->pSelect, 0);
 100   if( pWhere ){
 101     SrcList *pFrom;
 102
 103     pWhere = sqlite3ExprDup(db, pWhere, 0);
 104     pFrom = sqlite3SrcListAppend(db, 0, 0, 0);
 105     if( pFrom ){
 106       assert( pFrom->nSrc==1 );
 107       pFrom->a[0].zAlias = sqlite3DbStrDup(db, pView->zName);
 108       pFrom->a[0].pSelect = pDup;
 109       assert( pFrom->a[0].pOn==0 );
 110       assert( pFrom->a[0].pUsing==0 );
 111     }else{
 112       sqlite3SelectDelete(db, pDup);
 113     }
 114     pDup = sqlite3SelectNew(pParse, 0, pFrom, pWhere, 0, 0, 0, 0, 0, 0);
 115   }
 116   sqlite3SelectDestInit(&dest, SRT_EphemTab, iCur);
 117   sqlite3Select(pParse, pDup, &dest);
 118   sqlite3SelectDelete(db, pDup);
 119 }
 120 #endif /* !defined(SQLITE_OMIT_VIEW) && !defined(SQLITE_OMIT_TRIGGER) */
 121
 122 #if defined(SQLITE_ENABLE_UPDATE_DELETE_LIMIT) && !defined(SQLITE_OMIT_SUBQUERY)
 123 /*
 124 ** Generate an expression tree to implement the WHERE, ORDER BY,
 125 ** and LIMIT/OFFSET portion of DELETE and UPDATE statements.
 126 **
 127 **     DELETE FROM table_wxyz WHERE a<5 ORDER BY a LIMIT 1;
 128 **                            \__________________________/
 129 **                               pLimitWhere (pInClause)
 130 */
 131 Expr *sqlite3LimitWhere(
 132   Parse *pParse,               /* The parser context */
 133   SrcList *pSrc,               /* the FROM clause -- which tables to scan */
 134   Expr *pWhere,                /* The WHERE clause.  May be null */
 135   ExprList *pOrderBy,          /* The ORDER BY clause.  May be null */
 136   Expr *pLimit,                /* The LIMIT clause.  May be null */
 137   Expr *pOffset,               /* The OFFSET clause.  May be null */
 138   char *zStmtType              /* Either DELETE or UPDATE.  For error messages. */
 139 ){
 140   Expr *pWhereRowid = NULL;    /* WHERE rowid .. */
 141   Expr *pInClause = NULL;      /* WHERE rowid IN ( select ) */
 142   Expr *pSelectRowid = NULL;   /* SELECT rowid ... */
 143   ExprList *pEList = NULL;     /* Expression list contaning only pSelectRowid */
 144   SrcList *pSelectSrc = NULL;  /* SELECT rowid FROM x ... (dup of pSrc) */
 145   Select *pSelect = NULL;      /* Complete SELECT tree */
 146
 147   /* Check that there isn't an ORDER BY without a LIMIT clause.
 148   */
 149   if( pOrderBy && (pLimit == 0) ) {
 150     sqlite3ErrorMsg(pParse, "ORDER BY without LIMIT on %s", zStmtType);
 151     goto limit_where_cleanup_2;
 152   }
 153
 154   /* We only need to generate a select expression if there
 155   ** is a limit/offset term to enforce.
 156   */
 157   if( pLimit == 0 ) {
 158     /* if pLimit is null, pOffset will always be null as well. */
 159     assert( pOffset == 0 );
 160     return pWhere;
 161   }
 162
 163   /* Generate a select expression tree to enforce the limit/offset
 164   ** term for the DELETE or UPDATE statement.  For example:
 165   **   DELETE FROM table_a WHERE col1=1 ORDER BY col2 LIMIT 1 OFFSET 1
 166   ** becomes:
 167   **   DELETE FROM table_a WHERE rowid IN (
 168   **     SELECT rowid FROM table_a WHERE col1=1 ORDER BY col2 LIMIT 1 OFFSET 1
 169   **   );
 170   */
 171
 172   pSelectRowid = sqlite3PExpr(pParse, TK_ROW, 0, 0, 0);
 173   if( pSelectRowid == 0 ) goto limit_where_cleanup_2;
 174   pEList = sqlite3ExprListAppend(pParse, 0, pSelectRowid);
 175   if( pEList == 0 ) goto limit_where_cleanup_2;
 176
 177   /* duplicate the FROM clause as it is needed by both the DELETE/UPDATE tree
 178   ** and the SELECT subtree. */
 179   pSelectSrc = sqlite3SrcListDup(pParse->db, pSrc, 0);
 180   if( pSelectSrc == 0 ) {
 181     sqlite3ExprListDelete(pParse->db, pEList);
 182     goto limit_where_cleanup_2;
 183   }
 184
 185   /* generate the SELECT expression tree. */
 186   pSelect = sqlite3SelectNew(pParse,pEList,pSelectSrc,pWhere,0,0,
 187                              pOrderBy,0,pLimit,pOffset);
 188   if( pSelect == 0 ) return 0;
 189
 190   /* now generate the new WHERE rowid IN clause for the DELETE/UDPATE */
 191   pWhereRowid = sqlite3PExpr(pParse, TK_ROW, 0, 0, 0);
 192   if( pWhereRowid == 0 ) goto limit_where_cleanup_1;
 193   pInClause = sqlite3PExpr(pParse, TK_IN, pWhereRowid, 0, 0);
 194   if( pInClause == 0 ) goto limit_where_cleanup_1;
 195
 196   pInClause->x.pSelect = pSelect;
 197   pInClause->flags |= EP_xIsSelect;
 198   sqlite3ExprSetHeight(pParse, pInClause);
 199   return pInClause;
 200
 201   /* something went wrong. clean up anything allocated. */
 202 limit_where_cleanup_1:
 203   sqlite3SelectDelete(pParse->db, pSelect);
 204   return 0;
 205
 206 limit_where_cleanup_2:
 207   sqlite3ExprDelete(pParse->db, pWhere);
 208   sqlite3ExprListDelete(pParse->db, pOrderBy);
 209   sqlite3ExprDelete(pParse->db, pLimit);
 210   sqlite3ExprDelete(pParse->db, pOffset);
 211   return 0;
 212 }
 213 #endif /* defined(SQLITE_ENABLE_UPDATE_DELETE_LIMIT) && !defined(SQLITE_OMIT_SUBQUERY) */
 214
 215 /*
 216 ** Generate code for a DELETE FROM statement.
 217 **
 218 **     DELETE FROM table_wxyz WHERE a<5 AND b NOT NULL;
 219 **                 \________/       \________________/
 220 **                  pTabList              pWhere
 221 */
 222 void sqlite3DeleteFrom(
 223   Parse *pParse,         /* The parser context */
 224   SrcList *pTabList,     /* The table from which we should delete things */
 225   Expr *pWhere           /* The WHERE clause.  May be null */
 226 ){
 227   Vdbe *v;               /* The virtual database engine */
 228   Table *pTab;           /* The table from which records will be deleted */
 229   const char *zDb;       /* Name of database holding pTab */
 230   int end, addr = 0;     /* A couple addresses of generated code */
 231   int i;                 /* Loop counter */
 232   WhereInfo *pWInfo;     /* Information about the WHERE clause */
 233   Index *pIdx;           /* For looping over indices of the table */
 234   int iCur;              /* VDBE Cursor number for pTab */
 235   sqlite3 *db;           /* Main database structure */
 236   AuthContext sContext;  /* Authorization context */
 237   NameContext sNC;       /* Name context to resolve expressions in */
 238   int iDb;               /* Database number */
 239   int memCnt = -1;       /* Memory cell used for change counting */
 240   int rcauth;            /* Value returned by authorization callback */
 241
 242 #ifndef SQLITE_OMIT_TRIGGER
 243   int isView;                  /* True if attempting to delete from a view */
 244   Trigger *pTrigger;           /* List of table triggers, if required */
 245 #endif
 246
 247   memset(&sContext, 0, sizeof(sContext));
 248   db = pParse->db;
 249   if( pParse->nErr || db->mallocFailed ){
 250     goto delete_from_cleanup;
 251   }
 252   assert( pTabList->nSrc==1 );
 253
 254   /* Locate the table which we want to delete.  This table has to be
 255   ** put in an SrcList structure because some of the subroutines we
 256   ** will be calling are designed to work with multiple tables and expect
 257   ** an SrcList* parameter instead of just a Table* parameter.
 258   */
 259   pTab = sqlite3SrcListLookup(pParse, pTabList);
 260   if( pTab==0 )  goto delete_from_cleanup;
 261
 262   /* Figure out if we have any triggers and if the table being
 263   ** deleted from is a view
 264   */
 265 #ifndef SQLITE_OMIT_TRIGGER
 266   pTrigger = sqlite3TriggersExist(pParse, pTab, TK_DELETE, 0, 0);
 267   isView = pTab->pSelect!=0;
 268 #else
 269 # define pTrigger 0
 270 # define isView 0
 271 #endif
 272 #ifdef SQLITE_OMIT_VIEW
 273 # undef isView
 274 # define isView 0
 275 #endif
 276
 277   /* If pTab is really a view, make sure it has been initialized.
 278   */
 279   if( sqlite3ViewGetColumnNames(pParse, pTab) ){
 280     goto delete_from_cleanup;
 281   }
 282
 283   if( sqlite3IsReadOnly(pParse, pTab, (pTrigger?1:0)) ){
 284     goto delete_from_cleanup;
 285   }
 286   iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
 287   assert( iDb<db->nDb );
 288   zDb = db->aDb[iDb].zName;
 289   rcauth = sqlite3AuthCheck(pParse, SQLITE_DELETE, pTab->zName, 0, zDb);
 290   assert( rcauth==SQLITE_OK || rcauth==SQLITE_DENY || rcauth==SQLITE_IGNORE );
 291   if( rcauth==SQLITE_DENY ){
 292     goto delete_from_cleanup;
 293   }
 294   assert(!isView || pTrigger);
 295
 296   /* Assign  cursor number to the table and all its indices.
 297   */
 298   assert( pTabList->nSrc==1 );
 299   iCur = pTabList->a[0].iCursor = pParse->nTab++;
 300   for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
 301     pParse->nTab++;
 302   }
 303
 304   /* Start the view context
 305   */
 306   if( isView ){
 307     sqlite3AuthContextPush(pParse, &sContext, pTab->zName);
 308   }
 309
 310   /* Begin generating code.
 311   */
 312   v = sqlite3GetVdbe(pParse);
 313   if( v==0 ){
 314     goto delete_from_cleanup;
 315   }
 316   if( pParse->nested==0 ) sqlite3VdbeCountChanges(v);
 317   sqlite3BeginWriteOperation(pParse, 1, iDb);
 318
 319   /* If we are trying to delete from a view, realize that view into
 320   ** a ephemeral table.
 321   */
 322 #if !defined(SQLITE_OMIT_VIEW) && !defined(SQLITE_OMIT_TRIGGER)
 323   if( isView ){
 324     sqlite3MaterializeView(pParse, pTab, pWhere, iCur);
 325   }
 326 #endif
 327
 328   /* Resolve the column names in the WHERE clause.
 329   */
 330   memset(&sNC, 0, sizeof(sNC));
 331   sNC.pParse = pParse;
 332   sNC.pSrcList = pTabList;
 333   if( sqlite3ResolveExprNames(&sNC, pWhere) ){
 334     goto delete_from_cleanup;
 335   }
 336
 337   /* Initialize the counter of the number of rows deleted, if
 338   ** we are counting rows.
 339   */
 340   if( db->flags & SQLITE_CountRows ){
 341     memCnt = ++pParse->nMem;
 342     sqlite3VdbeAddOp2(v, OP_Integer, 0, memCnt);
 343   }
 344
 345 #ifndef SQLITE_OMIT_TRUNCATE_OPTIMIZATION
 346   /* Special case: A DELETE without a WHERE clause deletes everything.
 347   ** It is easier just to erase the whole table. Prior to version 3.6.5,
 348   ** this optimization caused the row change count (the value returned by
 349   ** API function sqlite3_count_changes) to be set incorrectly.  */
 350   if( rcauth==SQLITE_OK && pWhere==0 && !pTrigger && !IsVirtual(pTab)
 351    && 0==sqlite3FkRequired(pParse, pTab, 0, 0)
 352   ){
 353     assert( !isView );
 354     sqlite3VdbeAddOp4(v, OP_Clear, pTab->tnum, iDb, memCnt,
 355                       pTab->zName, P4_STATIC);
 356     for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
 357       assert( pIdx->pSchema==pTab->pSchema );
 358       sqlite3VdbeAddOp2(v, OP_Clear, pIdx->tnum, iDb);
 359     }
 360   }else
 361 #endif /* SQLITE_OMIT_TRUNCATE_OPTIMIZATION */
 362   /* The usual case: There is a WHERE clause so we have to scan through
 363   ** the table and pick which records to delete.
 364   */
 365   {
 366     int iRowSet = ++pParse->nMem;   /* Register for rowset of rows to delete */
 367     int iRowid = ++pParse->nMem;    /* Used for storing rowid values. */
 368     int regRowid;                   /* Actual register containing rowids */
 369
 370     /* Collect rowids of every row to be deleted.
 371     */
 372     sqlite3VdbeAddOp2(v, OP_Null, 0, iRowSet);
 373     pWInfo = sqlite3WhereBegin(
 374         pParse, pTabList, pWhere, 0, 0, WHERE_DUPLICATES_OK
 375     );
 376     if( pWInfo==0 ) goto delete_from_cleanup;
 377     regRowid = sqlite3ExprCodeGetColumn(pParse, pTab, -1, iCur, iRowid, 0);
 378     sqlite3VdbeAddOp2(v, OP_RowSetAdd, iRowSet, regRowid);
 379     if( db->flags & SQLITE_CountRows ){
 380       sqlite3VdbeAddOp2(v, OP_AddImm, memCnt, 1);
 381     }
 382     sqlite3WhereEnd(pWInfo);
 383
 384     /* Delete every item whose key was written to the list during the
 385     ** database scan.  We have to delete items after the scan is complete
 386     ** because deleting an item can change the scan order.  */
 387     end = sqlite3VdbeMakeLabel(v);
 388
 389     /* Unless this is a view, open cursors for the table we are
 390     ** deleting from and all its indices. If this is a view, then the
 391     ** only effect this statement has is to fire the INSTEAD OF
 392     ** triggers.  */
 393     if( !isView ){
 394       sqlite3OpenTableAndIndices(pParse, pTab, iCur, OP_OpenWrite);
 395     }
 396
 397     addr = sqlite3VdbeAddOp3(v, OP_RowSetRead, iRowSet, end, iRowid);
 398
 399     /* Delete the row */
 400 #ifndef SQLITE_OMIT_VIRTUALTABLE
 401     if( IsVirtual(pTab) ){
 402       const char *pVTab = (const char *)sqlite3GetVTable(db, pTab);
 403       sqlite3VtabMakeWritable(pParse, pTab);
 404       sqlite3VdbeAddOp4(v, OP_VUpdate, 0, 1, iRowid, pVTab, P4_VTAB);
 405       sqlite3VdbeChangeP5(v, OE_Abort);
 406       sqlite3MayAbort(pParse);
 407     }else
 408 #endif
 409     {
 410       int count = (pParse->nested==0);    /* True to count changes */
 411       sqlite3GenerateRowDelete(pParse, pTab, iCur, iRowid, count, pTrigger, OE_Default);
 412     }
 413
 414     /* End of the delete loop */
 415     sqlite3VdbeAddOp2(v, OP_Goto, 0, addr);
 416     sqlite3VdbeResolveLabel(v, end);
 417
 418     /* Close the cursors open on the table and its indexes. */
 419     if( !isView && !IsVirtual(pTab) ){
 420       for(i=1, pIdx=pTab->pIndex; pIdx; i++, pIdx=pIdx->pNext){
 421         sqlite3VdbeAddOp2(v, OP_Close, iCur + i, pIdx->tnum);
 422       }
 423       sqlite3VdbeAddOp1(v, OP_Close, iCur);
 424     }
 425   }
 426
 427   /* Update the sqlite_sequence table by storing the content of the
 428   ** maximum rowid counter values recorded while inserting into
 429   ** autoincrement tables.
 430   */
 431   if( pParse->nested==0 && pParse->pTriggerTab==0 ){
 432     sqlite3AutoincrementEnd(pParse);
 433   }
 434
 435   /* Return the number of rows that were deleted. If this routine is
 436   ** generating code because of a call to sqlite3NestedParse(), do not
 437   ** invoke the callback function.
 438   */
 439   if( (db->flags&SQLITE_CountRows) && !pParse->nested && !pParse->pTriggerTab ){
 440     sqlite3VdbeAddOp2(v, OP_ResultRow, memCnt, 1);
 441     sqlite3VdbeSetNumCols(v, 1);
 442     sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "rows deleted", SQLITE_STATIC);
 443   }
 444
 445 delete_from_cleanup:
 446   sqlite3AuthContextPop(&sContext);
 447   sqlite3SrcListDelete(db, pTabList);
 448   sqlite3ExprDelete(db, pWhere);
 449   return;
 450 }
 451 /* Make sure "isView" and other macros defined above are undefined. Otherwise
 452 ** thely may interfere with compilation of other functions in this file
 453 ** (or in another file, if this file becomes part of the amalgamation).  */
 454 #ifdef isView
 455  #undef isView
 456 #endif
 457 #ifdef pTrigger
 458  #undef pTrigger
 459 #endif
 460
 461 /*
 462 ** This routine generates VDBE code that causes a single row of a
 463 ** single table to be deleted.
 464 **
 465 ** The VDBE must be in a particular state when this routine is called.
 466 ** These are the requirements:
 467 **
 468 **   1.  A read/write cursor pointing to pTab, the table containing the row
 469 **       to be deleted, must be opened as cursor number $iCur.
 470 **
 471 **   2.  Read/write cursors for all indices of pTab must be open as
 472 **       cursor number base+i for the i-th index.
 473 **
 474 **   3.  The record number of the row to be deleted must be stored in
 475 **       memory cell iRowid.
 476 **
 477 ** This routine generates code to remove both the table record and all
 478 ** index entries that point to that record.
 479 */
 480 void sqlite3GenerateRowDelete(
 481   Parse *pParse,     /* Parsing context */
 482   Table *pTab,       /* Table containing the row to be deleted */
 483   int iCur,          /* Cursor number for the table */
 484   int iRowid,        /* Memory cell that contains the rowid to delete */
 485   int count,         /* If non-zero, increment the row change counter */
 486   Trigger *pTrigger, /* List of triggers to (potentially) fire */
 487   int onconf         /* Default ON CONFLICT policy for triggers */
 488 ){
 489   Vdbe *v = pParse->pVdbe;        /* Vdbe */
 490   int iOld = 0;                   /* First register in OLD.* array */
 491   int iLabel;                     /* Label resolved to end of generated code */
 492
 493   /* Vdbe is guaranteed to have been allocated by this stage. */
 494   assert( v );
 495
 496   /* Seek cursor iCur to the row to delete. If this row no longer exists
 497   ** (this can happen if a trigger program has already deleted it), do
 498   ** not attempt to delete it or fire any DELETE triggers.  */
 499   iLabel = sqlite3VdbeMakeLabel(v);
 500   sqlite3VdbeAddOp3(v, OP_NotExists, iCur, iLabel, iRowid);
 501
 502   /* If there are any triggers to fire, allocate a range of registers to
 503   ** use for the old.* references in the triggers.  */
 504   if( sqlite3FkRequired(pParse, pTab, 0, 0) || pTrigger ){
 505     u32 mask;                     /* Mask of OLD.* columns in use */
 506     int iCol;                     /* Iterator used while populating OLD.* */
 507
 508     /* TODO: Could use temporary registers here. Also could attempt to
 509     ** avoid copying the contents of the rowid register.  */
 510     mask = sqlite3TriggerColmask(
 511         pParse, pTrigger, 0, 0, TRIGGER_BEFORE|TRIGGER_AFTER, pTab, onconf
 512     );
 513     mask |= sqlite3FkOldmask(pParse, pTab);
 514     iOld = pParse->nMem+1;
 515     pParse->nMem += (1 + pTab->nCol);
 516
 517     /* Populate the OLD.* pseudo-table register array. These values will be
 518     ** used by any BEFORE and AFTER triggers that exist.  */
 519     sqlite3VdbeAddOp2(v, OP_Copy, iRowid, iOld);
 520     for(iCol=0; iCol<pTab->nCol; iCol++){
 521       if( mask==0xffffffff || mask&(1<<iCol) ){
 522         sqlite3ExprCodeGetColumnOfTable(v, pTab, iCur, iCol, iOld+iCol+1);
 523       }
 524     }
 525
 526     /* Invoke BEFORE DELETE trigger programs. */
 527     sqlite3CodeRowTrigger(pParse, pTrigger,
 528         TK_DELETE, 0, TRIGGER_BEFORE, pTab, iOld, onconf, iLabel
 529     );
 530
 531     /* Seek the cursor to the row to be deleted again. It may be that
 532     ** the BEFORE triggers coded above have already removed the row
 533     ** being deleted. Do not attempt to delete the row a second time, and
 534     ** do not fire AFTER triggers.  */
 535     sqlite3VdbeAddOp3(v, OP_NotExists, iCur, iLabel, iRowid);
 536
 537     /* Do FK processing. This call checks that any FK constraints that
 538     ** refer to this table (i.e. constraints attached to other tables)
 539     ** are not violated by deleting this row.  */
 540     sqlite3FkCheck(pParse, pTab, iOld, 0);
 541   }
 542
 543   /* Delete the index and table entries. Skip this step if pTab is really
 544   ** a view (in which case the only effect of the DELETE statement is to
 545   ** fire the INSTEAD OF triggers).  */
 546   if( pTab->pSelect==0 ){
 547     sqlite3GenerateRowIndexDelete(pParse, pTab, iCur, 0);
 548     sqlite3VdbeAddOp2(v, OP_Delete, iCur, (count?OPFLAG_NCHANGE:0));
 549     if( count ){
 550       sqlite3VdbeChangeP4(v, -1, pTab->zName, P4_TRANSIENT);
 551     }
 552   }
 553
 554   /* Do any ON CASCADE, SET NULL or SET DEFAULT operations required to
 555   ** handle rows (possibly in other tables) that refer via a foreign key
 556   ** to the row just deleted. */
 557   sqlite3FkActions(pParse, pTab, 0, iOld);
 558
 559   /* Invoke AFTER DELETE trigger programs. */
 560   sqlite3CodeRowTrigger(pParse, pTrigger,
 561       TK_DELETE, 0, TRIGGER_AFTER, pTab, iOld, onconf, iLabel
 562   );
 563
 564   /* Jump here if the row had already been deleted before any BEFORE
 565   ** trigger programs were invoked. Or if a trigger program throws a
 566   ** RAISE(IGNORE) exception.  */
 567   sqlite3VdbeResolveLabel(v, iLabel);
 568 }
 569
 570 /*
 571 ** This routine generates VDBE code that causes the deletion of all
 572 ** index entries associated with a single row of a single table.
 573 **
 574 ** The VDBE must be in a particular state when this routine is called.
 575 ** These are the requirements:
 576 **
 577 **   1.  A read/write cursor pointing to pTab, the table containing the row
 578 **       to be deleted, must be opened as cursor number "iCur".
 579 **
 580 **   2.  Read/write cursors for all indices of pTab must be open as
 581 **       cursor number iCur+i for the i-th index.
 582 **
 583 **   3.  The "iCur" cursor must be pointing to the row that is to be
 584 **       deleted.
 585 */
 586 void sqlite3GenerateRowIndexDelete(
 587   Parse *pParse,     /* Parsing and code generating context */
 588   Table *pTab,       /* Table containing the row to be deleted */
 589   int iCur,          /* Cursor number for the table */
 590   int *aRegIdx       /* Only delete if aRegIdx!=0 && aRegIdx[i]>0 */
 591 ){
 592   int i;
 593   Index *pIdx;
 594   int r1;
 595
 596   for(i=1, pIdx=pTab->pIndex; pIdx; i++, pIdx=pIdx->pNext){
 597     if( aRegIdx!=0 && aRegIdx[i-1]==0 ) continue;
 598     r1 = sqlite3GenerateIndexKey(pParse, pIdx, iCur, 0, 0);
 599     sqlite3VdbeAddOp3(pParse->pVdbe, OP_IdxDelete, iCur+i, r1,pIdx->nColumn+1);
 600   }
 601 }
 602
 603 /*
 604 ** Generate code that will assemble an index key and put it in register
 605 ** regOut.  The key with be for index pIdx which is an index on pTab.
 606 ** iCur is the index of a cursor open on the pTab table and pointing to
 607 ** the entry that needs indexing.
 608 **
 609 ** Return a register number which is the first in a block of
 610 ** registers that holds the elements of the index key.  The
 611 ** block of registers has already been deallocated by the time
 612 ** this routine returns.
 613 */
 614 int sqlite3GenerateIndexKey(
 615   Parse *pParse,     /* Parsing context */
 616   Index *pIdx,       /* The index for which to generate a key */
 617   int iCur,          /* Cursor number for the pIdx->pTable table */
 618   int regOut,        /* Write the new index key to this register */
 619   int doMakeRec      /* Run the OP_MakeRecord instruction if true */
 620 ){
 621   Vdbe *v = pParse->pVdbe;
 622   int j;
 623   Table *pTab = pIdx->pTable;
 624   int regBase;
 625   int nCol;
 626
 627   nCol = pIdx->nColumn;
 628   regBase = sqlite3GetTempRange(pParse, nCol+1);
 629   sqlite3VdbeAddOp2(v, OP_Rowid, iCur, regBase+nCol);
 630   for(j=0; j<nCol; j++){
 631     int idx = pIdx->aiColumn[j];
 632     if( idx==pTab->iPKey ){
 633       sqlite3VdbeAddOp2(v, OP_SCopy, regBase+nCol, regBase+j);
 634     }else{
 635       sqlite3VdbeAddOp3(v, OP_Column, iCur, idx, regBase+j);
 636       sqlite3ColumnDefault(v, pTab, idx, -1);
 637     }
 638   }
 639   if( doMakeRec ){
 640     const char *zAff;
 641     if( pTab->pSelect || (pParse->db->flags & SQLITE_IdxRealAsInt)!=0 ){
 642       zAff = 0;
 643     }else{
 644       zAff = sqlite3IndexAffinityStr(v, pIdx);
 645     }
 646     sqlite3VdbeAddOp3(v, OP_MakeRecord, regBase, nCol+1, regOut);
 647     sqlite3VdbeChangeP4(v, -1, zAff, P4_TRANSIENT);
 648   }
 649   sqlite3ReleaseTempRange(pParse, regBase, nCol+1);
 650   return regBase;
 651 }