xref: /sqlite-3.40.0/src/update.c (revision cd7274ce)
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 ** $Id: update.c,v 1.141 2007/11/11 18:36:34 drh Exp $
16 */
17 #include "sqliteInt.h"
18 
19 #ifndef SQLITE_OMIT_VIRTUALTABLE
20 /* Forward declaration */
21 static void updateVirtualTable(
22   Parse *pParse,       /* The parsing context */
23   SrcList *pSrc,       /* The virtual table to be modified */
24   Table *pTab,         /* The virtual table */
25   ExprList *pChanges,  /* The columns to change in the UPDATE statement */
26   Expr *pRowidExpr,    /* Expression used to recompute the rowid */
27   int *aXRef,          /* Mapping from columns of pTab to entries in pChanges */
28   Expr *pWhere         /* WHERE clause of the UPDATE statement */
29 );
30 #endif /* SQLITE_OMIT_VIRTUALTABLE */
31 
32 /*
33 ** The most recently coded instruction was an OP_Column to retrieve the
34 ** i-th column of table pTab. This routine sets the P3 parameter of the
35 ** OP_Column to the default value, if any.
36 **
37 ** The default value of a column is specified by a DEFAULT clause in the
38 ** column definition. This was either supplied by the user when the table
39 ** was created, or added later to the table definition by an ALTER TABLE
40 ** command. If the latter, then the row-records in the table btree on disk
41 ** may not contain a value for the column and the default value, taken
42 ** from the P3 parameter of the OP_Column instruction, is returned instead.
43 ** If the former, then all row-records are guaranteed to include a value
44 ** for the column and the P3 value is not required.
45 **
46 ** Column definitions created by an ALTER TABLE command may only have
47 ** literal default values specified: a number, null or a string. (If a more
48 ** complicated default expression value was provided, it is evaluated
49 ** when the ALTER TABLE is executed and one of the literal values written
50 ** into the sqlite_master table.)
51 **
52 ** Therefore, the P3 parameter is only required if the default value for
53 ** the column is a literal number, string or null. The sqlite3ValueFromExpr()
54 ** function is capable of transforming these types of expressions into
55 ** sqlite3_value objects.
56 */
57 void sqlite3ColumnDefault(Vdbe *v, Table *pTab, int i){
58   if( pTab && !pTab->pSelect ){
59     sqlite3_value *pValue;
60     u8 enc = ENC(sqlite3VdbeDb(v));
61     Column *pCol = &pTab->aCol[i];
62     assert( i<pTab->nCol );
63     sqlite3ValueFromExpr(sqlite3VdbeDb(v), pCol->pDflt, enc, pCol->affinity, &pValue);
64     if( pValue ){
65       sqlite3VdbeChangeP3(v, -1, (const char *)pValue, P3_MEM);
66     }else{
67       VdbeComment((v, "# %s.%s", pTab->zName, pCol->zName));
68     }
69   }
70 }
71 
72 /*
73 ** Process an UPDATE statement.
74 **
75 **   UPDATE OR IGNORE table_wxyz SET a=b, c=d WHERE e<5 AND f NOT NULL;
76 **          \_______/ \________/     \______/       \________________/
77 *            onError   pTabList      pChanges             pWhere
78 */
79 void sqlite3Update(
80   Parse *pParse,         /* The parser context */
81   SrcList *pTabList,     /* The table in which we should change things */
82   ExprList *pChanges,    /* Things to be changed */
83   Expr *pWhere,          /* The WHERE clause.  May be null */
84   int onError            /* How to handle constraint errors */
85 ){
86   int i, j;              /* Loop counters */
87   Table *pTab;           /* The table to be updated */
88   int addr = 0;          /* VDBE instruction address of the start of the loop */
89   WhereInfo *pWInfo;     /* Information about the WHERE clause */
90   Vdbe *v;               /* The virtual database engine */
91   Index *pIdx;           /* For looping over indices */
92   int nIdx;              /* Number of indices that need updating */
93   int nIdxTotal;         /* Total number of indices */
94   int iCur;              /* VDBE Cursor number of pTab */
95   sqlite3 *db;           /* The database structure */
96   Index **apIdx = 0;     /* An array of indices that need updating too */
97   char *aIdxUsed = 0;    /* aIdxUsed[i]==1 if the i-th index is used */
98   int *aXRef = 0;        /* aXRef[i] is the index in pChanges->a[] of the
99                          ** an expression for the i-th column of the table.
100                          ** aXRef[i]==-1 if the i-th column is not changed. */
101   int chngRowid;         /* True if the record number is being changed */
102   Expr *pRowidExpr = 0;  /* Expression defining the new record number */
103   int openAll = 0;       /* True if all indices need to be opened */
104   AuthContext sContext;  /* The authorization context */
105   NameContext sNC;       /* The name-context to resolve expressions in */
106   int iDb;               /* Database containing the table being updated */
107   int memCnt = 0;        /* Memory cell used for counting rows changed */
108 
109 #ifndef SQLITE_OMIT_TRIGGER
110   int isView;                  /* Trying to update a view */
111   int triggers_exist = 0;      /* True if any row triggers exist */
112 #endif
113 
114   int newIdx      = -1;  /* index of trigger "new" temp table       */
115   int oldIdx      = -1;  /* index of trigger "old" temp table       */
116 
117   sContext.pParse = 0;
118   db = pParse->db;
119   if( pParse->nErr || db->mallocFailed ){
120     goto update_cleanup;
121   }
122   assert( pTabList->nSrc==1 );
123 
124   /* Locate the table which we want to update.
125   */
126   pTab = sqlite3SrcListLookup(pParse, pTabList);
127   if( pTab==0 ) goto update_cleanup;
128   iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
129 
130   /* Figure out if we have any triggers and if the table being
131   ** updated is a view
132   */
133 #ifndef SQLITE_OMIT_TRIGGER
134   triggers_exist = sqlite3TriggersExist(pParse, pTab, TK_UPDATE, pChanges);
135   isView = pTab->pSelect!=0;
136 #else
137 # define triggers_exist 0
138 # define isView 0
139 #endif
140 #ifdef SQLITE_OMIT_VIEW
141 # undef isView
142 # define isView 0
143 #endif
144 
145   if( sqlite3IsReadOnly(pParse, pTab, triggers_exist) ){
146     goto update_cleanup;
147   }
148   if( sqlite3ViewGetColumnNames(pParse, pTab) ){
149     goto update_cleanup;
150   }
151   aXRef = sqlite3DbMallocRaw(db, sizeof(int) * pTab->nCol );
152   if( aXRef==0 ) goto update_cleanup;
153   for(i=0; i<pTab->nCol; i++) aXRef[i] = -1;
154 
155   /* If there are FOR EACH ROW triggers, allocate cursors for the
156   ** special OLD and NEW tables
157   */
158   if( triggers_exist ){
159     newIdx = pParse->nTab++;
160     oldIdx = pParse->nTab++;
161   }
162 
163   /* Allocate a cursors for the main database table and for all indices.
164   ** The index cursors might not be used, but if they are used they
165   ** need to occur right after the database cursor.  So go ahead and
166   ** allocate enough space, just in case.
167   */
168   pTabList->a[0].iCursor = iCur = pParse->nTab++;
169   for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
170     pParse->nTab++;
171   }
172 
173   /* Initialize the name-context */
174   memset(&sNC, 0, sizeof(sNC));
175   sNC.pParse = pParse;
176   sNC.pSrcList = pTabList;
177 
178   /* Resolve the column names in all the expressions of the
179   ** of the UPDATE statement.  Also find the column index
180   ** for each column to be updated in the pChanges array.  For each
181   ** column to be updated, make sure we have authorization to change
182   ** that column.
183   */
184   chngRowid = 0;
185   for(i=0; i<pChanges->nExpr; i++){
186     if( sqlite3ExprResolveNames(&sNC, pChanges->a[i].pExpr) ){
187       goto update_cleanup;
188     }
189     for(j=0; j<pTab->nCol; j++){
190       if( sqlite3StrICmp(pTab->aCol[j].zName, pChanges->a[i].zName)==0 ){
191         if( j==pTab->iPKey ){
192           chngRowid = 1;
193           pRowidExpr = pChanges->a[i].pExpr;
194         }
195         aXRef[j] = i;
196         break;
197       }
198     }
199     if( j>=pTab->nCol ){
200       if( sqlite3IsRowid(pChanges->a[i].zName) ){
201         chngRowid = 1;
202         pRowidExpr = pChanges->a[i].pExpr;
203       }else{
204         sqlite3ErrorMsg(pParse, "no such column: %s", pChanges->a[i].zName);
205         goto update_cleanup;
206       }
207     }
208 #ifndef SQLITE_OMIT_AUTHORIZATION
209     {
210       int rc;
211       rc = sqlite3AuthCheck(pParse, SQLITE_UPDATE, pTab->zName,
212                            pTab->aCol[j].zName, db->aDb[iDb].zName);
213       if( rc==SQLITE_DENY ){
214         goto update_cleanup;
215       }else if( rc==SQLITE_IGNORE ){
216         aXRef[j] = -1;
217       }
218     }
219 #endif
220   }
221 
222   /* Allocate memory for the array apIdx[] and fill it with pointers to every
223   ** index that needs to be updated.  Indices only need updating if their
224   ** key includes one of the columns named in pChanges or if the record
225   ** number of the original table entry is changing.
226   */
227   for(nIdx=nIdxTotal=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, nIdxTotal++){
228     if( chngRowid ){
229       i = 0;
230     }else {
231       for(i=0; i<pIdx->nColumn; i++){
232         if( aXRef[pIdx->aiColumn[i]]>=0 ) break;
233       }
234     }
235     if( i<pIdx->nColumn ) nIdx++;
236   }
237   if( nIdxTotal>0 ){
238     apIdx = sqlite3DbMallocRaw(db, sizeof(Index*) * nIdx + nIdxTotal );
239     if( apIdx==0 ) goto update_cleanup;
240     aIdxUsed = (char*)&apIdx[nIdx];
241   }
242   for(nIdx=j=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, j++){
243     if( chngRowid ){
244       i = 0;
245     }else{
246       for(i=0; i<pIdx->nColumn; i++){
247         if( aXRef[pIdx->aiColumn[i]]>=0 ) break;
248       }
249     }
250     if( i<pIdx->nColumn ){
251       apIdx[nIdx++] = pIdx;
252       aIdxUsed[j] = 1;
253     }else{
254       aIdxUsed[j] = 0;
255     }
256   }
257 
258   /* Begin generating code.
259   */
260   v = sqlite3GetVdbe(pParse);
261   if( v==0 ) goto update_cleanup;
262   if( pParse->nested==0 ) sqlite3VdbeCountChanges(v);
263   sqlite3BeginWriteOperation(pParse, 1, iDb);
264 
265 #ifndef SQLITE_OMIT_VIRTUALTABLE
266   /* Virtual tables must be handled separately */
267   if( IsVirtual(pTab) ){
268     updateVirtualTable(pParse, pTabList, pTab, pChanges, pRowidExpr, aXRef,
269                        pWhere);
270     pWhere = 0;
271     pTabList = 0;
272     goto update_cleanup;
273   }
274 #endif
275 
276   /* Resolve the column names in all the expressions in the
277   ** WHERE clause.
278   */
279   if( sqlite3ExprResolveNames(&sNC, pWhere) ){
280     goto update_cleanup;
281   }
282 
283   /* Start the view context
284   */
285   if( isView ){
286     sqlite3AuthContextPush(pParse, &sContext, pTab->zName);
287   }
288 
289   /* If we are trying to update a view, realize that view into
290   ** a ephemeral table.
291   */
292   if( isView ){
293     Select *pView;
294     pView = sqlite3SelectDup(db, pTab->pSelect);
295     sqlite3Select(pParse, pView, SRT_EphemTab, iCur, 0, 0, 0, 0);
296     sqlite3SelectDelete(pView);
297   }
298 
299   /* Begin the database scan
300   */
301   pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, 0);
302   if( pWInfo==0 ) goto update_cleanup;
303 
304   /* Remember the rowid of every item to be updated.
305   */
306   sqlite3VdbeAddOp(v, IsVirtual(pTab) ? OP_VRowid : OP_Rowid, iCur, 0);
307   sqlite3VdbeAddOp(v, OP_FifoWrite, 0, 0);
308 
309   /* End the database scan loop.
310   */
311   sqlite3WhereEnd(pWInfo);
312 
313   /* Initialize the count of updated rows
314   */
315   if( db->flags & SQLITE_CountRows && !pParse->trigStack ){
316     memCnt = pParse->nMem++;
317     sqlite3VdbeAddOp(v, OP_MemInt, 0, memCnt);
318   }
319 
320   if( triggers_exist ){
321     int mem1;      /* Memory address storing the rowid for next row to update */
322 
323     /* Create pseudo-tables for NEW and OLD
324     */
325     sqlite3VdbeAddOp(v, OP_OpenPseudo, oldIdx, 0);
326     sqlite3VdbeAddOp(v, OP_SetNumColumns, oldIdx, pTab->nCol);
327     sqlite3VdbeAddOp(v, OP_OpenPseudo, newIdx, 0);
328     sqlite3VdbeAddOp(v, OP_SetNumColumns, newIdx, pTab->nCol);
329 
330     /* The top of the update loop for when there are triggers.
331     */
332     addr = sqlite3VdbeAddOp(v, OP_FifoRead, 0, 0);
333     mem1 = pParse->nMem++;
334     sqlite3VdbeAddOp(v, OP_MemStore, mem1, 0);
335 
336     if( !isView ){
337       /* Open a cursor and make it point to the record that is
338       ** being updated.
339       */
340       sqlite3OpenTable(pParse, iCur, iDb, pTab, OP_OpenRead);
341     }
342     sqlite3VdbeAddOp(v, OP_MoveGe, iCur, 0);
343 
344     /* Generate the OLD table
345     */
346     sqlite3VdbeAddOp(v, OP_Rowid, iCur, 0);
347     sqlite3VdbeAddOp(v, OP_RowData, iCur, 0);
348     sqlite3VdbeAddOp(v, OP_Insert, oldIdx, 0);
349 
350     /* Generate the NEW table
351     */
352     if( chngRowid ){
353       sqlite3ExprCodeAndCache(pParse, pRowidExpr);
354     }else{
355       sqlite3VdbeAddOp(v, OP_Rowid, iCur, 0);
356     }
357     for(i=0; i<pTab->nCol; i++){
358       if( i==pTab->iPKey ){
359         sqlite3VdbeAddOp(v, OP_Null, 0, 0);
360         continue;
361       }
362       j = aXRef[i];
363       if( j<0 ){
364         sqlite3VdbeAddOp(v, OP_Column, iCur, i);
365         sqlite3ColumnDefault(v, pTab, i);
366       }else{
367         sqlite3ExprCodeAndCache(pParse, pChanges->a[j].pExpr);
368       }
369     }
370     sqlite3VdbeAddOp(v, OP_MakeRecord, pTab->nCol, 0);
371     if( !isView ){
372       sqlite3TableAffinityStr(v, pTab);
373     }
374     if( pParse->nErr ) goto update_cleanup;
375     sqlite3VdbeAddOp(v, OP_Insert, newIdx, 0);
376     if( !isView ){
377       sqlite3VdbeAddOp(v, OP_Close, iCur, 0);
378     }
379 
380     /* Fire the BEFORE and INSTEAD OF triggers
381     */
382     if( sqlite3CodeRowTrigger(pParse, TK_UPDATE, pChanges, TRIGGER_BEFORE, pTab,
383           newIdx, oldIdx, onError, addr) ){
384       goto update_cleanup;
385     }
386 
387     if( !isView ){
388       sqlite3VdbeAddOp(v, OP_MemLoad, mem1, 0);
389       sqlite3VdbeAddOp(v, OP_Dup, 0, 0);
390     }
391   }
392 
393   if( !isView && !IsVirtual(pTab) ){
394     /*
395     ** Open every index that needs updating.  Note that if any
396     ** index could potentially invoke a REPLACE conflict resolution
397     ** action, then we need to open all indices because we might need
398     ** to be deleting some records.
399     */
400     sqlite3OpenTable(pParse, iCur, iDb, pTab, OP_OpenWrite);
401     if( onError==OE_Replace ){
402       openAll = 1;
403     }else{
404       openAll = 0;
405       for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
406         if( pIdx->onError==OE_Replace ){
407           openAll = 1;
408           break;
409         }
410       }
411     }
412     for(i=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, i++){
413       if( openAll || aIdxUsed[i] ){
414         KeyInfo *pKey = sqlite3IndexKeyinfo(pParse, pIdx);
415         sqlite3VdbeAddOp(v, OP_Integer, iDb, 0);
416         sqlite3VdbeOp3(v, OP_OpenWrite, iCur+i+1, pIdx->tnum,
417                        (char*)pKey, P3_KEYINFO_HANDOFF);
418         assert( pParse->nTab>iCur+i+1 );
419       }
420     }
421 
422     /* Loop over every record that needs updating.  We have to load
423     ** the old data for each record to be updated because some columns
424     ** might not change and we will need to copy the old value.
425     ** Also, the old data is needed to delete the old index entries.
426     ** So make the cursor point at the old record.
427     */
428     if( !triggers_exist ){
429       addr = sqlite3VdbeAddOp(v, OP_FifoRead, 0, 0);
430       sqlite3VdbeAddOp(v, OP_Dup, 0, 0);
431     }
432     sqlite3VdbeAddOp(v, OP_NotExists, iCur, addr);
433 
434     /* If the record number will change, push the record number as it
435     ** will be after the update. (The old record number is currently
436     ** on top of the stack.)
437     */
438     if( chngRowid ){
439       sqlite3ExprCode(pParse, pRowidExpr);
440       sqlite3VdbeAddOp(v, OP_MustBeInt, 0, 0);
441     }
442 
443     /* Compute new data for this record.
444     */
445     for(i=0; i<pTab->nCol; i++){
446       if( i==pTab->iPKey ){
447         sqlite3VdbeAddOp(v, OP_Null, 0, 0);
448         continue;
449       }
450       j = aXRef[i];
451       if( j<0 ){
452         sqlite3VdbeAddOp(v, OP_Column, iCur, i);
453         sqlite3ColumnDefault(v, pTab, i);
454       }else{
455         sqlite3ExprCode(pParse, pChanges->a[j].pExpr);
456       }
457     }
458 
459     /* Do constraint checks
460     */
461     sqlite3GenerateConstraintChecks(pParse, pTab, iCur, aIdxUsed, chngRowid, 1,
462                                    onError, addr);
463 
464     /* Delete the old indices for the current record.
465     */
466     sqlite3GenerateRowIndexDelete(v, pTab, iCur, aIdxUsed);
467 
468     /* If changing the record number, delete the old record.
469     */
470     if( chngRowid ){
471       sqlite3VdbeAddOp(v, OP_Delete, iCur, 0);
472     }
473 
474     /* Create the new index entries and the new record.
475     */
476     sqlite3CompleteInsertion(pParse, pTab, iCur, aIdxUsed, chngRowid, 1, -1, 0);
477   }
478 
479   /* Increment the row counter
480   */
481   if( db->flags & SQLITE_CountRows && !pParse->trigStack){
482     sqlite3VdbeAddOp(v, OP_MemIncr, 1, memCnt);
483   }
484 
485   /* If there are triggers, close all the cursors after each iteration
486   ** through the loop.  The fire the after triggers.
487   */
488   if( triggers_exist ){
489     if( !isView ){
490       for(i=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, i++){
491         if( openAll || aIdxUsed[i] )
492           sqlite3VdbeAddOp(v, OP_Close, iCur+i+1, 0);
493       }
494       sqlite3VdbeAddOp(v, OP_Close, iCur, 0);
495     }
496     if( sqlite3CodeRowTrigger(pParse, TK_UPDATE, pChanges, TRIGGER_AFTER, pTab,
497           newIdx, oldIdx, onError, addr) ){
498       goto update_cleanup;
499     }
500   }
501 
502   /* Repeat the above with the next record to be updated, until
503   ** all record selected by the WHERE clause have been updated.
504   */
505   sqlite3VdbeAddOp(v, OP_Goto, 0, addr);
506   sqlite3VdbeJumpHere(v, addr);
507 
508   /* Close all tables if there were no FOR EACH ROW triggers */
509   if( !triggers_exist ){
510     for(i=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, i++){
511       if( openAll || aIdxUsed[i] ){
512         sqlite3VdbeAddOp(v, OP_Close, iCur+i+1, 0);
513       }
514     }
515     sqlite3VdbeAddOp(v, OP_Close, iCur, 0);
516   }else{
517     sqlite3VdbeAddOp(v, OP_Close, newIdx, 0);
518     sqlite3VdbeAddOp(v, OP_Close, oldIdx, 0);
519   }
520 
521   /*
522   ** Return the number of rows that were changed. If this routine is
523   ** generating code because of a call to sqlite3NestedParse(), do not
524   ** invoke the callback function.
525   */
526   if( db->flags & SQLITE_CountRows && !pParse->trigStack && pParse->nested==0 ){
527     sqlite3VdbeAddOp(v, OP_MemLoad, memCnt, 0);
528     sqlite3VdbeAddOp(v, OP_Callback, 1, 0);
529     sqlite3VdbeSetNumCols(v, 1);
530     sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "rows updated", P3_STATIC);
531   }
532 
533 update_cleanup:
534   sqlite3AuthContextPop(&sContext);
535   sqlite3_free(apIdx);
536   sqlite3_free(aXRef);
537   sqlite3SrcListDelete(pTabList);
538   sqlite3ExprListDelete(pChanges);
539   sqlite3ExprDelete(pWhere);
540   return;
541 }
542 
543 #ifndef SQLITE_OMIT_VIRTUALTABLE
544 /*
545 ** Generate code for an UPDATE of a virtual table.
546 **
547 ** The strategy is that we create an ephemerial table that contains
548 ** for each row to be changed:
549 **
550 **   (A)  The original rowid of that row.
551 **   (B)  The revised rowid for the row. (note1)
552 **   (C)  The content of every column in the row.
553 **
554 ** Then we loop over this ephemeral table and for each row in
555 ** the ephermeral table call VUpdate.
556 **
557 ** When finished, drop the ephemeral table.
558 **
559 ** (note1) Actually, if we know in advance that (A) is always the same
560 ** as (B) we only store (A), then duplicate (A) when pulling
561 ** it out of the ephemeral table before calling VUpdate.
562 */
563 static void updateVirtualTable(
564   Parse *pParse,       /* The parsing context */
565   SrcList *pSrc,       /* The virtual table to be modified */
566   Table *pTab,         /* The virtual table */
567   ExprList *pChanges,  /* The columns to change in the UPDATE statement */
568   Expr *pRowid,        /* Expression used to recompute the rowid */
569   int *aXRef,          /* Mapping from columns of pTab to entries in pChanges */
570   Expr *pWhere         /* WHERE clause of the UPDATE statement */
571 ){
572   Vdbe *v = pParse->pVdbe;  /* Virtual machine under construction */
573   ExprList *pEList = 0;     /* The result set of the SELECT statement */
574   Select *pSelect = 0;      /* The SELECT statement */
575   Expr *pExpr;              /* Temporary expression */
576   int ephemTab;             /* Table holding the result of the SELECT */
577   int i;                    /* Loop counter */
578   int addr;                 /* Address of top of loop */
579   sqlite3 *db = pParse->db; /* Database connection */
580 
581   /* Construct the SELECT statement that will find the new values for
582   ** all updated rows.
583   */
584   pEList = sqlite3ExprListAppend(pParse, 0,
585                                  sqlite3CreateIdExpr(pParse, "_rowid_"), 0);
586   if( pRowid ){
587     pEList = sqlite3ExprListAppend(pParse, pEList,
588                                    sqlite3ExprDup(db, pRowid), 0);
589   }
590   assert( pTab->iPKey<0 );
591   for(i=0; i<pTab->nCol; i++){
592     if( aXRef[i]>=0 ){
593       pExpr = sqlite3ExprDup(db, pChanges->a[aXRef[i]].pExpr);
594     }else{
595       pExpr = sqlite3CreateIdExpr(pParse, pTab->aCol[i].zName);
596     }
597     pEList = sqlite3ExprListAppend(pParse, pEList, pExpr, 0);
598   }
599   pSelect = sqlite3SelectNew(pParse, pEList, pSrc, pWhere, 0, 0, 0, 0, 0, 0);
600 
601   /* Create the ephemeral table into which the update results will
602   ** be stored.
603   */
604   assert( v );
605   ephemTab = pParse->nTab++;
606   sqlite3VdbeAddOp(v, OP_OpenEphemeral, ephemTab, pTab->nCol+1+(pRowid!=0));
607 
608   /* fill the ephemeral table
609   */
610   sqlite3Select(pParse, pSelect, SRT_Table, ephemTab, 0, 0, 0, 0);
611 
612   /*
613   ** Generate code to scan the ephemeral table and call VDelete and
614   ** VInsert
615   */
616   sqlite3VdbeAddOp(v, OP_Rewind, ephemTab, 0);
617   addr = sqlite3VdbeCurrentAddr(v);
618   sqlite3VdbeAddOp(v, OP_Column,  ephemTab, 0);
619   if( pRowid ){
620     sqlite3VdbeAddOp(v, OP_Column, ephemTab, 1);
621   }else{
622     sqlite3VdbeAddOp(v, OP_Dup, 0, 0);
623   }
624   for(i=0; i<pTab->nCol; i++){
625     sqlite3VdbeAddOp(v, OP_Column, ephemTab, i+1+(pRowid!=0));
626   }
627   pParse->pVirtualLock = pTab;
628   sqlite3VdbeOp3(v, OP_VUpdate, 0, pTab->nCol+2,
629                      (const char*)pTab->pVtab, P3_VTAB);
630   sqlite3VdbeAddOp(v, OP_Next, ephemTab, addr);
631   sqlite3VdbeJumpHere(v, addr-1);
632   sqlite3VdbeAddOp(v, OP_Close, ephemTab, 0);
633 
634   /* Cleanup */
635   sqlite3SelectDelete(pSelect);
636 }
637 #endif /* SQLITE_OMIT_VIRTUALTABLE */
638