src/update.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 ** to handle UPDATE statements.
  14 */
  15 #include "sqliteInt.h"
  16
  17 #ifndef SQLITE_OMIT_VIRTUALTABLE
  18 /* Forward declaration */
  19 static void updateVirtualTable(
  20   Parse *pParse,       /* The parsing context */
  21   SrcList *pSrc,       /* The virtual table to be modified */
  22   Table *pTab,         /* The virtual table */
  23   ExprList *pChanges,  /* The columns to change in the UPDATE statement */
  24   Expr *pRowidExpr,    /* Expression used to recompute the rowid */
  25   int *aXRef,          /* Mapping from columns of pTab to entries in pChanges */
  26   Expr *pWhere,        /* WHERE clause of the UPDATE statement */
  27   int onError          /* ON CONFLICT strategy */
  28 );
  29 #endif /* SQLITE_OMIT_VIRTUALTABLE */
  30
  31 /*
  32 ** The most recently coded instruction was an OP_Column to retrieve the
  33 ** i-th column of table pTab. This routine sets the P4 parameter of the
  34 ** OP_Column to the default value, if any.
  35 **
  36 ** The default value of a column is specified by a DEFAULT clause in the
  37 ** column definition. This was either supplied by the user when the table
  38 ** was created, or added later to the table definition by an ALTER TABLE
  39 ** command. If the latter, then the row-records in the table btree on disk
  40 ** may not contain a value for the column and the default value, taken
  41 ** from the P4 parameter of the OP_Column instruction, is returned instead.
  42 ** If the former, then all row-records are guaranteed to include a value
  43 ** for the column and the P4 value is not required.
  44 **
  45 ** Column definitions created by an ALTER TABLE command may only have
  46 ** literal default values specified: a number, null or a string. (If a more
  47 ** complicated default expression value was provided, it is evaluated
  48 ** when the ALTER TABLE is executed and one of the literal values written
  49 ** into the sqlite_schema table.)
  50 **
  51 ** Therefore, the P4 parameter is only required if the default value for
  52 ** the column is a literal number, string or null. The sqlite3ValueFromExpr()
  53 ** function is capable of transforming these types of expressions into
  54 ** sqlite3_value objects.
  55 **
  56 ** If column as REAL affinity and the table is an ordinary b-tree table
  57 ** (not a virtual table) then the value might have been stored as an
  58 ** integer.  In that case, add an OP_RealAffinity opcode to make sure
  59 ** it has been converted into REAL.
  60 */
  61 void sqlite3ColumnDefault(Vdbe *v, Table *pTab, int i, int iReg){
  62   Column *pCol;
  63   assert( pTab!=0 );
  64   assert( pTab->nCol>i );
  65   pCol = &pTab->aCol[i];
  66   if( pCol->iDflt ){
  67     sqlite3_value *pValue = 0;
  68     u8 enc = ENC(sqlite3VdbeDb(v));
  69     assert( !IsView(pTab) );
  70     VdbeComment((v, "%s.%s", pTab->zName, pCol->zCnName));
  71     assert( i<pTab->nCol );
  72     sqlite3ValueFromExpr(sqlite3VdbeDb(v),
  73                          sqlite3ColumnExpr(pTab,pCol), enc,
  74                          pCol->affinity, &pValue);
  75     if( pValue ){
  76       sqlite3VdbeAppendP4(v, pValue, P4_MEM);
  77     }
  78   }
  79 #ifndef SQLITE_OMIT_FLOATING_POINT
  80   if( pCol->affinity==SQLITE_AFF_REAL && !IsVirtual(pTab) ){
  81     sqlite3VdbeAddOp1(v, OP_RealAffinity, iReg);
  82   }
  83 #endif
  84 }
  85
  86 /*
  87 ** Check to see if column iCol of index pIdx references any of the
  88 ** columns defined by aXRef and chngRowid.  Return true if it does
  89 ** and false if not.  This is an optimization.  False-positives are a
  90 ** performance degradation, but false-negatives can result in a corrupt
  91 ** index and incorrect answers.
  92 **
  93 ** aXRef[j] will be non-negative if column j of the original table is
  94 ** being updated.  chngRowid will be true if the rowid of the table is
  95 ** being updated.
  96 */
  97 static int indexColumnIsBeingUpdated(
  98   Index *pIdx,      /* The index to check */
  99   int iCol,         /* Which column of the index to check */
 100   int *aXRef,       /* aXRef[j]>=0 if column j is being updated */
 101   int chngRowid     /* true if the rowid is being updated */
 102 ){
 103   i16 iIdxCol = pIdx->aiColumn[iCol];
 104   assert( iIdxCol!=XN_ROWID ); /* Cannot index rowid */
 105   if( iIdxCol>=0 ){
 106     return aXRef[iIdxCol]>=0;
 107   }
 108   assert( iIdxCol==XN_EXPR );
 109   assert( pIdx->aColExpr!=0 );
 110   assert( pIdx->aColExpr->a[iCol].pExpr!=0 );
 111   return sqlite3ExprReferencesUpdatedColumn(pIdx->aColExpr->a[iCol].pExpr,
 112                                             aXRef,chngRowid);
 113 }
 114
 115 /*
 116 ** Check to see if index pIdx is a partial index whose conditional
 117 ** expression might change values due to an UPDATE.  Return true if
 118 ** the index is subject to change and false if the index is guaranteed
 119 ** to be unchanged.  This is an optimization.  False-positives are a
 120 ** performance degradation, but false-negatives can result in a corrupt
 121 ** index and incorrect answers.
 122 **
 123 ** aXRef[j] will be non-negative if column j of the original table is
 124 ** being updated.  chngRowid will be true if the rowid of the table is
 125 ** being updated.
 126 */
 127 static int indexWhereClauseMightChange(
 128   Index *pIdx,      /* The index to check */
 129   int *aXRef,       /* aXRef[j]>=0 if column j is being updated */
 130   int chngRowid     /* true if the rowid is being updated */
 131 ){
 132   if( pIdx->pPartIdxWhere==0 ) return 0;
 133   return sqlite3ExprReferencesUpdatedColumn(pIdx->pPartIdxWhere,
 134                                             aXRef, chngRowid);
 135 }
 136
 137 /*
 138 ** Allocate and return a pointer to an expression of type TK_ROW with
 139 ** Expr.iColumn set to value (iCol+1). The resolver will modify the
 140 ** expression to be a TK_COLUMN reading column iCol of the first
 141 ** table in the source-list (pSrc->a[0]).
 142 */
 143 static Expr *exprRowColumn(Parse *pParse, int iCol){
 144   Expr *pRet = sqlite3PExpr(pParse, TK_ROW, 0, 0);
 145   if( pRet ) pRet->iColumn = iCol+1;
 146   return pRet;
 147 }
 148
 149 /*
 150 ** Assuming both the pLimit and pOrderBy parameters are NULL, this function
 151 ** generates VM code to run the query:
 152 **
 153 **   SELECT <other-columns>, pChanges FROM pTabList WHERE pWhere
 154 **
 155 ** and write the results to the ephemeral table already opened as cursor
 156 ** iEph. None of pChanges, pTabList or pWhere are modified or consumed by
 157 ** this function, they must be deleted by the caller.
 158 **
 159 ** Or, if pLimit and pOrderBy are not NULL, and pTab is not a view:
 160 **
 161 **   SELECT <other-columns>, pChanges FROM pTabList
 162 **   WHERE pWhere
 163 **   GROUP BY <other-columns>
 164 **   ORDER BY pOrderBy LIMIT pLimit
 165 **
 166 ** If pTab is a view, the GROUP BY clause is omitted.
 167 **
 168 ** Exactly how results are written to table iEph, and exactly what
 169 ** the <other-columns> in the query above are is determined by the type
 170 ** of table pTabList->a[0].pTab.
 171 **
 172 ** If the table is a WITHOUT ROWID table, then argument pPk must be its
 173 ** PRIMARY KEY. In this case <other-columns> are the primary key columns
 174 ** of the table, in order. The results of the query are written to ephemeral
 175 ** table iEph as index keys, using OP_IdxInsert.
 176 **
 177 ** If the table is actually a view, then <other-columns> are all columns of
 178 ** the view. The results are written to the ephemeral table iEph as records
 179 ** with automatically assigned integer keys.
 180 **
 181 ** If the table is a virtual or ordinary intkey table, then <other-columns>
 182 ** is its rowid. For a virtual table, the results are written to iEph as
 183 ** records with automatically assigned integer keys For intkey tables, the
 184 ** rowid value in <other-columns> is used as the integer key, and the
 185 ** remaining fields make up the table record.
 186 */
 187 static void updateFromSelect(
 188   Parse *pParse,                  /* Parse context */
 189   int iEph,                       /* Cursor for open eph. table */
 190   Index *pPk,                     /* PK if table 0 is WITHOUT ROWID */
 191   ExprList *pChanges,             /* List of expressions to return */
 192   SrcList *pTabList,              /* List of tables to select from */
 193   Expr *pWhere,                   /* WHERE clause for query */
 194   ExprList *pOrderBy,             /* ORDER BY clause */
 195   Expr *pLimit                    /* LIMIT clause */
 196 ){
 197   int i;
 198   SelectDest dest;
 199   Select *pSelect = 0;
 200   ExprList *pList = 0;
 201   ExprList *pGrp = 0;
 202   Expr *pLimit2 = 0;
 203   ExprList *pOrderBy2 = 0;
 204   sqlite3 *db = pParse->db;
 205   Table *pTab = pTabList->a[0].pTab;
 206   SrcList *pSrc;
 207   Expr *pWhere2;
 208   int eDest;
 209
 210 #ifdef SQLITE_ENABLE_UPDATE_DELETE_LIMIT
 211   if( pOrderBy && pLimit==0 ) {
 212     sqlite3ErrorMsg(pParse, "ORDER BY without LIMIT on UPDATE");
 213     return;
 214   }
 215   pOrderBy2 = sqlite3ExprListDup(db, pOrderBy, 0);
 216   pLimit2 = sqlite3ExprDup(db, pLimit, 0);
 217 #else
 218   UNUSED_PARAMETER(pOrderBy);
 219   UNUSED_PARAMETER(pLimit);
 220 #endif
 221
 222   pSrc = sqlite3SrcListDup(db, pTabList, 0);
 223   pWhere2 = sqlite3ExprDup(db, pWhere, 0);
 224
 225   assert( pTabList->nSrc>1 );
 226   if( pSrc ){
 227     assert( pSrc->a[0].fg.notCte );
 228     pSrc->a[0].iCursor = -1;
 229     pSrc->a[0].pTab->nTabRef--;
 230     pSrc->a[0].pTab = 0;
 231   }
 232   if( pPk ){
 233     for(i=0; i<pPk->nKeyCol; i++){
 234       Expr *pNew = exprRowColumn(pParse, pPk->aiColumn[i]);
 235 #ifdef SQLITE_ENABLE_UPDATE_DELETE_LIMIT
 236       if( pLimit ){
 237         pGrp = sqlite3ExprListAppend(pParse, pGrp, sqlite3ExprDup(db, pNew, 0));
 238       }
 239 #endif
 240       pList = sqlite3ExprListAppend(pParse, pList, pNew);
 241     }
 242     eDest = IsVirtual(pTab) ? SRT_Table : SRT_Upfrom;
 243   }else if( IsView(pTab) ){
 244     for(i=0; i<pTab->nCol; i++){
 245       pList = sqlite3ExprListAppend(pParse, pList, exprRowColumn(pParse, i));
 246     }
 247     eDest = SRT_Table;
 248   }else{
 249     eDest = IsVirtual(pTab) ? SRT_Table : SRT_Upfrom;
 250     pList = sqlite3ExprListAppend(pParse, 0, sqlite3PExpr(pParse,TK_ROW,0,0));
 251 #ifdef SQLITE_ENABLE_UPDATE_DELETE_LIMIT
 252     if( pLimit ){
 253       pGrp = sqlite3ExprListAppend(pParse, 0, sqlite3PExpr(pParse,TK_ROW,0,0));
 254     }
 255 #endif
 256   }
 257   assert( pChanges!=0 || pParse->db->mallocFailed );
 258   if( pChanges ){
 259     for(i=0; i<pChanges->nExpr; i++){
 260       pList = sqlite3ExprListAppend(pParse, pList,
 261           sqlite3ExprDup(db, pChanges->a[i].pExpr, 0)
 262       );
 263     }
 264   }
 265   pSelect = sqlite3SelectNew(pParse, pList,
 266       pSrc, pWhere2, pGrp, 0, pOrderBy2,
 267       SF_UFSrcCheck|SF_IncludeHidden|SF_UpdateFrom, pLimit2
 268   );
 269   if( pSelect ) pSelect->selFlags |= SF_OrderByReqd;
 270   sqlite3SelectDestInit(&dest, eDest, iEph);
 271   dest.iSDParm2 = (pPk ? pPk->nKeyCol : -1);
 272   sqlite3Select(pParse, pSelect, &dest);
 273   sqlite3SelectDelete(db, pSelect);
 274 }
 275
 276 /*
 277 ** Process an UPDATE statement.
 278 **
 279 **   UPDATE OR IGNORE tbl SET a=b, c=d FROM tbl2... WHERE e<5 AND f NOT NULL;
 280 **          \_______/ \_/     \______/      \_____/       \________________/
 281 **           onError   |      pChanges         |                pWhere
 282 **                     \_______________________/
 283 **                               pTabList
 284 */
 285 void sqlite3Update(
 286   Parse *pParse,         /* The parser context */
 287   SrcList *pTabList,     /* The table in which we should change things */
 288   ExprList *pChanges,    /* Things to be changed */
 289   Expr *pWhere,          /* The WHERE clause.  May be null */
 290   int onError,           /* How to handle constraint errors */
 291   ExprList *pOrderBy,    /* ORDER BY clause. May be null */
 292   Expr *pLimit,          /* LIMIT clause. May be null */
 293   Upsert *pUpsert        /* ON CONFLICT clause, or null */
 294 ){
 295   int i, j, k;           /* Loop counters */
 296   Table *pTab;           /* The table to be updated */
 297   int addrTop = 0;       /* VDBE instruction address of the start of the loop */
 298   WhereInfo *pWInfo = 0; /* Information about the WHERE clause */
 299   Vdbe *v;               /* The virtual database engine */
 300   Index *pIdx;           /* For looping over indices */
 301   Index *pPk;            /* The PRIMARY KEY index for WITHOUT ROWID tables */
 302   int nIdx;              /* Number of indices that need updating */
 303   int nAllIdx;           /* Total number of indexes */
 304   int iBaseCur;          /* Base cursor number */
 305   int iDataCur;          /* Cursor for the canonical data btree */
 306   int iIdxCur;           /* Cursor for the first index */
 307   sqlite3 *db;           /* The database structure */
 308   int *aRegIdx = 0;      /* Registers for to each index and the main table */
 309   int *aXRef = 0;        /* aXRef[i] is the index in pChanges->a[] of the
 310                          ** an expression for the i-th column of the table.
 311                          ** aXRef[i]==-1 if the i-th column is not changed. */
 312   u8 *aToOpen;           /* 1 for tables and indices to be opened */
 313   u8 chngPk;             /* PRIMARY KEY changed in a WITHOUT ROWID table */
 314   u8 chngRowid;          /* Rowid changed in a normal table */
 315   u8 chngKey;            /* Either chngPk or chngRowid */
 316   Expr *pRowidExpr = 0;  /* Expression defining the new record number */
 317   int iRowidExpr = -1;   /* Index of "rowid=" (or IPK) assignment in pChanges */
 318   AuthContext sContext;  /* The authorization context */
 319   NameContext sNC;       /* The name-context to resolve expressions in */
 320   int iDb;               /* Database containing the table being updated */
 321   int eOnePass;          /* ONEPASS_XXX value from where.c */
 322   int hasFK;             /* True if foreign key processing is required */
 323   int labelBreak;        /* Jump here to break out of UPDATE loop */
 324   int labelContinue;     /* Jump here to continue next step of UPDATE loop */
 325   int flags;             /* Flags for sqlite3WhereBegin() */
 326
 327 #ifndef SQLITE_OMIT_TRIGGER
 328   int isView;            /* True when updating a view (INSTEAD OF trigger) */
 329   Trigger *pTrigger;     /* List of triggers on pTab, if required */
 330   int tmask;             /* Mask of TRIGGER_BEFORE|TRIGGER_AFTER */
 331 #endif
 332   int newmask;           /* Mask of NEW.* columns accessed by BEFORE triggers */
 333   int iEph = 0;          /* Ephemeral table holding all primary key values */
 334   int nKey = 0;          /* Number of elements in regKey for WITHOUT ROWID */
 335   int aiCurOnePass[2];   /* The write cursors opened by WHERE_ONEPASS */
 336   int addrOpen = 0;      /* Address of OP_OpenEphemeral */
 337   int iPk = 0;           /* First of nPk cells holding PRIMARY KEY value */
 338   i16 nPk = 0;           /* Number of components of the PRIMARY KEY */
 339   int bReplace = 0;      /* True if REPLACE conflict resolution might happen */
 340   int bFinishSeek = 1;   /* The OP_FinishSeek opcode is needed */
 341   int nChangeFrom = 0;   /* If there is a FROM, pChanges->nExpr, else 0 */
 342
 343   /* Register Allocations */
 344   int regRowCount = 0;   /* A count of rows changed */
 345   int regOldRowid = 0;   /* The old rowid */
 346   int regNewRowid = 0;   /* The new rowid */
 347   int regNew = 0;        /* Content of the NEW.* table in triggers */
 348   int regOld = 0;        /* Content of OLD.* table in triggers */
 349   int regRowSet = 0;     /* Rowset of rows to be updated */
 350   int regKey = 0;        /* composite PRIMARY KEY value */
 351
 352   memset(&sContext, 0, sizeof(sContext));
 353   db = pParse->db;
 354   assert( db->pParse==pParse );
 355   if( pParse->nErr ){
 356     goto update_cleanup;
 357   }
 358   assert( db->mallocFailed==0 );
 359
 360   /* Locate the table which we want to update.
 361   */
 362   pTab = sqlite3SrcListLookup(pParse, pTabList);
 363   if( pTab==0 ) goto update_cleanup;
 364   iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
 365
 366   /* Figure out if we have any triggers and if the table being
 367   ** updated is a view.
 368   */
 369 #ifndef SQLITE_OMIT_TRIGGER
 370   pTrigger = sqlite3TriggersExist(pParse, pTab, TK_UPDATE, pChanges, &tmask);
 371   isView = IsView(pTab);
 372   assert( pTrigger || tmask==0 );
 373 #else
 374 # define pTrigger 0
 375 # define isView 0
 376 # define tmask 0
 377 #endif
 378 #ifdef SQLITE_OMIT_VIEW
 379 # undef isView
 380 # define isView 0
 381 #endif
 382
 383 #if TREETRACE_ENABLED
 384   if( sqlite3TreeTrace & 0x10000 ){
 385     sqlite3TreeViewLine(0, "In sqlite3Update() at %s:%d", __FILE__, __LINE__);
 386     sqlite3TreeViewUpdate(pParse->pWith, pTabList, pChanges, pWhere,
 387                           onError, pOrderBy, pLimit, pUpsert, pTrigger);
 388   }
 389 #endif
 390
 391   /* If there was a FROM clause, set nChangeFrom to the number of expressions
 392   ** in the change-list. Otherwise, set it to 0. There cannot be a FROM
 393   ** clause if this function is being called to generate code for part of
 394   ** an UPSERT statement.  */
 395   nChangeFrom = (pTabList->nSrc>1) ? pChanges->nExpr : 0;
 396   assert( nChangeFrom==0 || pUpsert==0 );
 397
 398 #ifdef SQLITE_ENABLE_UPDATE_DELETE_LIMIT
 399   if( !isView && nChangeFrom==0 ){
 400     pWhere = sqlite3LimitWhere(
 401         pParse, pTabList, pWhere, pOrderBy, pLimit, "UPDATE"
 402     );
 403     pOrderBy = 0;
 404     pLimit = 0;
 405   }
 406 #endif
 407
 408   if( sqlite3ViewGetColumnNames(pParse, pTab) ){
 409     goto update_cleanup;
 410   }
 411   if( sqlite3IsReadOnly(pParse, pTab, pTrigger) ){
 412     goto update_cleanup;
 413   }
 414
 415   /* Allocate a cursors for the main database table and for all indices.
 416   ** The index cursors might not be used, but if they are used they
 417   ** need to occur right after the database cursor.  So go ahead and
 418   ** allocate enough space, just in case.
 419   */
 420   iBaseCur = iDataCur = pParse->nTab++;
 421   iIdxCur = iDataCur+1;
 422   pPk = HasRowid(pTab) ? 0 : sqlite3PrimaryKeyIndex(pTab);
 423   testcase( pPk!=0 && pPk!=pTab->pIndex );
 424   for(nIdx=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, nIdx++){
 425     if( pPk==pIdx ){
 426       iDataCur = pParse->nTab;
 427     }
 428     pParse->nTab++;
 429   }
 430   if( pUpsert ){
 431     /* On an UPSERT, reuse the same cursors already opened by INSERT */
 432     iDataCur = pUpsert->iDataCur;
 433     iIdxCur = pUpsert->iIdxCur;
 434     pParse->nTab = iBaseCur;
 435   }
 436   pTabList->a[0].iCursor = iDataCur;
 437
 438   /* Allocate space for aXRef[], aRegIdx[], and aToOpen[].
 439   ** Initialize aXRef[] and aToOpen[] to their default values.
 440   */
 441   aXRef = sqlite3DbMallocRawNN(db, sizeof(int) * (pTab->nCol+nIdx+1) + nIdx+2 );
 442   if( aXRef==0 ) goto update_cleanup;
 443   aRegIdx = aXRef+pTab->nCol;
 444   aToOpen = (u8*)(aRegIdx+nIdx+1);
 445   memset(aToOpen, 1, nIdx+1);
 446   aToOpen[nIdx+1] = 0;
 447   for(i=0; i<pTab->nCol; i++) aXRef[i] = -1;
 448
 449   /* Initialize the name-context */
 450   memset(&sNC, 0, sizeof(sNC));
 451   sNC.pParse = pParse;
 452   sNC.pSrcList = pTabList;
 453   sNC.uNC.pUpsert = pUpsert;
 454   sNC.ncFlags = NC_UUpsert;
 455
 456   /* Begin generating code. */
 457   v = sqlite3GetVdbe(pParse);
 458   if( v==0 ) goto update_cleanup;
 459
 460   /* Resolve the column names in all the expressions of the
 461   ** of the UPDATE statement.  Also find the column index
 462   ** for each column to be updated in the pChanges array.  For each
 463   ** column to be updated, make sure we have authorization to change
 464   ** that column.
 465   */
 466   chngRowid = chngPk = 0;
 467   for(i=0; i<pChanges->nExpr; i++){
 468     u8 hCol = sqlite3StrIHash(pChanges->a[i].zEName);
 469     /* If this is an UPDATE with a FROM clause, do not resolve expressions
 470     ** here. The call to sqlite3Select() below will do that. */
 471     if( nChangeFrom==0 && sqlite3ResolveExprNames(&sNC, pChanges->a[i].pExpr) ){
 472       goto update_cleanup;
 473     }
 474     for(j=0; j<pTab->nCol; j++){
 475       if( pTab->aCol[j].hName==hCol
 476        && sqlite3StrICmp(pTab->aCol[j].zCnName, pChanges->a[i].zEName)==0
 477       ){
 478         if( j==pTab->iPKey ){
 479           chngRowid = 1;
 480           pRowidExpr = pChanges->a[i].pExpr;
 481           iRowidExpr = i;
 482         }else if( pPk && (pTab->aCol[j].colFlags & COLFLAG_PRIMKEY)!=0 ){
 483           chngPk = 1;
 484         }
 485 #ifndef SQLITE_OMIT_GENERATED_COLUMNS
 486         else if( pTab->aCol[j].colFlags & COLFLAG_GENERATED ){
 487           testcase( pTab->aCol[j].colFlags & COLFLAG_VIRTUAL );
 488           testcase( pTab->aCol[j].colFlags & COLFLAG_STORED );
 489           sqlite3ErrorMsg(pParse,
 490              "cannot UPDATE generated column \"%s\"",
 491              pTab->aCol[j].zCnName);
 492           goto update_cleanup;
 493         }
 494 #endif
 495         aXRef[j] = i;
 496         break;
 497       }
 498     }
 499     if( j>=pTab->nCol ){
 500       if( pPk==0 && sqlite3IsRowid(pChanges->a[i].zEName) ){
 501         j = -1;
 502         chngRowid = 1;
 503         pRowidExpr = pChanges->a[i].pExpr;
 504         iRowidExpr = i;
 505       }else{
 506         sqlite3ErrorMsg(pParse, "no such column: %s", pChanges->a[i].zEName);
 507         pParse->checkSchema = 1;
 508         goto update_cleanup;
 509       }
 510     }
 511 #ifndef SQLITE_OMIT_AUTHORIZATION
 512     {
 513       int rc;
 514       rc = sqlite3AuthCheck(pParse, SQLITE_UPDATE, pTab->zName,
 515                             j<0 ? "ROWID" : pTab->aCol[j].zCnName,
 516                             db->aDb[iDb].zDbSName);
 517       if( rc==SQLITE_DENY ){
 518         goto update_cleanup;
 519       }else if( rc==SQLITE_IGNORE ){
 520         aXRef[j] = -1;
 521       }
 522     }
 523 #endif
 524   }
 525   assert( (chngRowid & chngPk)==0 );
 526   assert( chngRowid==0 || chngRowid==1 );
 527   assert( chngPk==0 || chngPk==1 );
 528   chngKey = chngRowid + chngPk;
 529
 530 #ifndef SQLITE_OMIT_GENERATED_COLUMNS
 531   /* Mark generated columns as changing if their generator expressions
 532   ** reference any changing column.  The actual aXRef[] value for
 533   ** generated expressions is not used, other than to check to see that it
 534   ** is non-negative, so the value of aXRef[] for generated columns can be
 535   ** set to any non-negative number.  We use 99999 so that the value is
 536   ** obvious when looking at aXRef[] in a symbolic debugger.
 537   */
 538   if( pTab->tabFlags & TF_HasGenerated ){
 539     int bProgress;
 540     testcase( pTab->tabFlags & TF_HasVirtual );
 541     testcase( pTab->tabFlags & TF_HasStored );
 542     do{
 543       bProgress = 0;
 544       for(i=0; i<pTab->nCol; i++){
 545         if( aXRef[i]>=0 ) continue;
 546         if( (pTab->aCol[i].colFlags & COLFLAG_GENERATED)==0 ) continue;
 547         if( sqlite3ExprReferencesUpdatedColumn(
 548                 sqlite3ColumnExpr(pTab, &pTab->aCol[i]),
 549                  aXRef, chngRowid)
 550         ){
 551           aXRef[i] = 99999;
 552           bProgress = 1;
 553         }
 554       }
 555     }while( bProgress );
 556   }
 557 #endif
 558
 559   /* The SET expressions are not actually used inside the WHERE loop.
 560   ** So reset the colUsed mask. Unless this is a virtual table. In that
 561   ** case, set all bits of the colUsed mask (to ensure that the virtual
 562   ** table implementation makes all columns available).
 563   */
 564   pTabList->a[0].colUsed = IsVirtual(pTab) ? ALLBITS : 0;
 565
 566   hasFK = sqlite3FkRequired(pParse, pTab, aXRef, chngKey);
 567
 568   /* There is one entry in the aRegIdx[] array for each index on the table
 569   ** being updated.  Fill in aRegIdx[] with a register number that will hold
 570   ** the key for accessing each index.
 571   */
 572   if( onError==OE_Replace ) bReplace = 1;
 573   for(nAllIdx=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, nAllIdx++){
 574     int reg;
 575     if( chngKey || hasFK>1 || pIdx==pPk
 576      || indexWhereClauseMightChange(pIdx,aXRef,chngRowid)
 577     ){
 578       reg = ++pParse->nMem;
 579       pParse->nMem += pIdx->nColumn;
 580     }else{
 581       reg = 0;
 582       for(i=0; i<pIdx->nKeyCol; i++){
 583         if( indexColumnIsBeingUpdated(pIdx, i, aXRef, chngRowid) ){
 584           reg = ++pParse->nMem;
 585           pParse->nMem += pIdx->nColumn;
 586           if( onError==OE_Default && pIdx->onError==OE_Replace ){
 587             bReplace = 1;
 588           }
 589           break;
 590         }
 591       }
 592     }
 593     if( reg==0 ) aToOpen[nAllIdx+1] = 0;
 594     aRegIdx[nAllIdx] = reg;
 595   }
 596   aRegIdx[nAllIdx] = ++pParse->nMem;  /* Register storing the table record */
 597   if( bReplace ){
 598     /* If REPLACE conflict resolution might be invoked, open cursors on all
 599     ** indexes in case they are needed to delete records.  */
 600     memset(aToOpen, 1, nIdx+1);
 601   }
 602
 603   if( pParse->nested==0 ) sqlite3VdbeCountChanges(v);
 604   sqlite3BeginWriteOperation(pParse, pTrigger || hasFK, iDb);
 605
 606   /* Allocate required registers. */
 607   if( !IsVirtual(pTab) ){
 608     /* For now, regRowSet and aRegIdx[nAllIdx] share the same register.
 609     ** If regRowSet turns out to be needed, then aRegIdx[nAllIdx] will be
 610     ** reallocated.  aRegIdx[nAllIdx] is the register in which the main
 611     ** table record is written.  regRowSet holds the RowSet for the
 612     ** two-pass update algorithm. */
 613     assert( aRegIdx[nAllIdx]==pParse->nMem );
 614     regRowSet = aRegIdx[nAllIdx];
 615     regOldRowid = regNewRowid = ++pParse->nMem;
 616     if( chngPk || pTrigger || hasFK ){
 617       regOld = pParse->nMem + 1;
 618       pParse->nMem += pTab->nCol;
 619     }
 620     if( chngKey || pTrigger || hasFK ){
 621       regNewRowid = ++pParse->nMem;
 622     }
 623     regNew = pParse->nMem + 1;
 624     pParse->nMem += pTab->nCol;
 625   }
 626
 627   /* Start the view context. */
 628   if( isView ){
 629     sqlite3AuthContextPush(pParse, &sContext, pTab->zName);
 630   }
 631
 632   /* If we are trying to update a view, realize that view into
 633   ** an ephemeral table.
 634   */
 635 #if !defined(SQLITE_OMIT_VIEW) && !defined(SQLITE_OMIT_TRIGGER)
 636   if( nChangeFrom==0 && isView ){
 637     sqlite3MaterializeView(pParse, pTab,
 638         pWhere, pOrderBy, pLimit, iDataCur
 639     );
 640     pOrderBy = 0;
 641     pLimit = 0;
 642   }
 643 #endif
 644
 645   /* Resolve the column names in all the expressions in the
 646   ** WHERE clause.
 647   */
 648   if( nChangeFrom==0 && sqlite3ResolveExprNames(&sNC, pWhere) ){
 649     goto update_cleanup;
 650   }
 651
 652 #ifndef SQLITE_OMIT_VIRTUALTABLE
 653   /* Virtual tables must be handled separately */
 654   if( IsVirtual(pTab) ){
 655     updateVirtualTable(pParse, pTabList, pTab, pChanges, pRowidExpr, aXRef,
 656                        pWhere, onError);
 657     goto update_cleanup;
 658   }
 659 #endif
 660
 661   /* Jump to labelBreak to abandon further processing of this UPDATE */
 662   labelContinue = labelBreak = sqlite3VdbeMakeLabel(pParse);
 663
 664   /* Not an UPSERT.  Normal processing.  Begin by
 665   ** initialize the count of updated rows */
 666   if( (db->flags&SQLITE_CountRows)!=0
 667    && !pParse->pTriggerTab
 668    && !pParse->nested
 669    && !pParse->bReturning
 670    && pUpsert==0
 671   ){
 672     regRowCount = ++pParse->nMem;
 673     sqlite3VdbeAddOp2(v, OP_Integer, 0, regRowCount);
 674   }
 675
 676   if( nChangeFrom==0 && HasRowid(pTab) ){
 677     sqlite3VdbeAddOp3(v, OP_Null, 0, regRowSet, regOldRowid);
 678     iEph = pParse->nTab++;
 679     addrOpen = sqlite3VdbeAddOp3(v, OP_OpenEphemeral, iEph, 0, regRowSet);
 680   }else{
 681     assert( pPk!=0 || HasRowid(pTab) );
 682     nPk = pPk ? pPk->nKeyCol : 0;
 683     iPk = pParse->nMem+1;
 684     pParse->nMem += nPk;
 685     pParse->nMem += nChangeFrom;
 686     regKey = ++pParse->nMem;
 687     if( pUpsert==0 ){
 688       int nEphCol = nPk + nChangeFrom + (isView ? pTab->nCol : 0);
 689       iEph = pParse->nTab++;
 690       if( pPk ) sqlite3VdbeAddOp3(v, OP_Null, 0, iPk, iPk+nPk-1);
 691       addrOpen = sqlite3VdbeAddOp2(v, OP_OpenEphemeral, iEph, nEphCol);
 692       if( pPk ){
 693         KeyInfo *pKeyInfo = sqlite3KeyInfoOfIndex(pParse, pPk);
 694         if( pKeyInfo ){
 695           pKeyInfo->nAllField = nEphCol;
 696           sqlite3VdbeAppendP4(v, pKeyInfo, P4_KEYINFO);
 697         }
 698       }
 699       if( nChangeFrom ){
 700         updateFromSelect(
 701             pParse, iEph, pPk, pChanges, pTabList, pWhere, pOrderBy, pLimit
 702         );
 703 #ifndef SQLITE_OMIT_SUBQUERY
 704         if( isView ) iDataCur = iEph;
 705 #endif
 706       }
 707     }
 708   }
 709
 710   if( nChangeFrom ){
 711     sqlite3MultiWrite(pParse);
 712     eOnePass = ONEPASS_OFF;
 713     nKey = nPk;
 714     regKey = iPk;
 715   }else{
 716     if( pUpsert ){
 717       /* If this is an UPSERT, then all cursors have already been opened by
 718       ** the outer INSERT and the data cursor should be pointing at the row
 719       ** that is to be updated.  So bypass the code that searches for the
 720       ** row(s) to be updated.
 721       */
 722       pWInfo = 0;
 723       eOnePass = ONEPASS_SINGLE;
 724       sqlite3ExprIfFalse(pParse, pWhere, labelBreak, SQLITE_JUMPIFNULL);
 725       bFinishSeek = 0;
 726     }else{
 727       /* Begin the database scan.
 728       **
 729       ** Do not consider a single-pass strategy for a multi-row update if
 730       ** there is anything that might disrupt the cursor being used to do
 731       ** the UPDATE:
 732       **   (1) This is a nested UPDATE
 733       **   (2) There are triggers
 734       **   (3) There are FOREIGN KEY constraints
 735       **   (4) There are REPLACE conflict handlers
 736       **   (5) There are subqueries in the WHERE clause
 737       */
 738       flags = WHERE_ONEPASS_DESIRED;
 739       if( !pParse->nested
 740        && !pTrigger
 741        && !hasFK
 742        && !chngKey
 743        && !bReplace
 744        && (pWhere==0 || !ExprHasProperty(pWhere, EP_Subquery))
 745       ){
 746         flags |= WHERE_ONEPASS_MULTIROW;
 747       }
 748       pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere,0,0,0,flags,iIdxCur);
 749       if( pWInfo==0 ) goto update_cleanup;
 750
 751       /* A one-pass strategy that might update more than one row may not
 752       ** be used if any column of the index used for the scan is being
 753       ** updated. Otherwise, if there is an index on "b", statements like
 754       ** the following could create an infinite loop:
 755       **
 756       **   UPDATE t1 SET b=b+1 WHERE b>?
 757       **
 758       ** Fall back to ONEPASS_OFF if where.c has selected a ONEPASS_MULTI
 759       ** strategy that uses an index for which one or more columns are being
 760       ** updated.  */
 761       eOnePass = sqlite3WhereOkOnePass(pWInfo, aiCurOnePass);
 762       bFinishSeek = sqlite3WhereUsesDeferredSeek(pWInfo);
 763       if( eOnePass!=ONEPASS_SINGLE ){
 764         sqlite3MultiWrite(pParse);
 765         if( eOnePass==ONEPASS_MULTI ){
 766           int iCur = aiCurOnePass[1];
 767           if( iCur>=0 && iCur!=iDataCur && aToOpen[iCur-iBaseCur] ){
 768             eOnePass = ONEPASS_OFF;
 769           }
 770           assert( iCur!=iDataCur || !HasRowid(pTab) );
 771         }
 772       }
 773     }
 774
 775     if( HasRowid(pTab) ){
 776       /* Read the rowid of the current row of the WHERE scan. In ONEPASS_OFF
 777       ** mode, write the rowid into the FIFO. In either of the one-pass modes,
 778       ** leave it in register regOldRowid.  */
 779       sqlite3VdbeAddOp2(v, OP_Rowid, iDataCur, regOldRowid);
 780       if( eOnePass==ONEPASS_OFF ){
 781         aRegIdx[nAllIdx] = ++pParse->nMem;
 782         sqlite3VdbeAddOp3(v, OP_Insert, iEph, regRowSet, regOldRowid);
 783       }else{
 784         if( ALWAYS(addrOpen) ) sqlite3VdbeChangeToNoop(v, addrOpen);
 785       }
 786     }else{
 787       /* Read the PK of the current row into an array of registers. In
 788       ** ONEPASS_OFF mode, serialize the array into a record and store it in
 789       ** the ephemeral table. Or, in ONEPASS_SINGLE or MULTI mode, change
 790       ** the OP_OpenEphemeral instruction to a Noop (the ephemeral table
 791       ** is not required) and leave the PK fields in the array of registers.  */
 792       for(i=0; i<nPk; i++){
 793         assert( pPk->aiColumn[i]>=0 );
 794         sqlite3ExprCodeGetColumnOfTable(v, pTab, iDataCur,
 795                                         pPk->aiColumn[i], iPk+i);
 796       }
 797       if( eOnePass ){
 798         if( addrOpen ) sqlite3VdbeChangeToNoop(v, addrOpen);
 799         nKey = nPk;
 800         regKey = iPk;
 801       }else{
 802         sqlite3VdbeAddOp4(v, OP_MakeRecord, iPk, nPk, regKey,
 803                           sqlite3IndexAffinityStr(db, pPk), nPk);
 804         sqlite3VdbeAddOp4Int(v, OP_IdxInsert, iEph, regKey, iPk, nPk);
 805       }
 806     }
 807   }
 808
 809   if( pUpsert==0 ){
 810     if( nChangeFrom==0 && eOnePass!=ONEPASS_MULTI ){
 811       sqlite3WhereEnd(pWInfo);
 812     }
 813
 814     if( !isView ){
 815       int addrOnce = 0;
 816       int iNotUsed1 = 0;
 817       int iNotUsed2 = 0;
 818
 819       /* Open every index that needs updating. */
 820       if( eOnePass!=ONEPASS_OFF ){
 821         if( aiCurOnePass[0]>=0 ) aToOpen[aiCurOnePass[0]-iBaseCur] = 0;
 822         if( aiCurOnePass[1]>=0 ) aToOpen[aiCurOnePass[1]-iBaseCur] = 0;
 823       }
 824
 825       if( eOnePass==ONEPASS_MULTI && (nIdx-(aiCurOnePass[1]>=0))>0 ){
 826         addrOnce = sqlite3VdbeAddOp0(v, OP_Once); VdbeCoverage(v);
 827       }
 828       sqlite3OpenTableAndIndices(pParse, pTab, OP_OpenWrite, 0, iBaseCur,
 829                                  aToOpen, &iNotUsed1, &iNotUsed2);
 830       if( addrOnce ){
 831         sqlite3VdbeJumpHereOrPopInst(v, addrOnce);
 832       }
 833     }
 834
 835     /* Top of the update loop */
 836     if( eOnePass!=ONEPASS_OFF ){
 837       if( aiCurOnePass[0]!=iDataCur
 838        && aiCurOnePass[1]!=iDataCur
 839 #ifdef SQLITE_ALLOW_ROWID_IN_VIEW
 840        && !isView
 841 #endif
 842       ){
 843         assert( pPk );
 844         sqlite3VdbeAddOp4Int(v, OP_NotFound, iDataCur, labelBreak, regKey,nKey);
 845         VdbeCoverage(v);
 846       }
 847       if( eOnePass!=ONEPASS_SINGLE ){
 848         labelContinue = sqlite3VdbeMakeLabel(pParse);
 849       }
 850       sqlite3VdbeAddOp2(v, OP_IsNull, pPk ? regKey : regOldRowid, labelBreak);
 851       VdbeCoverageIf(v, pPk==0);
 852       VdbeCoverageIf(v, pPk!=0);
 853     }else if( pPk || nChangeFrom ){
 854       labelContinue = sqlite3VdbeMakeLabel(pParse);
 855       sqlite3VdbeAddOp2(v, OP_Rewind, iEph, labelBreak); VdbeCoverage(v);
 856       addrTop = sqlite3VdbeCurrentAddr(v);
 857       if( nChangeFrom ){
 858         if( !isView ){
 859           if( pPk ){
 860             for(i=0; i<nPk; i++){
 861               sqlite3VdbeAddOp3(v, OP_Column, iEph, i, iPk+i);
 862             }
 863             sqlite3VdbeAddOp4Int(
 864                 v, OP_NotFound, iDataCur, labelContinue, iPk, nPk
 865             ); VdbeCoverage(v);
 866           }else{
 867             sqlite3VdbeAddOp2(v, OP_Rowid, iEph, regOldRowid);
 868             sqlite3VdbeAddOp3(
 869                 v, OP_NotExists, iDataCur, labelContinue, regOldRowid
 870             ); VdbeCoverage(v);
 871           }
 872         }
 873       }else{
 874         sqlite3VdbeAddOp2(v, OP_RowData, iEph, regKey);
 875         sqlite3VdbeAddOp4Int(v, OP_NotFound, iDataCur, labelContinue, regKey,0);
 876         VdbeCoverage(v);
 877       }
 878     }else{
 879       sqlite3VdbeAddOp2(v, OP_Rewind, iEph, labelBreak); VdbeCoverage(v);
 880       labelContinue = sqlite3VdbeMakeLabel(pParse);
 881       addrTop = sqlite3VdbeAddOp2(v, OP_Rowid, iEph, regOldRowid);
 882       VdbeCoverage(v);
 883       sqlite3VdbeAddOp3(v, OP_NotExists, iDataCur, labelContinue, regOldRowid);
 884       VdbeCoverage(v);
 885     }
 886   }
 887
 888   /* If the rowid value will change, set register regNewRowid to
 889   ** contain the new value. If the rowid is not being modified,
 890   ** then regNewRowid is the same register as regOldRowid, which is
 891   ** already populated.  */
 892   assert( chngKey || pTrigger || hasFK || regOldRowid==regNewRowid );
 893   if( chngRowid ){
 894     assert( iRowidExpr>=0 );
 895     if( nChangeFrom==0 ){
 896       sqlite3ExprCode(pParse, pRowidExpr, regNewRowid);
 897     }else{
 898       sqlite3VdbeAddOp3(v, OP_Column, iEph, iRowidExpr, regNewRowid);
 899     }
 900     sqlite3VdbeAddOp1(v, OP_MustBeInt, regNewRowid); VdbeCoverage(v);
 901   }
 902
 903   /* Compute the old pre-UPDATE content of the row being changed, if that
 904   ** information is needed */
 905   if( chngPk || hasFK || pTrigger ){
 906     u32 oldmask = (hasFK ? sqlite3FkOldmask(pParse, pTab) : 0);
 907     oldmask |= sqlite3TriggerColmask(pParse,
 908         pTrigger, pChanges, 0, TRIGGER_BEFORE|TRIGGER_AFTER, pTab, onError
 909     );
 910     for(i=0; i<pTab->nCol; i++){
 911       u32 colFlags = pTab->aCol[i].colFlags;
 912       k = sqlite3TableColumnToStorage(pTab, i) + regOld;
 913       if( oldmask==0xffffffff
 914        || (i<32 && (oldmask & MASKBIT32(i))!=0)
 915        || (colFlags & COLFLAG_PRIMKEY)!=0
 916       ){
 917         testcase(  oldmask!=0xffffffff && i==31 );
 918         sqlite3ExprCodeGetColumnOfTable(v, pTab, iDataCur, i, k);
 919       }else{
 920         sqlite3VdbeAddOp2(v, OP_Null, 0, k);
 921       }
 922     }
 923     if( chngRowid==0 && pPk==0 ){
 924       sqlite3VdbeAddOp2(v, OP_Copy, regOldRowid, regNewRowid);
 925     }
 926   }
 927
 928   /* Populate the array of registers beginning at regNew with the new
 929   ** row data. This array is used to check constants, create the new
 930   ** table and index records, and as the values for any new.* references
 931   ** made by triggers.
 932   **
 933   ** If there are one or more BEFORE triggers, then do not populate the
 934   ** registers associated with columns that are (a) not modified by
 935   ** this UPDATE statement and (b) not accessed by new.* references. The
 936   ** values for registers not modified by the UPDATE must be reloaded from
 937   ** the database after the BEFORE triggers are fired anyway (as the trigger
 938   ** may have modified them). So not loading those that are not going to
 939   ** be used eliminates some redundant opcodes.
 940   */
 941   newmask = sqlite3TriggerColmask(
 942       pParse, pTrigger, pChanges, 1, TRIGGER_BEFORE, pTab, onError
 943   );
 944   for(i=0, k=regNew; i<pTab->nCol; i++, k++){
 945     if( i==pTab->iPKey ){
 946       sqlite3VdbeAddOp2(v, OP_Null, 0, k);
 947     }else if( (pTab->aCol[i].colFlags & COLFLAG_GENERATED)!=0 ){
 948       if( pTab->aCol[i].colFlags & COLFLAG_VIRTUAL ) k--;
 949     }else{
 950       j = aXRef[i];
 951       if( j>=0 ){
 952         if( nChangeFrom ){
 953           int nOff = (isView ? pTab->nCol : nPk);
 954           assert( eOnePass==ONEPASS_OFF );
 955           sqlite3VdbeAddOp3(v, OP_Column, iEph, nOff+j, k);
 956         }else{
 957           sqlite3ExprCode(pParse, pChanges->a[j].pExpr, k);
 958         }
 959       }else if( 0==(tmask&TRIGGER_BEFORE) || i>31 || (newmask & MASKBIT32(i)) ){
 960         /* This branch loads the value of a column that will not be changed
 961         ** into a register. This is done if there are no BEFORE triggers, or
 962         ** if there are one or more BEFORE triggers that use this value via
 963         ** a new.* reference in a trigger program.
 964         */
 965         testcase( i==31 );
 966         testcase( i==32 );
 967         sqlite3ExprCodeGetColumnOfTable(v, pTab, iDataCur, i, k);
 968         bFinishSeek = 0;
 969       }else{
 970         sqlite3VdbeAddOp2(v, OP_Null, 0, k);
 971       }
 972     }
 973   }
 974 #ifndef SQLITE_OMIT_GENERATED_COLUMNS
 975   if( pTab->tabFlags & TF_HasGenerated ){
 976     testcase( pTab->tabFlags & TF_HasVirtual );
 977     testcase( pTab->tabFlags & TF_HasStored );
 978     sqlite3ComputeGeneratedColumns(pParse, regNew, pTab);
 979   }
 980 #endif
 981
 982   /* Fire any BEFORE UPDATE triggers. This happens before constraints are
 983   ** verified. One could argue that this is wrong.
 984   */
 985   if( tmask&TRIGGER_BEFORE ){
 986     sqlite3TableAffinity(v, pTab, regNew);
 987     sqlite3CodeRowTrigger(pParse, pTrigger, TK_UPDATE, pChanges,
 988         TRIGGER_BEFORE, pTab, regOldRowid, onError, labelContinue);
 989
 990     if( !isView ){
 991       /* The row-trigger may have deleted the row being updated. In this
 992       ** case, jump to the next row. No updates or AFTER triggers are
 993       ** required. This behavior - what happens when the row being updated
 994       ** is deleted or renamed by a BEFORE trigger - is left undefined in the
 995       ** documentation.
 996       */
 997       if( pPk ){
 998         sqlite3VdbeAddOp4Int(v, OP_NotFound,iDataCur,labelContinue,regKey,nKey);
 999         VdbeCoverage(v);
1000       }else{
1001         sqlite3VdbeAddOp3(v, OP_NotExists, iDataCur, labelContinue,regOldRowid);
1002         VdbeCoverage(v);
1003       }
1004
1005       /* After-BEFORE-trigger-reload-loop:
1006       ** If it did not delete it, the BEFORE trigger may still have modified
1007       ** some of the columns of the row being updated. Load the values for
1008       ** all columns not modified by the update statement into their registers
1009       ** in case this has happened. Only unmodified columns are reloaded.
1010       ** The values computed for modified columns use the values before the
1011       ** BEFORE trigger runs.  See test case trigger1-18.0 (added 2018-04-26)
1012       ** for an example.
1013       */
1014       for(i=0, k=regNew; i<pTab->nCol; i++, k++){
1015         if( pTab->aCol[i].colFlags & COLFLAG_GENERATED ){
1016           if( pTab->aCol[i].colFlags & COLFLAG_VIRTUAL ) k--;
1017         }else if( aXRef[i]<0 && i!=pTab->iPKey ){
1018           sqlite3ExprCodeGetColumnOfTable(v, pTab, iDataCur, i, k);
1019         }
1020       }
1021 #ifndef SQLITE_OMIT_GENERATED_COLUMNS
1022       if( pTab->tabFlags & TF_HasGenerated ){
1023         testcase( pTab->tabFlags & TF_HasVirtual );
1024         testcase( pTab->tabFlags & TF_HasStored );
1025         sqlite3ComputeGeneratedColumns(pParse, regNew, pTab);
1026       }
1027 #endif
1028     }
1029   }
1030
1031   if( !isView ){
1032     /* Do constraint checks. */
1033     assert( regOldRowid>0 );
1034     sqlite3GenerateConstraintChecks(pParse, pTab, aRegIdx, iDataCur, iIdxCur,
1035         regNewRowid, regOldRowid, chngKey, onError, labelContinue, &bReplace,
1036         aXRef, 0);
1037
1038     /* If REPLACE conflict handling may have been used, or if the PK of the
1039     ** row is changing, then the GenerateConstraintChecks() above may have
1040     ** moved cursor iDataCur. Reseek it. */
1041     if( bReplace || chngKey ){
1042       if( pPk ){
1043         sqlite3VdbeAddOp4Int(v, OP_NotFound,iDataCur,labelContinue,regKey,nKey);
1044       }else{
1045         sqlite3VdbeAddOp3(v, OP_NotExists, iDataCur, labelContinue,regOldRowid);
1046       }
1047       VdbeCoverage(v);
1048     }
1049
1050     /* Do FK constraint checks. */
1051     if( hasFK ){
1052       sqlite3FkCheck(pParse, pTab, regOldRowid, 0, aXRef, chngKey);
1053     }
1054
1055     /* Delete the index entries associated with the current record.  */
1056     sqlite3GenerateRowIndexDelete(pParse, pTab, iDataCur, iIdxCur, aRegIdx, -1);
1057
1058     /* We must run the OP_FinishSeek opcode to resolve a prior
1059     ** OP_DeferredSeek if there is any possibility that there have been
1060     ** no OP_Column opcodes since the OP_DeferredSeek was issued.  But
1061     ** we want to avoid the OP_FinishSeek if possible, as running it
1062     ** costs CPU cycles. */
1063     if( bFinishSeek ){
1064       sqlite3VdbeAddOp1(v, OP_FinishSeek, iDataCur);
1065     }
1066
1067     /* If changing the rowid value, or if there are foreign key constraints
1068     ** to process, delete the old record. Otherwise, add a noop OP_Delete
1069     ** to invoke the pre-update hook.
1070     **
1071     ** That (regNew==regnewRowid+1) is true is also important for the
1072     ** pre-update hook. If the caller invokes preupdate_new(), the returned
1073     ** value is copied from memory cell (regNewRowid+1+iCol), where iCol
1074     ** is the column index supplied by the user.
1075     */
1076     assert( regNew==regNewRowid+1 );
1077 #ifdef SQLITE_ENABLE_PREUPDATE_HOOK
1078     sqlite3VdbeAddOp3(v, OP_Delete, iDataCur,
1079         OPFLAG_ISUPDATE | ((hasFK>1 || chngKey) ? 0 : OPFLAG_ISNOOP),
1080         regNewRowid
1081     );
1082     if( eOnePass==ONEPASS_MULTI ){
1083       assert( hasFK==0 && chngKey==0 );
1084       sqlite3VdbeChangeP5(v, OPFLAG_SAVEPOSITION);
1085     }
1086     if( !pParse->nested ){
1087       sqlite3VdbeAppendP4(v, pTab, P4_TABLE);
1088     }
1089 #else
1090     if( hasFK>1 || chngKey ){
1091       sqlite3VdbeAddOp2(v, OP_Delete, iDataCur, 0);
1092     }
1093 #endif
1094
1095     if( hasFK ){
1096       sqlite3FkCheck(pParse, pTab, 0, regNewRowid, aXRef, chngKey);
1097     }
1098
1099     /* Insert the new index entries and the new record. */
1100     sqlite3CompleteInsertion(
1101         pParse, pTab, iDataCur, iIdxCur, regNewRowid, aRegIdx,
1102         OPFLAG_ISUPDATE | (eOnePass==ONEPASS_MULTI ? OPFLAG_SAVEPOSITION : 0),
1103         0, 0
1104     );
1105
1106     /* Do any ON CASCADE, SET NULL or SET DEFAULT operations required to
1107     ** handle rows (possibly in other tables) that refer via a foreign key
1108     ** to the row just updated. */
1109     if( hasFK ){
1110       sqlite3FkActions(pParse, pTab, pChanges, regOldRowid, aXRef, chngKey);
1111     }
1112   }
1113
1114   /* Increment the row counter
1115   */
1116   if( regRowCount ){
1117     sqlite3VdbeAddOp2(v, OP_AddImm, regRowCount, 1);
1118   }
1119
1120   if( pTrigger ){
1121     sqlite3CodeRowTrigger(pParse, pTrigger, TK_UPDATE, pChanges,
1122         TRIGGER_AFTER, pTab, regOldRowid, onError, labelContinue);
1123   }
1124
1125   /* Repeat the above with the next record to be updated, until
1126   ** all record selected by the WHERE clause have been updated.
1127   */
1128   if( eOnePass==ONEPASS_SINGLE ){
1129     /* Nothing to do at end-of-loop for a single-pass */
1130   }else if( eOnePass==ONEPASS_MULTI ){
1131     sqlite3VdbeResolveLabel(v, labelContinue);
1132     sqlite3WhereEnd(pWInfo);
1133   }else{
1134     sqlite3VdbeResolveLabel(v, labelContinue);
1135     sqlite3VdbeAddOp2(v, OP_Next, iEph, addrTop); VdbeCoverage(v);
1136   }
1137   sqlite3VdbeResolveLabel(v, labelBreak);
1138
1139   /* Update the sqlite_sequence table by storing the content of the
1140   ** maximum rowid counter values recorded while inserting into
1141   ** autoincrement tables.
1142   */
1143   if( pParse->nested==0 && pParse->pTriggerTab==0 && pUpsert==0 ){
1144     sqlite3AutoincrementEnd(pParse);
1145   }
1146
1147   /*
1148   ** Return the number of rows that were changed, if we are tracking
1149   ** that information.
1150   */
1151   if( regRowCount ){
1152     sqlite3CodeChangeCount(v, regRowCount, "rows updated");
1153   }
1154
1155 update_cleanup:
1156   sqlite3AuthContextPop(&sContext);
1157   sqlite3DbFree(db, aXRef); /* Also frees aRegIdx[] and aToOpen[] */
1158   sqlite3SrcListDelete(db, pTabList);
1159   sqlite3ExprListDelete(db, pChanges);
1160   sqlite3ExprDelete(db, pWhere);
1161 #if defined(SQLITE_ENABLE_UPDATE_DELETE_LIMIT)
1162   sqlite3ExprListDelete(db, pOrderBy);
1163   sqlite3ExprDelete(db, pLimit);
1164 #endif
1165   return;
1166 }
1167 /* Make sure "isView" and other macros defined above are undefined. Otherwise
1168 ** they may interfere with compilation of other functions in this file
1169 ** (or in another file, if this file becomes part of the amalgamation).  */
1170 #ifdef isView
1171  #undef isView
1172 #endif
1173 #ifdef pTrigger
1174  #undef pTrigger
1175 #endif
1176
1177 #ifndef SQLITE_OMIT_VIRTUALTABLE
1178 /*
1179 ** Generate code for an UPDATE of a virtual table.
1180 **
1181 ** There are two possible strategies - the default and the special
1182 ** "onepass" strategy. Onepass is only used if the virtual table
1183 ** implementation indicates that pWhere may match at most one row.
1184 **
1185 ** The default strategy is to create an ephemeral table that contains
1186 ** for each row to be changed:
1187 **
1188 **   (A)  The original rowid of that row.
1189 **   (B)  The revised rowid for the row.
1190 **   (C)  The content of every column in the row.
1191 **
1192 ** Then loop through the contents of this ephemeral table executing a
1193 ** VUpdate for each row. When finished, drop the ephemeral table.
1194 **
1195 ** The "onepass" strategy does not use an ephemeral table. Instead, it
1196 ** stores the same values (A, B and C above) in a register array and
1197 ** makes a single invocation of VUpdate.
1198 */
1199 static void updateVirtualTable(
1200   Parse *pParse,       /* The parsing context */
1201   SrcList *pSrc,       /* The virtual table to be modified */
1202   Table *pTab,         /* The virtual table */
1203   ExprList *pChanges,  /* The columns to change in the UPDATE statement */
1204   Expr *pRowid,        /* Expression used to recompute the rowid */
1205   int *aXRef,          /* Mapping from columns of pTab to entries in pChanges */
1206   Expr *pWhere,        /* WHERE clause of the UPDATE statement */
1207   int onError          /* ON CONFLICT strategy */
1208 ){
1209   Vdbe *v = pParse->pVdbe;  /* Virtual machine under construction */
1210   int ephemTab;             /* Table holding the result of the SELECT */
1211   int i;                    /* Loop counter */
1212   sqlite3 *db = pParse->db; /* Database connection */
1213   const char *pVTab = (const char*)sqlite3GetVTable(db, pTab);
1214   WhereInfo *pWInfo = 0;
1215   int nArg = 2 + pTab->nCol;      /* Number of arguments to VUpdate */
1216   int regArg;                     /* First register in VUpdate arg array */
1217   int regRec;                     /* Register in which to assemble record */
1218   int regRowid;                   /* Register for ephemeral table rowid */
1219   int iCsr = pSrc->a[0].iCursor;  /* Cursor used for virtual table scan */
1220   int aDummy[2];                  /* Unused arg for sqlite3WhereOkOnePass() */
1221   int eOnePass;                   /* True to use onepass strategy */
1222   int addr;                       /* Address of OP_OpenEphemeral */
1223
1224   /* Allocate nArg registers in which to gather the arguments for VUpdate. Then
1225   ** create and open the ephemeral table in which the records created from
1226   ** these arguments will be temporarily stored. */
1227   assert( v );
1228   ephemTab = pParse->nTab++;
1229   addr= sqlite3VdbeAddOp2(v, OP_OpenEphemeral, ephemTab, nArg);
1230   regArg = pParse->nMem + 1;
1231   pParse->nMem += nArg;
1232   if( pSrc->nSrc>1 ){
1233     Index *pPk = 0;
1234     Expr *pRow;
1235     ExprList *pList;
1236     if( HasRowid(pTab) ){
1237       if( pRowid ){
1238         pRow = sqlite3ExprDup(db, pRowid, 0);
1239       }else{
1240         pRow = sqlite3PExpr(pParse, TK_ROW, 0, 0);
1241       }
1242     }else{
1243       i16 iPk;      /* PRIMARY KEY column */
1244       pPk = sqlite3PrimaryKeyIndex(pTab);
1245       assert( pPk!=0 );
1246       assert( pPk->nKeyCol==1 );
1247       iPk = pPk->aiColumn[0];
1248       if( aXRef[iPk]>=0 ){
1249         pRow = sqlite3ExprDup(db, pChanges->a[aXRef[iPk]].pExpr, 0);
1250       }else{
1251         pRow = exprRowColumn(pParse, iPk);
1252       }
1253     }
1254     pList = sqlite3ExprListAppend(pParse, 0, pRow);
1255
1256     for(i=0; i<pTab->nCol; i++){
1257       if( aXRef[i]>=0 ){
1258         pList = sqlite3ExprListAppend(pParse, pList,
1259           sqlite3ExprDup(db, pChanges->a[aXRef[i]].pExpr, 0)
1260         );
1261       }else{
1262         Expr *pRowExpr = exprRowColumn(pParse, i);
1263         if( pRowExpr ) pRowExpr->op2 = OPFLAG_NOCHNG;
1264         pList = sqlite3ExprListAppend(pParse, pList, pRowExpr);
1265       }
1266     }
1267
1268     updateFromSelect(pParse, ephemTab, pPk, pList, pSrc, pWhere, 0, 0);
1269     sqlite3ExprListDelete(db, pList);
1270     eOnePass = ONEPASS_OFF;
1271   }else{
1272     regRec = ++pParse->nMem;
1273     regRowid = ++pParse->nMem;
1274
1275     /* Start scanning the virtual table */
1276     pWInfo = sqlite3WhereBegin(
1277         pParse, pSrc, pWhere, 0, 0, 0, WHERE_ONEPASS_DESIRED, 0
1278     );
1279     if( pWInfo==0 ) return;
1280
1281     /* Populate the argument registers. */
1282     for(i=0; i<pTab->nCol; i++){
1283       assert( (pTab->aCol[i].colFlags & COLFLAG_GENERATED)==0 );
1284       if( aXRef[i]>=0 ){
1285         sqlite3ExprCode(pParse, pChanges->a[aXRef[i]].pExpr, regArg+2+i);
1286       }else{
1287         sqlite3VdbeAddOp3(v, OP_VColumn, iCsr, i, regArg+2+i);
1288         sqlite3VdbeChangeP5(v, OPFLAG_NOCHNG);/* For sqlite3_vtab_nochange() */
1289       }
1290     }
1291     if( HasRowid(pTab) ){
1292       sqlite3VdbeAddOp2(v, OP_Rowid, iCsr, regArg);
1293       if( pRowid ){
1294         sqlite3ExprCode(pParse, pRowid, regArg+1);
1295       }else{
1296         sqlite3VdbeAddOp2(v, OP_Rowid, iCsr, regArg+1);
1297       }
1298     }else{
1299       Index *pPk;   /* PRIMARY KEY index */
1300       i16 iPk;      /* PRIMARY KEY column */
1301       pPk = sqlite3PrimaryKeyIndex(pTab);
1302       assert( pPk!=0 );
1303       assert( pPk->nKeyCol==1 );
1304       iPk = pPk->aiColumn[0];
1305       sqlite3VdbeAddOp3(v, OP_VColumn, iCsr, iPk, regArg);
1306       sqlite3VdbeAddOp2(v, OP_SCopy, regArg+2+iPk, regArg+1);
1307     }
1308
1309     eOnePass = sqlite3WhereOkOnePass(pWInfo, aDummy);
1310
1311     /* There is no ONEPASS_MULTI on virtual tables */
1312     assert( eOnePass==ONEPASS_OFF || eOnePass==ONEPASS_SINGLE );
1313
1314     if( eOnePass ){
1315       /* If using the onepass strategy, no-op out the OP_OpenEphemeral coded
1316       ** above. */
1317       sqlite3VdbeChangeToNoop(v, addr);
1318       sqlite3VdbeAddOp1(v, OP_Close, iCsr);
1319     }else{
1320       /* Create a record from the argument register contents and insert it into
1321       ** the ephemeral table. */
1322       sqlite3MultiWrite(pParse);
1323       sqlite3VdbeAddOp3(v, OP_MakeRecord, regArg, nArg, regRec);
1324 #if defined(SQLITE_DEBUG) && !defined(SQLITE_ENABLE_NULL_TRIM)
1325       /* Signal an assert() within OP_MakeRecord that it is allowed to
1326       ** accept no-change records with serial_type 10 */
1327       sqlite3VdbeChangeP5(v, OPFLAG_NOCHNG_MAGIC);
1328 #endif
1329       sqlite3VdbeAddOp2(v, OP_NewRowid, ephemTab, regRowid);
1330       sqlite3VdbeAddOp3(v, OP_Insert, ephemTab, regRec, regRowid);
1331     }
1332   }
1333
1334
1335   if( eOnePass==ONEPASS_OFF ){
1336     /* End the virtual table scan */
1337     if( pSrc->nSrc==1 ){
1338       sqlite3WhereEnd(pWInfo);
1339     }
1340
1341     /* Begin scanning through the ephemeral table. */
1342     addr = sqlite3VdbeAddOp1(v, OP_Rewind, ephemTab); VdbeCoverage(v);
1343
1344     /* Extract arguments from the current row of the ephemeral table and
1345     ** invoke the VUpdate method.  */
1346     for(i=0; i<nArg; i++){
1347       sqlite3VdbeAddOp3(v, OP_Column, ephemTab, i, regArg+i);
1348     }
1349   }
1350   sqlite3VtabMakeWritable(pParse, pTab);
1351   sqlite3VdbeAddOp4(v, OP_VUpdate, 0, nArg, regArg, pVTab, P4_VTAB);
1352   sqlite3VdbeChangeP5(v, onError==OE_Default ? OE_Abort : onError);
1353   sqlite3MayAbort(pParse);
1354
1355   /* End of the ephemeral table scan. Or, if using the onepass strategy,
1356   ** jump to here if the scan visited zero rows. */
1357   if( eOnePass==ONEPASS_OFF ){
1358     sqlite3VdbeAddOp2(v, OP_Next, ephemTab, addr+1); VdbeCoverage(v);
1359     sqlite3VdbeJumpHere(v, addr);
1360     sqlite3VdbeAddOp2(v, OP_Close, ephemTab, 0);
1361   }else{
1362     sqlite3WhereEnd(pWInfo);
1363   }
1364 }
1365 #endif /* SQLITE_OMIT_VIRTUALTABLE */