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 = sqlite3LocateTableItem(pParse, 0, pItem);
  36   sqlite3DeleteTable(pParse->db, pItem->pTab);
  37   pItem->pTab = pTab;
  38   if( pTab ){
  39     pTab->nTabRef++;
  40   }
  41   if( sqlite3IndexedByLookup(pParse, pItem) ){
  42     pTab = 0;
  43   }
  44   return pTab;
  45 }
  46
  47 /* Return true if table pTab is read-only.
  48 **
  49 ** A table is read-only if any of the following are true:
  50 **
  51 **   1) It is a virtual table and no implementation of the xUpdate method
  52 **      has been provided
  53 **
  54 **   2) It is a system table (i.e. sqlite_master), this call is not
  55 **      part of a nested parse and writable_schema pragma has not
  56 **      been specified
  57 **
  58 **   3) The table is a shadow table, the database connection is in
  59 **      defensive mode, and the current sqlite3_prepare()
  60 **      is for a top-level SQL statement.
  61 */
  62 static int tabIsReadOnly(Parse *pParse, Table *pTab){
  63   sqlite3 *db;
  64   if( IsVirtual(pTab) ){
  65     return sqlite3GetVTable(pParse->db, pTab)->pMod->pModule->xUpdate==0;
  66   }
  67   if( (pTab->tabFlags & (TF_Readonly|TF_Shadow))==0 ) return 0;
  68   db = pParse->db;
  69   if( (pTab->tabFlags & TF_Readonly)!=0 ){
  70     return sqlite3WritableSchema(db)==0 && pParse->nested==0;
  71   }
  72   assert( pTab->tabFlags & TF_Shadow );
  73   return (db->flags & SQLITE_Defensive)!=0
  74 #ifndef SQLITE_OMIT_VIRTUALTABLE
  75           && db->pVtabCtx==0
  76 #endif
  77           && db->nVdbeExec==0;
  78 }
  79
  80 /*
  81 ** Check to make sure the given table is writable.  If it is not
  82 ** writable, generate an error message and return 1.  If it is
  83 ** writable return 0;
  84 */
  85 int sqlite3IsReadOnly(Parse *pParse, Table *pTab, int viewOk){
  86   if( tabIsReadOnly(pParse, pTab) ){
  87     sqlite3ErrorMsg(pParse, "table %s may not be modified", pTab->zName);
  88     return 1;
  89   }
  90 #ifndef SQLITE_OMIT_VIEW
  91   if( !viewOk && pTab->pSelect ){
  92     sqlite3ErrorMsg(pParse,"cannot modify %s because it is a view",pTab->zName);
  93     return 1;
  94   }
  95 #endif
  96   return 0;
  97 }
  98
  99
 100 #if !defined(SQLITE_OMIT_VIEW) && !defined(SQLITE_OMIT_TRIGGER)
 101 /*
 102 ** Evaluate a view and store its result in an ephemeral table.  The
 103 ** pWhere argument is an optional WHERE clause that restricts the
 104 ** set of rows in the view that are to be added to the ephemeral table.
 105 */
 106 void sqlite3MaterializeView(
 107   Parse *pParse,       /* Parsing context */
 108   Table *pView,        /* View definition */
 109   Expr *pWhere,        /* Optional WHERE clause to be added */
 110   ExprList *pOrderBy,  /* Optional ORDER BY clause */
 111   Expr *pLimit,        /* Optional LIMIT clause */
 112   int iCur             /* Cursor number for ephemeral table */
 113 ){
 114   SelectDest dest;
 115   Select *pSel;
 116   SrcList *pFrom;
 117   sqlite3 *db = pParse->db;
 118   int iDb = sqlite3SchemaToIndex(db, pView->pSchema);
 119   pWhere = sqlite3ExprDup(db, pWhere, 0);
 120   pFrom = sqlite3SrcListAppend(pParse, 0, 0, 0);
 121   if( pFrom ){
 122     assert( pFrom->nSrc==1 );
 123     pFrom->a[0].zName = sqlite3DbStrDup(db, pView->zName);
 124     pFrom->a[0].zDatabase = sqlite3DbStrDup(db, db->aDb[iDb].zDbSName);
 125     assert( pFrom->a[0].pOn==0 );
 126     assert( pFrom->a[0].pUsing==0 );
 127   }
 128   pSel = sqlite3SelectNew(pParse, 0, pFrom, pWhere, 0, 0, pOrderBy,
 129                           SF_IncludeHidden, pLimit);
 130   sqlite3SelectDestInit(&dest, SRT_EphemTab, iCur);
 131   sqlite3Select(pParse, pSel, &dest);
 132   sqlite3SelectDelete(db, pSel);
 133 }
 134 #endif /* !defined(SQLITE_OMIT_VIEW) && !defined(SQLITE_OMIT_TRIGGER) */
 135
 136 #if defined(SQLITE_ENABLE_UPDATE_DELETE_LIMIT) && !defined(SQLITE_OMIT_SUBQUERY)
 137 /*
 138 ** Generate an expression tree to implement the WHERE, ORDER BY,
 139 ** and LIMIT/OFFSET portion of DELETE and UPDATE statements.
 140 **
 141 **     DELETE FROM table_wxyz WHERE a<5 ORDER BY a LIMIT 1;
 142 **                            \__________________________/
 143 **                               pLimitWhere (pInClause)
 144 */
 145 Expr *sqlite3LimitWhere(
 146   Parse *pParse,               /* The parser context */
 147   SrcList *pSrc,               /* the FROM clause -- which tables to scan */
 148   Expr *pWhere,                /* The WHERE clause.  May be null */
 149   ExprList *pOrderBy,          /* The ORDER BY clause.  May be null */
 150   Expr *pLimit,                /* The LIMIT clause.  May be null */
 151   char *zStmtType              /* Either DELETE or UPDATE.  For err msgs. */
 152 ){
 153   sqlite3 *db = pParse->db;
 154   Expr *pLhs = NULL;           /* LHS of IN(SELECT...) operator */
 155   Expr *pInClause = NULL;      /* WHERE rowid IN ( select ) */
 156   ExprList *pEList = NULL;     /* Expression list contaning only pSelectRowid */
 157   SrcList *pSelectSrc = NULL;  /* SELECT rowid FROM x ... (dup of pSrc) */
 158   Select *pSelect = NULL;      /* Complete SELECT tree */
 159   Table *pTab;
 160
 161   /* Check that there isn't an ORDER BY without a LIMIT clause.
 162   */
 163   if( pOrderBy && pLimit==0 ) {
 164     sqlite3ErrorMsg(pParse, "ORDER BY without LIMIT on %s", zStmtType);
 165     sqlite3ExprDelete(pParse->db, pWhere);
 166     sqlite3ExprListDelete(pParse->db, pOrderBy);
 167     return 0;
 168   }
 169
 170   /* We only need to generate a select expression if there
 171   ** is a limit/offset term to enforce.
 172   */
 173   if( pLimit == 0 ) {
 174     return pWhere;
 175   }
 176
 177   /* Generate a select expression tree to enforce the limit/offset
 178   ** term for the DELETE or UPDATE statement.  For example:
 179   **   DELETE FROM table_a WHERE col1=1 ORDER BY col2 LIMIT 1 OFFSET 1
 180   ** becomes:
 181   **   DELETE FROM table_a WHERE rowid IN (
 182   **     SELECT rowid FROM table_a WHERE col1=1 ORDER BY col2 LIMIT 1 OFFSET 1
 183   **   );
 184   */
 185
 186   pTab = pSrc->a[0].pTab;
 187   if( HasRowid(pTab) ){
 188     pLhs = sqlite3PExpr(pParse, TK_ROW, 0, 0);
 189     pEList = sqlite3ExprListAppend(
 190         pParse, 0, sqlite3PExpr(pParse, TK_ROW, 0, 0)
 191     );
 192   }else{
 193     Index *pPk = sqlite3PrimaryKeyIndex(pTab);
 194     if( pPk->nKeyCol==1 ){
 195       const char *zName = pTab->aCol[pPk->aiColumn[0]].zName;
 196       pLhs = sqlite3Expr(db, TK_ID, zName);
 197       pEList = sqlite3ExprListAppend(pParse, 0, sqlite3Expr(db, TK_ID, zName));
 198     }else{
 199       int i;
 200       for(i=0; i<pPk->nKeyCol; i++){
 201         Expr *p = sqlite3Expr(db, TK_ID, pTab->aCol[pPk->aiColumn[i]].zName);
 202         pEList = sqlite3ExprListAppend(pParse, pEList, p);
 203       }
 204       pLhs = sqlite3PExpr(pParse, TK_VECTOR, 0, 0);
 205       if( pLhs ){
 206         pLhs->x.pList = sqlite3ExprListDup(db, pEList, 0);
 207       }
 208     }
 209   }
 210
 211   /* duplicate the FROM clause as it is needed by both the DELETE/UPDATE tree
 212   ** and the SELECT subtree. */
 213   pSrc->a[0].pTab = 0;
 214   pSelectSrc = sqlite3SrcListDup(pParse->db, pSrc, 0);
 215   pSrc->a[0].pTab = pTab;
 216   pSrc->a[0].pIBIndex = 0;
 217
 218   /* generate the SELECT expression tree. */
 219   pSelect = sqlite3SelectNew(pParse, pEList, pSelectSrc, pWhere, 0 ,0,
 220       pOrderBy,0,pLimit
 221   );
 222
 223   /* now generate the new WHERE rowid IN clause for the DELETE/UDPATE */
 224   pInClause = sqlite3PExpr(pParse, TK_IN, pLhs, 0);
 225   sqlite3PExprAddSelect(pParse, pInClause, pSelect);
 226   return pInClause;
 227 }
 228 #endif /* defined(SQLITE_ENABLE_UPDATE_DELETE_LIMIT) */
 229        /*      && !defined(SQLITE_OMIT_SUBQUERY) */
 230
 231 /*
 232 ** Generate code for a DELETE FROM statement.
 233 **
 234 **     DELETE FROM table_wxyz WHERE a<5 AND b NOT NULL;
 235 **                 \________/       \________________/
 236 **                  pTabList              pWhere
 237 */
 238 void sqlite3DeleteFrom(
 239   Parse *pParse,         /* The parser context */
 240   SrcList *pTabList,     /* The table from which we should delete things */
 241   Expr *pWhere,          /* The WHERE clause.  May be null */
 242   ExprList *pOrderBy,    /* ORDER BY clause. May be null */
 243   Expr *pLimit           /* LIMIT clause. May be null */
 244 ){
 245   Vdbe *v;               /* The virtual database engine */
 246   Table *pTab;           /* The table from which records will be deleted */
 247   int i;                 /* Loop counter */
 248   WhereInfo *pWInfo;     /* Information about the WHERE clause */
 249   Index *pIdx;           /* For looping over indices of the table */
 250   int iTabCur;           /* Cursor number for the table */
 251   int iDataCur = 0;      /* VDBE cursor for the canonical data source */
 252   int iIdxCur = 0;       /* Cursor number of the first index */
 253   int nIdx;              /* Number of indices */
 254   sqlite3 *db;           /* Main database structure */
 255   AuthContext sContext;  /* Authorization context */
 256   NameContext sNC;       /* Name context to resolve expressions in */
 257   int iDb;               /* Database number */
 258   int memCnt = 0;        /* Memory cell used for change counting */
 259   int rcauth;            /* Value returned by authorization callback */
 260   int eOnePass;          /* ONEPASS_OFF or _SINGLE or _MULTI */
 261   int aiCurOnePass[2];   /* The write cursors opened by WHERE_ONEPASS */
 262   u8 *aToOpen = 0;       /* Open cursor iTabCur+j if aToOpen[j] is true */
 263   Index *pPk;            /* The PRIMARY KEY index on the table */
 264   int iPk = 0;           /* First of nPk registers holding PRIMARY KEY value */
 265   i16 nPk = 1;           /* Number of columns in the PRIMARY KEY */
 266   int iKey;              /* Memory cell holding key of row to be deleted */
 267   i16 nKey;              /* Number of memory cells in the row key */
 268   int iEphCur = 0;       /* Ephemeral table holding all primary key values */
 269   int iRowSet = 0;       /* Register for rowset of rows to delete */
 270   int addrBypass = 0;    /* Address of jump over the delete logic */
 271   int addrLoop = 0;      /* Top of the delete loop */
 272   int addrEphOpen = 0;   /* Instruction to open the Ephemeral table */
 273   int bComplex;          /* True if there are triggers or FKs or
 274                          ** subqueries in the WHERE clause */
 275
 276 #ifndef SQLITE_OMIT_TRIGGER
 277   int isView;                  /* True if attempting to delete from a view */
 278   Trigger *pTrigger;           /* List of table triggers, if required */
 279 #endif
 280
 281   memset(&sContext, 0, sizeof(sContext));
 282   db = pParse->db;
 283   if( pParse->nErr || db->mallocFailed ){
 284     goto delete_from_cleanup;
 285   }
 286   assert( pTabList->nSrc==1 );
 287
 288
 289   /* Locate the table which we want to delete.  This table has to be
 290   ** put in an SrcList structure because some of the subroutines we
 291   ** will be calling are designed to work with multiple tables and expect
 292   ** an SrcList* parameter instead of just a Table* parameter.
 293   */
 294   pTab = sqlite3SrcListLookup(pParse, pTabList);
 295   if( pTab==0 )  goto delete_from_cleanup;
 296
 297   /* Figure out if we have any triggers and if the table being
 298   ** deleted from is a view
 299   */
 300 #ifndef SQLITE_OMIT_TRIGGER
 301   pTrigger = sqlite3TriggersExist(pParse, pTab, TK_DELETE, 0, 0);
 302   isView = pTab->pSelect!=0;
 303 #else
 304 # define pTrigger 0
 305 # define isView 0
 306 #endif
 307   bComplex = pTrigger || sqlite3FkRequired(pParse, pTab, 0, 0);
 308 #ifdef SQLITE_OMIT_VIEW
 309 # undef isView
 310 # define isView 0
 311 #endif
 312
 313 #ifdef SQLITE_ENABLE_UPDATE_DELETE_LIMIT
 314   if( !isView ){
 315     pWhere = sqlite3LimitWhere(
 316         pParse, pTabList, pWhere, pOrderBy, pLimit, "DELETE"
 317     );
 318     pOrderBy = 0;
 319     pLimit = 0;
 320   }
 321 #endif
 322
 323   /* If pTab is really a view, make sure it has been initialized.
 324   */
 325   if( sqlite3ViewGetColumnNames(pParse, pTab) ){
 326     goto delete_from_cleanup;
 327   }
 328
 329   if( sqlite3IsReadOnly(pParse, pTab, (pTrigger?1:0)) ){
 330     goto delete_from_cleanup;
 331   }
 332   iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
 333   assert( iDb<db->nDb );
 334   rcauth = sqlite3AuthCheck(pParse, SQLITE_DELETE, pTab->zName, 0,
 335                             db->aDb[iDb].zDbSName);
 336   assert( rcauth==SQLITE_OK || rcauth==SQLITE_DENY || rcauth==SQLITE_IGNORE );
 337   if( rcauth==SQLITE_DENY ){
 338     goto delete_from_cleanup;
 339   }
 340   assert(!isView || pTrigger);
 341
 342   /* Assign cursor numbers to the table and all its indices.
 343   */
 344   assert( pTabList->nSrc==1 );
 345   iTabCur = pTabList->a[0].iCursor = pParse->nTab++;
 346   for(nIdx=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, nIdx++){
 347     pParse->nTab++;
 348   }
 349
 350   /* Start the view context
 351   */
 352   if( isView ){
 353     sqlite3AuthContextPush(pParse, &sContext, pTab->zName);
 354   }
 355
 356   /* Begin generating code.
 357   */
 358   v = sqlite3GetVdbe(pParse);
 359   if( v==0 ){
 360     goto delete_from_cleanup;
 361   }
 362   if( pParse->nested==0 ) sqlite3VdbeCountChanges(v);
 363   sqlite3BeginWriteOperation(pParse, bComplex, iDb);
 364
 365   /* If we are trying to delete from a view, realize that view into
 366   ** an ephemeral table.
 367   */
 368 #if !defined(SQLITE_OMIT_VIEW) && !defined(SQLITE_OMIT_TRIGGER)
 369   if( isView ){
 370     sqlite3MaterializeView(pParse, pTab,
 371         pWhere, pOrderBy, pLimit, iTabCur
 372     );
 373     iDataCur = iIdxCur = iTabCur;
 374     pOrderBy = 0;
 375     pLimit = 0;
 376   }
 377 #endif
 378
 379   /* Resolve the column names in the WHERE clause.
 380   */
 381   memset(&sNC, 0, sizeof(sNC));
 382   sNC.pParse = pParse;
 383   sNC.pSrcList = pTabList;
 384   if( sqlite3ResolveExprNames(&sNC, pWhere) ){
 385     goto delete_from_cleanup;
 386   }
 387
 388   /* Initialize the counter of the number of rows deleted, if
 389   ** we are counting rows.
 390   */
 391   if( (db->flags & SQLITE_CountRows)!=0
 392    && !pParse->nested
 393    && !pParse->pTriggerTab
 394   ){
 395     memCnt = ++pParse->nMem;
 396     sqlite3VdbeAddOp2(v, OP_Integer, 0, memCnt);
 397   }
 398
 399 #ifndef SQLITE_OMIT_TRUNCATE_OPTIMIZATION
 400   /* Special case: A DELETE without a WHERE clause deletes everything.
 401   ** It is easier just to erase the whole table. Prior to version 3.6.5,
 402   ** this optimization caused the row change count (the value returned by
 403   ** API function sqlite3_count_changes) to be set incorrectly.
 404   **
 405   ** The "rcauth==SQLITE_OK" terms is the
 406   ** IMPLEMENTATION-OF: R-17228-37124 If the action code is SQLITE_DELETE and
 407   ** the callback returns SQLITE_IGNORE then the DELETE operation proceeds but
 408   ** the truncate optimization is disabled and all rows are deleted
 409   ** individually.
 410   */
 411   if( rcauth==SQLITE_OK
 412    && pWhere==0
 413    && !bComplex
 414    && !IsVirtual(pTab)
 415 #ifdef SQLITE_ENABLE_PREUPDATE_HOOK
 416    && db->xPreUpdateCallback==0
 417 #endif
 418   ){
 419     assert( !isView );
 420     sqlite3TableLock(pParse, iDb, pTab->tnum, 1, pTab->zName);
 421     if( HasRowid(pTab) ){
 422       sqlite3VdbeAddOp4(v, OP_Clear, pTab->tnum, iDb, memCnt ? memCnt : -1,
 423                         pTab->zName, P4_STATIC);
 424     }
 425     for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
 426       assert( pIdx->pSchema==pTab->pSchema );
 427       sqlite3VdbeAddOp2(v, OP_Clear, pIdx->tnum, iDb);
 428     }
 429   }else
 430 #endif /* SQLITE_OMIT_TRUNCATE_OPTIMIZATION */
 431   {
 432     u16 wcf = WHERE_ONEPASS_DESIRED|WHERE_DUPLICATES_OK|WHERE_SEEK_TABLE;
 433     if( sNC.ncFlags & NC_VarSelect ) bComplex = 1;
 434     wcf |= (bComplex ? 0 : WHERE_ONEPASS_MULTIROW);
 435     if( HasRowid(pTab) ){
 436       /* For a rowid table, initialize the RowSet to an empty set */
 437       pPk = 0;
 438       nPk = 1;
 439       iRowSet = ++pParse->nMem;
 440       sqlite3VdbeAddOp2(v, OP_Null, 0, iRowSet);
 441     }else{
 442       /* For a WITHOUT ROWID table, create an ephemeral table used to
 443       ** hold all primary keys for rows to be deleted. */
 444       pPk = sqlite3PrimaryKeyIndex(pTab);
 445       assert( pPk!=0 );
 446       nPk = pPk->nKeyCol;
 447       iPk = pParse->nMem+1;
 448       pParse->nMem += nPk;
 449       iEphCur = pParse->nTab++;
 450       addrEphOpen = sqlite3VdbeAddOp2(v, OP_OpenEphemeral, iEphCur, nPk);
 451       sqlite3VdbeSetP4KeyInfo(pParse, pPk);
 452     }
 453
 454     /* Construct a query to find the rowid or primary key for every row
 455     ** to be deleted, based on the WHERE clause. Set variable eOnePass
 456     ** to indicate the strategy used to implement this delete:
 457     **
 458     **  ONEPASS_OFF:    Two-pass approach - use a FIFO for rowids/PK values.
 459     **  ONEPASS_SINGLE: One-pass approach - at most one row deleted.
 460     **  ONEPASS_MULTI:  One-pass approach - any number of rows may be deleted.
 461     */
 462     pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, 0, 0, wcf, iTabCur+1);
 463     if( pWInfo==0 ) goto delete_from_cleanup;
 464     eOnePass = sqlite3WhereOkOnePass(pWInfo, aiCurOnePass);
 465     assert( IsVirtual(pTab)==0 || eOnePass!=ONEPASS_MULTI );
 466     assert( IsVirtual(pTab) || bComplex || eOnePass!=ONEPASS_OFF );
 467     if( eOnePass!=ONEPASS_SINGLE ) sqlite3MultiWrite(pParse);
 468
 469     /* Keep track of the number of rows to be deleted */
 470     if( memCnt ){
 471       sqlite3VdbeAddOp2(v, OP_AddImm, memCnt, 1);
 472     }
 473
 474     /* Extract the rowid or primary key for the current row */
 475     if( pPk ){
 476       for(i=0; i<nPk; i++){
 477         assert( pPk->aiColumn[i]>=0 );
 478         sqlite3ExprCodeGetColumnOfTable(v, pTab, iTabCur,
 479                                         pPk->aiColumn[i], iPk+i);
 480       }
 481       iKey = iPk;
 482     }else{
 483       iKey = ++pParse->nMem;
 484       sqlite3ExprCodeGetColumnOfTable(v, pTab, iTabCur, -1, iKey);
 485     }
 486
 487     if( eOnePass!=ONEPASS_OFF ){
 488       /* For ONEPASS, no need to store the rowid/primary-key. There is only
 489       ** one, so just keep it in its register(s) and fall through to the
 490       ** delete code.  */
 491       nKey = nPk; /* OP_Found will use an unpacked key */
 492       aToOpen = sqlite3DbMallocRawNN(db, nIdx+2);
 493       if( aToOpen==0 ){
 494         sqlite3WhereEnd(pWInfo);
 495         goto delete_from_cleanup;
 496       }
 497       memset(aToOpen, 1, nIdx+1);
 498       aToOpen[nIdx+1] = 0;
 499       if( aiCurOnePass[0]>=0 ) aToOpen[aiCurOnePass[0]-iTabCur] = 0;
 500       if( aiCurOnePass[1]>=0 ) aToOpen[aiCurOnePass[1]-iTabCur] = 0;
 501       if( addrEphOpen ) sqlite3VdbeChangeToNoop(v, addrEphOpen);
 502     }else{
 503       if( pPk ){
 504         /* Add the PK key for this row to the temporary table */
 505         iKey = ++pParse->nMem;
 506         nKey = 0;   /* Zero tells OP_Found to use a composite key */
 507         sqlite3VdbeAddOp4(v, OP_MakeRecord, iPk, nPk, iKey,
 508             sqlite3IndexAffinityStr(pParse->db, pPk), nPk);
 509         sqlite3VdbeAddOp4Int(v, OP_IdxInsert, iEphCur, iKey, iPk, nPk);
 510       }else{
 511         /* Add the rowid of the row to be deleted to the RowSet */
 512         nKey = 1;  /* OP_DeferredSeek always uses a single rowid */
 513         sqlite3VdbeAddOp2(v, OP_RowSetAdd, iRowSet, iKey);
 514       }
 515     }
 516
 517     /* If this DELETE cannot use the ONEPASS strategy, this is the
 518     ** end of the WHERE loop */
 519     if( eOnePass!=ONEPASS_OFF ){
 520       addrBypass = sqlite3VdbeMakeLabel(pParse);
 521     }else{
 522       sqlite3WhereEnd(pWInfo);
 523     }
 524
 525     /* Unless this is a view, open cursors for the table we are
 526     ** deleting from and all its indices. If this is a view, then the
 527     ** only effect this statement has is to fire the INSTEAD OF
 528     ** triggers.
 529     */
 530     if( !isView ){
 531       int iAddrOnce = 0;
 532       if( eOnePass==ONEPASS_MULTI ){
 533         iAddrOnce = sqlite3VdbeAddOp0(v, OP_Once); VdbeCoverage(v);
 534       }
 535       testcase( IsVirtual(pTab) );
 536       sqlite3OpenTableAndIndices(pParse, pTab, OP_OpenWrite, OPFLAG_FORDELETE,
 537                                  iTabCur, aToOpen, &iDataCur, &iIdxCur);
 538       assert( pPk || IsVirtual(pTab) || iDataCur==iTabCur );
 539       assert( pPk || IsVirtual(pTab) || iIdxCur==iDataCur+1 );
 540       if( eOnePass==ONEPASS_MULTI ) sqlite3VdbeJumpHere(v, iAddrOnce);
 541     }
 542
 543     /* Set up a loop over the rowids/primary-keys that were found in the
 544     ** where-clause loop above.
 545     */
 546     if( eOnePass!=ONEPASS_OFF ){
 547       assert( nKey==nPk );  /* OP_Found will use an unpacked key */
 548       if( !IsVirtual(pTab) && aToOpen[iDataCur-iTabCur] ){
 549         assert( pPk!=0 || pTab->pSelect!=0 );
 550         sqlite3VdbeAddOp4Int(v, OP_NotFound, iDataCur, addrBypass, iKey, nKey);
 551         VdbeCoverage(v);
 552       }
 553     }else if( pPk ){
 554       addrLoop = sqlite3VdbeAddOp1(v, OP_Rewind, iEphCur); VdbeCoverage(v);
 555       if( IsVirtual(pTab) ){
 556         sqlite3VdbeAddOp3(v, OP_Column, iEphCur, 0, iKey);
 557       }else{
 558         sqlite3VdbeAddOp2(v, OP_RowData, iEphCur, iKey);
 559       }
 560       assert( nKey==0 );  /* OP_Found will use a composite key */
 561     }else{
 562       addrLoop = sqlite3VdbeAddOp3(v, OP_RowSetRead, iRowSet, 0, iKey);
 563       VdbeCoverage(v);
 564       assert( nKey==1 );
 565     }
 566
 567     /* Delete the row */
 568 #ifndef SQLITE_OMIT_VIRTUALTABLE
 569     if( IsVirtual(pTab) ){
 570       const char *pVTab = (const char *)sqlite3GetVTable(db, pTab);
 571       sqlite3VtabMakeWritable(pParse, pTab);
 572       assert( eOnePass==ONEPASS_OFF || eOnePass==ONEPASS_SINGLE );
 573       sqlite3MayAbort(pParse);
 574       if( eOnePass==ONEPASS_SINGLE ){
 575         sqlite3VdbeAddOp1(v, OP_Close, iTabCur);
 576         if( sqlite3IsToplevel(pParse) ){
 577           pParse->isMultiWrite = 0;
 578         }
 579       }
 580       sqlite3VdbeAddOp4(v, OP_VUpdate, 0, 1, iKey, pVTab, P4_VTAB);
 581       sqlite3VdbeChangeP5(v, OE_Abort);
 582     }else
 583 #endif
 584     {
 585       int count = (pParse->nested==0);    /* True to count changes */
 586       sqlite3GenerateRowDelete(pParse, pTab, pTrigger, iDataCur, iIdxCur,
 587           iKey, nKey, count, OE_Default, eOnePass, aiCurOnePass[1]);
 588     }
 589
 590     /* End of the loop over all rowids/primary-keys. */
 591     if( eOnePass!=ONEPASS_OFF ){
 592       sqlite3VdbeResolveLabel(v, addrBypass);
 593       sqlite3WhereEnd(pWInfo);
 594     }else if( pPk ){
 595       sqlite3VdbeAddOp2(v, OP_Next, iEphCur, addrLoop+1); VdbeCoverage(v);
 596       sqlite3VdbeJumpHere(v, addrLoop);
 597     }else{
 598       sqlite3VdbeGoto(v, addrLoop);
 599       sqlite3VdbeJumpHere(v, addrLoop);
 600     }
 601   } /* End non-truncate path */
 602
 603   /* Update the sqlite_sequence table by storing the content of the
 604   ** maximum rowid counter values recorded while inserting into
 605   ** autoincrement tables.
 606   */
 607   if( pParse->nested==0 && pParse->pTriggerTab==0 ){
 608     sqlite3AutoincrementEnd(pParse);
 609   }
 610
 611   /* Return the number of rows that were deleted. If this routine is
 612   ** generating code because of a call to sqlite3NestedParse(), do not
 613   ** invoke the callback function.
 614   */
 615   if( memCnt ){
 616     sqlite3VdbeAddOp2(v, OP_ResultRow, memCnt, 1);
 617     sqlite3VdbeSetNumCols(v, 1);
 618     sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "rows deleted", SQLITE_STATIC);
 619   }
 620
 621 delete_from_cleanup:
 622   sqlite3AuthContextPop(&sContext);
 623   sqlite3SrcListDelete(db, pTabList);
 624   sqlite3ExprDelete(db, pWhere);
 625 #if defined(SQLITE_ENABLE_UPDATE_DELETE_LIMIT)
 626   sqlite3ExprListDelete(db, pOrderBy);
 627   sqlite3ExprDelete(db, pLimit);
 628 #endif
 629   sqlite3DbFree(db, aToOpen);
 630   return;
 631 }
 632 /* Make sure "isView" and other macros defined above are undefined. Otherwise
 633 ** they may interfere with compilation of other functions in this file
 634 ** (or in another file, if this file becomes part of the amalgamation).  */
 635 #ifdef isView
 636  #undef isView
 637 #endif
 638 #ifdef pTrigger
 639  #undef pTrigger
 640 #endif
 641
 642 /*
 643 ** This routine generates VDBE code that causes a single row of a
 644 ** single table to be deleted.  Both the original table entry and
 645 ** all indices are removed.
 646 **
 647 ** Preconditions:
 648 **
 649 **   1.  iDataCur is an open cursor on the btree that is the canonical data
 650 **       store for the table.  (This will be either the table itself,
 651 **       in the case of a rowid table, or the PRIMARY KEY index in the case
 652 **       of a WITHOUT ROWID table.)
 653 **
 654 **   2.  Read/write cursors for all indices of pTab must be open as
 655 **       cursor number iIdxCur+i for the i-th index.
 656 **
 657 **   3.  The primary key for the row to be deleted must be stored in a
 658 **       sequence of nPk memory cells starting at iPk.  If nPk==0 that means
 659 **       that a search record formed from OP_MakeRecord is contained in the
 660 **       single memory location iPk.
 661 **
 662 ** eMode:
 663 **   Parameter eMode may be passed either ONEPASS_OFF (0), ONEPASS_SINGLE, or
 664 **   ONEPASS_MULTI.  If eMode is not ONEPASS_OFF, then the cursor
 665 **   iDataCur already points to the row to delete. If eMode is ONEPASS_OFF
 666 **   then this function must seek iDataCur to the entry identified by iPk
 667 **   and nPk before reading from it.
 668 **
 669 **   If eMode is ONEPASS_MULTI, then this call is being made as part
 670 **   of a ONEPASS delete that affects multiple rows. In this case, if
 671 **   iIdxNoSeek is a valid cursor number (>=0) and is not the same as
 672 **   iDataCur, then its position should be preserved following the delete
 673 **   operation. Or, if iIdxNoSeek is not a valid cursor number, the
 674 **   position of iDataCur should be preserved instead.
 675 **
 676 ** iIdxNoSeek:
 677 **   If iIdxNoSeek is a valid cursor number (>=0) not equal to iDataCur,
 678 **   then it identifies an index cursor (from within array of cursors
 679 **   starting at iIdxCur) that already points to the index entry to be deleted.
 680 **   Except, this optimization is disabled if there are BEFORE triggers since
 681 **   the trigger body might have moved the cursor.
 682 */
 683 void sqlite3GenerateRowDelete(
 684   Parse *pParse,     /* Parsing context */
 685   Table *pTab,       /* Table containing the row to be deleted */
 686   Trigger *pTrigger, /* List of triggers to (potentially) fire */
 687   int iDataCur,      /* Cursor from which column data is extracted */
 688   int iIdxCur,       /* First index cursor */
 689   int iPk,           /* First memory cell containing the PRIMARY KEY */
 690   i16 nPk,           /* Number of PRIMARY KEY memory cells */
 691   u8 count,          /* If non-zero, increment the row change counter */
 692   u8 onconf,         /* Default ON CONFLICT policy for triggers */
 693   u8 eMode,          /* ONEPASS_OFF, _SINGLE, or _MULTI.  See above */
 694   int iIdxNoSeek     /* Cursor number of cursor that does not need seeking */
 695 ){
 696   Vdbe *v = pParse->pVdbe;        /* Vdbe */
 697   int iOld = 0;                   /* First register in OLD.* array */
 698   int iLabel;                     /* Label resolved to end of generated code */
 699   u8 opSeek;                      /* Seek opcode */
 700
 701   /* Vdbe is guaranteed to have been allocated by this stage. */
 702   assert( v );
 703   VdbeModuleComment((v, "BEGIN: GenRowDel(%d,%d,%d,%d)",
 704                          iDataCur, iIdxCur, iPk, (int)nPk));
 705
 706   /* Seek cursor iCur to the row to delete. If this row no longer exists
 707   ** (this can happen if a trigger program has already deleted it), do
 708   ** not attempt to delete it or fire any DELETE triggers.  */
 709   iLabel = sqlite3VdbeMakeLabel(pParse);
 710   opSeek = HasRowid(pTab) ? OP_NotExists : OP_NotFound;
 711   if( eMode==ONEPASS_OFF ){
 712     sqlite3VdbeAddOp4Int(v, opSeek, iDataCur, iLabel, iPk, nPk);
 713     VdbeCoverageIf(v, opSeek==OP_NotExists);
 714     VdbeCoverageIf(v, opSeek==OP_NotFound);
 715   }
 716
 717   /* If there are any triggers to fire, allocate a range of registers to
 718   ** use for the old.* references in the triggers.  */
 719   if( sqlite3FkRequired(pParse, pTab, 0, 0) || pTrigger ){
 720     u32 mask;                     /* Mask of OLD.* columns in use */
 721     int iCol;                     /* Iterator used while populating OLD.* */
 722     int addrStart;                /* Start of BEFORE trigger programs */
 723
 724     /* TODO: Could use temporary registers here. Also could attempt to
 725     ** avoid copying the contents of the rowid register.  */
 726     mask = sqlite3TriggerColmask(
 727         pParse, pTrigger, 0, 0, TRIGGER_BEFORE|TRIGGER_AFTER, pTab, onconf
 728     );
 729     mask |= sqlite3FkOldmask(pParse, pTab);
 730     iOld = pParse->nMem+1;
 731     pParse->nMem += (1 + pTab->nCol);
 732
 733     /* Populate the OLD.* pseudo-table register array. These values will be
 734     ** used by any BEFORE and AFTER triggers that exist.  */
 735     sqlite3VdbeAddOp2(v, OP_Copy, iPk, iOld);
 736     for(iCol=0; iCol<pTab->nCol; iCol++){
 737       testcase( mask!=0xffffffff && iCol==31 );
 738       testcase( mask!=0xffffffff && iCol==32 );
 739       if( mask==0xffffffff || (iCol<=31 && (mask & MASKBIT32(iCol))!=0) ){
 740         sqlite3ExprCodeGetColumnOfTable(v, pTab, iDataCur, iCol, iOld+iCol+1);
 741       }
 742     }
 743
 744     /* Invoke BEFORE DELETE trigger programs. */
 745     addrStart = sqlite3VdbeCurrentAddr(v);
 746     sqlite3CodeRowTrigger(pParse, pTrigger,
 747         TK_DELETE, 0, TRIGGER_BEFORE, pTab, iOld, onconf, iLabel
 748     );
 749
 750     /* If any BEFORE triggers were coded, then seek the cursor to the
 751     ** row to be deleted again. It may be that the BEFORE triggers moved
 752     ** the cursor or already deleted the row that the cursor was
 753     ** pointing to.
 754     **
 755     ** Also disable the iIdxNoSeek optimization since the BEFORE trigger
 756     ** may have moved that cursor.
 757     */
 758     if( addrStart<sqlite3VdbeCurrentAddr(v) ){
 759       sqlite3VdbeAddOp4Int(v, opSeek, iDataCur, iLabel, iPk, nPk);
 760       VdbeCoverageIf(v, opSeek==OP_NotExists);
 761       VdbeCoverageIf(v, opSeek==OP_NotFound);
 762       testcase( iIdxNoSeek>=0 );
 763       iIdxNoSeek = -1;
 764     }
 765
 766     /* Do FK processing. This call checks that any FK constraints that
 767     ** refer to this table (i.e. constraints attached to other tables)
 768     ** are not violated by deleting this row.  */
 769     sqlite3FkCheck(pParse, pTab, iOld, 0, 0, 0);
 770   }
 771
 772   /* Delete the index and table entries. Skip this step if pTab is really
 773   ** a view (in which case the only effect of the DELETE statement is to
 774   ** fire the INSTEAD OF triggers).
 775   **
 776   ** If variable 'count' is non-zero, then this OP_Delete instruction should
 777   ** invoke the update-hook. The pre-update-hook, on the other hand should
 778   ** be invoked unless table pTab is a system table. The difference is that
 779   ** the update-hook is not invoked for rows removed by REPLACE, but the
 780   ** pre-update-hook is.
 781   */
 782   if( pTab->pSelect==0 ){
 783     u8 p5 = 0;
 784     sqlite3GenerateRowIndexDelete(pParse, pTab, iDataCur, iIdxCur,0,iIdxNoSeek);
 785     sqlite3VdbeAddOp2(v, OP_Delete, iDataCur, (count?OPFLAG_NCHANGE:0));
 786     if( pParse->nested==0 || 0==sqlite3_stricmp(pTab->zName, "sqlite_stat1") ){
 787       sqlite3VdbeAppendP4(v, (char*)pTab, P4_TABLE);
 788     }
 789     if( eMode!=ONEPASS_OFF ){
 790       sqlite3VdbeChangeP5(v, OPFLAG_AUXDELETE);
 791     }
 792     if( iIdxNoSeek>=0 && iIdxNoSeek!=iDataCur ){
 793       sqlite3VdbeAddOp1(v, OP_Delete, iIdxNoSeek);
 794     }
 795     if( eMode==ONEPASS_MULTI ) p5 |= OPFLAG_SAVEPOSITION;
 796     sqlite3VdbeChangeP5(v, p5);
 797   }
 798
 799   /* Do any ON CASCADE, SET NULL or SET DEFAULT operations required to
 800   ** handle rows (possibly in other tables) that refer via a foreign key
 801   ** to the row just deleted. */
 802   sqlite3FkActions(pParse, pTab, 0, iOld, 0, 0);
 803
 804   /* Invoke AFTER DELETE trigger programs. */
 805   sqlite3CodeRowTrigger(pParse, pTrigger,
 806       TK_DELETE, 0, TRIGGER_AFTER, pTab, iOld, onconf, iLabel
 807   );
 808
 809   /* Jump here if the row had already been deleted before any BEFORE
 810   ** trigger programs were invoked. Or if a trigger program throws a
 811   ** RAISE(IGNORE) exception.  */
 812   sqlite3VdbeResolveLabel(v, iLabel);
 813   VdbeModuleComment((v, "END: GenRowDel()"));
 814 }
 815
 816 /*
 817 ** This routine generates VDBE code that causes the deletion of all
 818 ** index entries associated with a single row of a single table, pTab
 819 **
 820 ** Preconditions:
 821 **
 822 **   1.  A read/write cursor "iDataCur" must be open on the canonical storage
 823 **       btree for the table pTab.  (This will be either the table itself
 824 **       for rowid tables or to the primary key index for WITHOUT ROWID
 825 **       tables.)
 826 **
 827 **   2.  Read/write cursors for all indices of pTab must be open as
 828 **       cursor number iIdxCur+i for the i-th index.  (The pTab->pIndex
 829 **       index is the 0-th index.)
 830 **
 831 **   3.  The "iDataCur" cursor must be already be positioned on the row
 832 **       that is to be deleted.
 833 */
 834 void sqlite3GenerateRowIndexDelete(
 835   Parse *pParse,     /* Parsing and code generating context */
 836   Table *pTab,       /* Table containing the row to be deleted */
 837   int iDataCur,      /* Cursor of table holding data. */
 838   int iIdxCur,       /* First index cursor */
 839   int *aRegIdx,      /* Only delete if aRegIdx!=0 && aRegIdx[i]>0 */
 840   int iIdxNoSeek     /* Do not delete from this cursor */
 841 ){
 842   int i;             /* Index loop counter */
 843   int r1 = -1;       /* Register holding an index key */
 844   int iPartIdxLabel; /* Jump destination for skipping partial index entries */
 845   Index *pIdx;       /* Current index */
 846   Index *pPrior = 0; /* Prior index */
 847   Vdbe *v;           /* The prepared statement under construction */
 848   Index *pPk;        /* PRIMARY KEY index, or NULL for rowid tables */
 849
 850   v = pParse->pVdbe;
 851   pPk = HasRowid(pTab) ? 0 : sqlite3PrimaryKeyIndex(pTab);
 852   for(i=0, pIdx=pTab->pIndex; pIdx; i++, pIdx=pIdx->pNext){
 853     assert( iIdxCur+i!=iDataCur || pPk==pIdx );
 854     if( aRegIdx!=0 && aRegIdx[i]==0 ) continue;
 855     if( pIdx==pPk ) continue;
 856     if( iIdxCur+i==iIdxNoSeek ) continue;
 857     VdbeModuleComment((v, "GenRowIdxDel for %s", pIdx->zName));
 858     r1 = sqlite3GenerateIndexKey(pParse, pIdx, iDataCur, 0, 1,
 859         &iPartIdxLabel, pPrior, r1);
 860     sqlite3VdbeAddOp3(v, OP_IdxDelete, iIdxCur+i, r1,
 861         pIdx->uniqNotNull ? pIdx->nKeyCol : pIdx->nColumn);
 862     sqlite3ResolvePartIdxLabel(pParse, iPartIdxLabel);
 863     pPrior = pIdx;
 864   }
 865 }
 866
 867 /*
 868 ** Generate code that will assemble an index key and stores it in register
 869 ** regOut.  The key with be for index pIdx which is an index on pTab.
 870 ** iCur is the index of a cursor open on the pTab table and pointing to
 871 ** the entry that needs indexing.  If pTab is a WITHOUT ROWID table, then
 872 ** iCur must be the cursor of the PRIMARY KEY index.
 873 **
 874 ** Return a register number which is the first in a block of
 875 ** registers that holds the elements of the index key.  The
 876 ** block of registers has already been deallocated by the time
 877 ** this routine returns.
 878 **
 879 ** If *piPartIdxLabel is not NULL, fill it in with a label and jump
 880 ** to that label if pIdx is a partial index that should be skipped.
 881 ** The label should be resolved using sqlite3ResolvePartIdxLabel().
 882 ** A partial index should be skipped if its WHERE clause evaluates
 883 ** to false or null.  If pIdx is not a partial index, *piPartIdxLabel
 884 ** will be set to zero which is an empty label that is ignored by
 885 ** sqlite3ResolvePartIdxLabel().
 886 **
 887 ** The pPrior and regPrior parameters are used to implement a cache to
 888 ** avoid unnecessary register loads.  If pPrior is not NULL, then it is
 889 ** a pointer to a different index for which an index key has just been
 890 ** computed into register regPrior.  If the current pIdx index is generating
 891 ** its key into the same sequence of registers and if pPrior and pIdx share
 892 ** a column in common, then the register corresponding to that column already
 893 ** holds the correct value and the loading of that register is skipped.
 894 ** This optimization is helpful when doing a DELETE or an INTEGRITY_CHECK
 895 ** on a table with multiple indices, and especially with the ROWID or
 896 ** PRIMARY KEY columns of the index.
 897 */
 898 int sqlite3GenerateIndexKey(
 899   Parse *pParse,       /* Parsing context */
 900   Index *pIdx,         /* The index for which to generate a key */
 901   int iDataCur,        /* Cursor number from which to take column data */
 902   int regOut,          /* Put the new key into this register if not 0 */
 903   int prefixOnly,      /* Compute only a unique prefix of the key */
 904   int *piPartIdxLabel, /* OUT: Jump to this label to skip partial index */
 905   Index *pPrior,       /* Previously generated index key */
 906   int regPrior         /* Register holding previous generated key */
 907 ){
 908   Vdbe *v = pParse->pVdbe;
 909   int j;
 910   int regBase;
 911   int nCol;
 912
 913   if( piPartIdxLabel ){
 914     if( pIdx->pPartIdxWhere ){
 915       *piPartIdxLabel = sqlite3VdbeMakeLabel(pParse);
 916       pParse->iSelfTab = iDataCur + 1;
 917       sqlite3ExprIfFalseDup(pParse, pIdx->pPartIdxWhere, *piPartIdxLabel,
 918                             SQLITE_JUMPIFNULL);
 919       pParse->iSelfTab = 0;
 920     }else{
 921       *piPartIdxLabel = 0;
 922     }
 923   }
 924   nCol = (prefixOnly && pIdx->uniqNotNull) ? pIdx->nKeyCol : pIdx->nColumn;
 925   regBase = sqlite3GetTempRange(pParse, nCol);
 926   if( pPrior && (regBase!=regPrior || pPrior->pPartIdxWhere) ) pPrior = 0;
 927   for(j=0; j<nCol; j++){
 928     if( pPrior
 929      && pPrior->aiColumn[j]==pIdx->aiColumn[j]
 930      && pPrior->aiColumn[j]!=XN_EXPR
 931     ){
 932       /* This column was already computed by the previous index */
 933       continue;
 934     }
 935     sqlite3ExprCodeLoadIndexColumn(pParse, pIdx, iDataCur, j, regBase+j);
 936     /* If the column affinity is REAL but the number is an integer, then it
 937     ** might be stored in the table as an integer (using a compact
 938     ** representation) then converted to REAL by an OP_RealAffinity opcode.
 939     ** But we are getting ready to store this value back into an index, where
 940     ** it should be converted by to INTEGER again.  So omit the OP_RealAffinity
 941     ** opcode if it is present */
 942     sqlite3VdbeDeletePriorOpcode(v, OP_RealAffinity);
 943   }
 944   if( regOut ){
 945     sqlite3VdbeAddOp3(v, OP_MakeRecord, regBase, nCol, regOut);
 946     if( pIdx->pTable->pSelect ){
 947       const char *zAff = sqlite3IndexAffinityStr(pParse->db, pIdx);
 948       sqlite3VdbeChangeP4(v, -1, zAff, P4_TRANSIENT);
 949     }
 950   }
 951   sqlite3ReleaseTempRange(pParse, regBase, nCol);
 952   return regBase;
 953 }
 954
 955 /*
 956 ** If a prior call to sqlite3GenerateIndexKey() generated a jump-over label
 957 ** because it was a partial index, then this routine should be called to
 958 ** resolve that label.
 959 */
 960 void sqlite3ResolvePartIdxLabel(Parse *pParse, int iLabel){
 961   if( iLabel ){
 962     sqlite3VdbeResolveLabel(pParse->pVdbe, iLabel);
 963   }
 964 }