xref: /sqlite-3.40.0/src/update.c (revision 85b623f2)
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 1.144 2007/12/12 16:06:23 danielk1977 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   int mem1;      /* Memory address storing the rowid for next row to update */
109 
110 #ifndef SQLITE_OMIT_TRIGGER
111   int isView;                  /* Trying to update a view */
112   int triggers_exist = 0;      /* True if any row triggers exist */
113 #endif
114 
115   int newIdx      = -1;  /* index of trigger "new" temp table       */
116   int oldIdx      = -1;  /* index of trigger "old" temp table       */
117 
118   sContext.pParse = 0;
119   db = pParse->db;
120   if( pParse->nErr || db->mallocFailed ){
121     goto update_cleanup;
122   }
123   assert( pTabList->nSrc==1 );
124 
125   /* Locate the table which we want to update.
126   */
127   pTab = sqlite3SrcListLookup(pParse, pTabList);
128   if( pTab==0 ) goto update_cleanup;
129   iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
130 
131   /* Figure out if we have any triggers and if the table being
132   ** updated is a view
133   */
134 #ifndef SQLITE_OMIT_TRIGGER
135   triggers_exist = sqlite3TriggersExist(pParse, pTab, TK_UPDATE, pChanges);
136   isView = pTab->pSelect!=0;
137 #else
138 # define triggers_exist 0
139 # define isView 0
140 #endif
141 #ifdef SQLITE_OMIT_VIEW
142 # undef isView
143 # define isView 0
144 #endif
145 
146   if( sqlite3IsReadOnly(pParse, pTab, triggers_exist) ){
147     goto update_cleanup;
148   }
149   if( sqlite3ViewGetColumnNames(pParse, pTab) ){
150     goto update_cleanup;
151   }
152   aXRef = sqlite3DbMallocRaw(db, sizeof(int) * pTab->nCol );
153   if( aXRef==0 ) goto update_cleanup;
154   for(i=0; i<pTab->nCol; i++) aXRef[i] = -1;
155 
156   /* If there are FOR EACH ROW triggers, allocate cursors for the
157   ** special OLD and NEW tables
158   */
159   if( triggers_exist ){
160     newIdx = pParse->nTab++;
161     oldIdx = pParse->nTab++;
162   }
163 
164   /* Allocate a cursors for the main database table and for all indices.
165   ** The index cursors might not be used, but if they are used they
166   ** need to occur right after the database cursor.  So go ahead and
167   ** allocate enough space, just in case.
168   */
169   pTabList->a[0].iCursor = iCur = pParse->nTab++;
170   for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
171     pParse->nTab++;
172   }
173 
174   /* Initialize the name-context */
175   memset(&sNC, 0, sizeof(sNC));
176   sNC.pParse = pParse;
177   sNC.pSrcList = pTabList;
178 
179   /* Resolve the column names in all the expressions of the
180   ** of the UPDATE statement.  Also find the column index
181   ** for each column to be updated in the pChanges array.  For each
182   ** column to be updated, make sure we have authorization to change
183   ** that column.
184   */
185   chngRowid = 0;
186   for(i=0; i<pChanges->nExpr; i++){
187     if( sqlite3ExprResolveNames(&sNC, pChanges->a[i].pExpr) ){
188       goto update_cleanup;
189     }
190     for(j=0; j<pTab->nCol; j++){
191       if( sqlite3StrICmp(pTab->aCol[j].zName, pChanges->a[i].zName)==0 ){
192         if( j==pTab->iPKey ){
193           chngRowid = 1;
194           pRowidExpr = pChanges->a[i].pExpr;
195         }
196         aXRef[j] = i;
197         break;
198       }
199     }
200     if( j>=pTab->nCol ){
201       if( sqlite3IsRowid(pChanges->a[i].zName) ){
202         chngRowid = 1;
203         pRowidExpr = pChanges->a[i].pExpr;
204       }else{
205         sqlite3ErrorMsg(pParse, "no such column: %s", pChanges->a[i].zName);
206         goto update_cleanup;
207       }
208     }
209 #ifndef SQLITE_OMIT_AUTHORIZATION
210     {
211       int rc;
212       rc = sqlite3AuthCheck(pParse, SQLITE_UPDATE, pTab->zName,
213                            pTab->aCol[j].zName, db->aDb[iDb].zName);
214       if( rc==SQLITE_DENY ){
215         goto update_cleanup;
216       }else if( rc==SQLITE_IGNORE ){
217         aXRef[j] = -1;
218       }
219     }
220 #endif
221   }
222 
223   /* Allocate memory for the array apIdx[] and fill it with pointers to every
224   ** index that needs to be updated.  Indices only need updating if their
225   ** key includes one of the columns named in pChanges or if the record
226   ** number of the original table entry is changing.
227   */
228   for(nIdx=nIdxTotal=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, nIdxTotal++){
229     if( chngRowid ){
230       i = 0;
231     }else {
232       for(i=0; i<pIdx->nColumn; i++){
233         if( aXRef[pIdx->aiColumn[i]]>=0 ) break;
234       }
235     }
236     if( i<pIdx->nColumn ) nIdx++;
237   }
238   if( nIdxTotal>0 ){
239     apIdx = sqlite3DbMallocRaw(db, sizeof(Index*) * nIdx + nIdxTotal );
240     if( apIdx==0 ) goto update_cleanup;
241     aIdxUsed = (char*)&apIdx[nIdx];
242   }
243   for(nIdx=j=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, j++){
244     if( chngRowid ){
245       i = 0;
246     }else{
247       for(i=0; i<pIdx->nColumn; i++){
248         if( aXRef[pIdx->aiColumn[i]]>=0 ) break;
249       }
250     }
251     if( i<pIdx->nColumn ){
252       apIdx[nIdx++] = pIdx;
253       aIdxUsed[j] = 1;
254     }else{
255       aIdxUsed[j] = 0;
256     }
257   }
258 
259   /* Begin generating code.
260   */
261   v = sqlite3GetVdbe(pParse);
262   if( v==0 ) goto update_cleanup;
263   if( pParse->nested==0 ) sqlite3VdbeCountChanges(v);
264   sqlite3BeginWriteOperation(pParse, 1, iDb);
265   mem1 = pParse->nMem++;
266 
267 #ifndef SQLITE_OMIT_VIRTUALTABLE
268   /* Virtual tables must be handled separately */
269   if( IsVirtual(pTab) ){
270     updateVirtualTable(pParse, pTabList, pTab, pChanges, pRowidExpr, aXRef,
271                        pWhere);
272     pWhere = 0;
273     pTabList = 0;
274     goto update_cleanup;
275   }
276 #endif
277 
278   /* Resolve the column names in all the expressions in the
279   ** WHERE clause.
280   */
281   if( sqlite3ExprResolveNames(&sNC, pWhere) ){
282     goto update_cleanup;
283   }
284 
285   /* Start the view context
286   */
287   if( isView ){
288     sqlite3AuthContextPush(pParse, &sContext, pTab->zName);
289   }
290 
291   /* If we are trying to update a view, realize that view into
292   ** a ephemeral table.
293   */
294   if( isView ){
295     Select *pView;
296     pView = sqlite3SelectDup(db, pTab->pSelect);
297     sqlite3Select(pParse, pView, SRT_EphemTab, iCur, 0, 0, 0, 0);
298     sqlite3SelectDelete(pView);
299   }
300 
301   /* Begin the database scan
302   */
303   pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, 0);
304   if( pWInfo==0 ) goto update_cleanup;
305 
306   /* Remember the rowid of every item to be updated.
307   */
308   sqlite3VdbeAddOp(v, IsVirtual(pTab) ? OP_VRowid : OP_Rowid, iCur, 0);
309   sqlite3VdbeAddOp(v, OP_FifoWrite, 0, 0);
310 
311   /* End the database scan loop.
312   */
313   sqlite3WhereEnd(pWInfo);
314 
315   /* Initialize the count of updated rows
316   */
317   if( db->flags & SQLITE_CountRows && !pParse->trigStack ){
318     memCnt = pParse->nMem++;
319     sqlite3VdbeAddOp(v, OP_MemInt, 0, memCnt);
320   }
321 
322   if( triggers_exist ){
323 
324     /* Create pseudo-tables for NEW and OLD
325     */
326     sqlite3VdbeAddOp(v, OP_OpenPseudo, oldIdx, 0);
327     sqlite3VdbeAddOp(v, OP_SetNumColumns, oldIdx, pTab->nCol);
328     sqlite3VdbeAddOp(v, OP_OpenPseudo, newIdx, 0);
329     sqlite3VdbeAddOp(v, OP_SetNumColumns, newIdx, pTab->nCol);
330 
331     /* The top of the update loop for when there are triggers.
332     */
333     addr = sqlite3VdbeAddOp(v, OP_FifoRead, 0, 0);
334     sqlite3VdbeAddOp(v, OP_StackDepth, -1, 0);
335     sqlite3VdbeAddOp(v, OP_MemStore, mem1, 0);
336 
337     if( !isView ){
338       /* Open a cursor and make it point to the record that is
339       ** being updated.
340       */
341       sqlite3OpenTable(pParse, iCur, iDb, pTab, OP_OpenRead);
342     }
343     sqlite3VdbeAddOp(v, OP_NotExists, iCur, addr);
344 
345     /* Generate the OLD table
346     */
347     sqlite3VdbeAddOp(v, OP_Rowid, iCur, 0);
348     sqlite3VdbeAddOp(v, OP_RowData, iCur, 0);
349     sqlite3VdbeAddOp(v, OP_Insert, oldIdx, 0);
350 
351     /* Generate the NEW table
352     */
353     if( chngRowid ){
354       sqlite3ExprCodeAndCache(pParse, pRowidExpr);
355     }else{
356       sqlite3VdbeAddOp(v, OP_Rowid, iCur, 0);
357     }
358     for(i=0; i<pTab->nCol; i++){
359       if( i==pTab->iPKey ){
360         sqlite3VdbeAddOp(v, OP_Null, 0, 0);
361         continue;
362       }
363       j = aXRef[i];
364       if( j<0 ){
365         sqlite3VdbeAddOp(v, OP_Column, iCur, i);
366         sqlite3ColumnDefault(v, pTab, i);
367       }else{
368         sqlite3ExprCodeAndCache(pParse, pChanges->a[j].pExpr);
369       }
370     }
371     sqlite3VdbeAddOp(v, OP_MakeRecord, pTab->nCol, 0);
372     if( !isView ){
373       sqlite3TableAffinityStr(v, pTab);
374     }
375     if( pParse->nErr ) goto update_cleanup;
376     sqlite3VdbeAddOp(v, OP_Insert, newIdx, 0);
377     if( !isView ){
378       sqlite3VdbeAddOp(v, OP_Close, iCur, 0);
379     }
380 
381     /* Fire the BEFORE and INSTEAD OF triggers
382     */
383     if( sqlite3CodeRowTrigger(pParse, TK_UPDATE, pChanges, TRIGGER_BEFORE, pTab,
384           newIdx, oldIdx, onError, addr) ){
385       goto update_cleanup;
386     }
387 
388     if( !isView ){
389       sqlite3VdbeAddOp(v, OP_MemLoad, mem1, 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_StackDepth, -1, 0);
431       sqlite3VdbeAddOp(v, OP_MemStore, mem1, 0);
432     }
433     sqlite3VdbeAddOp(v, OP_NotExists, iCur, addr);
434     sqlite3VdbeAddOp(v, OP_MemLoad, mem1, 0);
435 
436     /* If the record number will change, push the record number as it
437     ** will be after the update. (The old record number is currently
438     ** on top of the stack.)
439     */
440     if( chngRowid ){
441       sqlite3ExprCode(pParse, pRowidExpr);
442       sqlite3VdbeAddOp(v, OP_MustBeInt, 0, 0);
443     }
444 
445     /* Compute new data for this record.
446     */
447     for(i=0; i<pTab->nCol; i++){
448       if( i==pTab->iPKey ){
449         sqlite3VdbeAddOp(v, OP_Null, 0, 0);
450         continue;
451       }
452       j = aXRef[i];
453       if( j<0 ){
454         sqlite3VdbeAddOp(v, OP_Column, iCur, i);
455         sqlite3ColumnDefault(v, pTab, i);
456       }else{
457         sqlite3ExprCode(pParse, pChanges->a[j].pExpr);
458       }
459     }
460 
461     /* Do constraint checks
462     */
463     sqlite3GenerateConstraintChecks(pParse, pTab, iCur, aIdxUsed, chngRowid, 1,
464                                    onError, addr);
465 
466     /* Delete the old indices for the current record.
467     */
468     sqlite3GenerateRowIndexDelete(v, pTab, iCur, aIdxUsed);
469 
470     /* If changing the record number, delete the old record.
471     */
472     if( chngRowid ){
473       sqlite3VdbeAddOp(v, OP_Delete, iCur, 0);
474     }
475 
476     /* Create the new index entries and the new record.
477     */
478     sqlite3CompleteInsertion(pParse, pTab, iCur, aIdxUsed, chngRowid, 1, -1, 0);
479   }
480 
481   /* Increment the row counter
482   */
483   if( db->flags & SQLITE_CountRows && !pParse->trigStack){
484     sqlite3VdbeAddOp(v, OP_MemIncr, 1, memCnt);
485   }
486 
487   /* If there are triggers, close all the cursors after each iteration
488   ** through the loop.  The fire the after triggers.
489   */
490   if( triggers_exist ){
491     if( !isView ){
492       for(i=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, i++){
493         if( openAll || aIdxUsed[i] )
494           sqlite3VdbeAddOp(v, OP_Close, iCur+i+1, 0);
495       }
496       sqlite3VdbeAddOp(v, OP_Close, iCur, 0);
497     }
498     if( sqlite3CodeRowTrigger(pParse, TK_UPDATE, pChanges, TRIGGER_AFTER, pTab,
499           newIdx, oldIdx, onError, addr) ){
500       goto update_cleanup;
501     }
502   }
503 
504   /* Repeat the above with the next record to be updated, until
505   ** all record selected by the WHERE clause have been updated.
506   */
507   sqlite3VdbeAddOp(v, OP_Goto, 0, addr);
508   sqlite3VdbeJumpHere(v, addr);
509 
510   /* Close all tables if there were no FOR EACH ROW triggers */
511   if( !triggers_exist ){
512     for(i=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, i++){
513       if( openAll || aIdxUsed[i] ){
514         sqlite3VdbeAddOp(v, OP_Close, iCur+i+1, 0);
515       }
516     }
517     sqlite3VdbeAddOp(v, OP_Close, iCur, 0);
518   }else{
519     sqlite3VdbeAddOp(v, OP_Close, newIdx, 0);
520     sqlite3VdbeAddOp(v, OP_Close, oldIdx, 0);
521   }
522 
523   /*
524   ** Return the number of rows that were changed. If this routine is
525   ** generating code because of a call to sqlite3NestedParse(), do not
526   ** invoke the callback function.
527   */
528   if( db->flags & SQLITE_CountRows && !pParse->trigStack && pParse->nested==0 ){
529     sqlite3VdbeAddOp(v, OP_MemLoad, memCnt, 0);
530     sqlite3VdbeAddOp(v, OP_Callback, 1, 0);
531     sqlite3VdbeSetNumCols(v, 1);
532     sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "rows updated", P3_STATIC);
533   }
534 
535 update_cleanup:
536   sqlite3AuthContextPop(&sContext);
537   sqlite3_free(apIdx);
538   sqlite3_free(aXRef);
539   sqlite3SrcListDelete(pTabList);
540   sqlite3ExprListDelete(pChanges);
541   sqlite3ExprDelete(pWhere);
542   return;
543 }
544 
545 #ifndef SQLITE_OMIT_VIRTUALTABLE
546 /*
547 ** Generate code for an UPDATE of a virtual table.
548 **
549 ** The strategy is that we create an ephemerial table that contains
550 ** for each row to be changed:
551 **
552 **   (A)  The original rowid of that row.
553 **   (B)  The revised rowid for the row. (note1)
554 **   (C)  The content of every column in the row.
555 **
556 ** Then we loop over this ephemeral table and for each row in
557 ** the ephermeral table call VUpdate.
558 **
559 ** When finished, drop the ephemeral table.
560 **
561 ** (note1) Actually, if we know in advance that (A) is always the same
562 ** as (B) we only store (A), then duplicate (A) when pulling
563 ** it out of the ephemeral table before calling VUpdate.
564 */
565 static void updateVirtualTable(
566   Parse *pParse,       /* The parsing context */
567   SrcList *pSrc,       /* The virtual table to be modified */
568   Table *pTab,         /* The virtual table */
569   ExprList *pChanges,  /* The columns to change in the UPDATE statement */
570   Expr *pRowid,        /* Expression used to recompute the rowid */
571   int *aXRef,          /* Mapping from columns of pTab to entries in pChanges */
572   Expr *pWhere         /* WHERE clause of the UPDATE statement */
573 ){
574   Vdbe *v = pParse->pVdbe;  /* Virtual machine under construction */
575   ExprList *pEList = 0;     /* The result set of the SELECT statement */
576   Select *pSelect = 0;      /* The SELECT statement */
577   Expr *pExpr;              /* Temporary expression */
578   int ephemTab;             /* Table holding the result of the SELECT */
579   int i;                    /* Loop counter */
580   int addr;                 /* Address of top of loop */
581   sqlite3 *db = pParse->db; /* Database connection */
582 
583   /* Construct the SELECT statement that will find the new values for
584   ** all updated rows.
585   */
586   pEList = sqlite3ExprListAppend(pParse, 0,
587                                  sqlite3CreateIdExpr(pParse, "_rowid_"), 0);
588   if( pRowid ){
589     pEList = sqlite3ExprListAppend(pParse, pEList,
590                                    sqlite3ExprDup(db, pRowid), 0);
591   }
592   assert( pTab->iPKey<0 );
593   for(i=0; i<pTab->nCol; i++){
594     if( aXRef[i]>=0 ){
595       pExpr = sqlite3ExprDup(db, pChanges->a[aXRef[i]].pExpr);
596     }else{
597       pExpr = sqlite3CreateIdExpr(pParse, pTab->aCol[i].zName);
598     }
599     pEList = sqlite3ExprListAppend(pParse, pEList, pExpr, 0);
600   }
601   pSelect = sqlite3SelectNew(pParse, pEList, pSrc, pWhere, 0, 0, 0, 0, 0, 0);
602 
603   /* Create the ephemeral table into which the update results will
604   ** be stored.
605   */
606   assert( v );
607   ephemTab = pParse->nTab++;
608   sqlite3VdbeAddOp(v, OP_OpenEphemeral, ephemTab, pTab->nCol+1+(pRowid!=0));
609 
610   /* fill the ephemeral table
611   */
612   sqlite3Select(pParse, pSelect, SRT_Table, ephemTab, 0, 0, 0, 0);
613 
614   /*
615   ** Generate code to scan the ephemeral table and call VDelete and
616   ** VInsert
617   */
618   sqlite3VdbeAddOp(v, OP_Rewind, ephemTab, 0);
619   addr = sqlite3VdbeCurrentAddr(v);
620   sqlite3VdbeAddOp(v, OP_Column,  ephemTab, 0);
621   if( pRowid ){
622     sqlite3VdbeAddOp(v, OP_Column, ephemTab, 1);
623   }else{
624     sqlite3VdbeAddOp(v, OP_Dup, 0, 0);
625   }
626   for(i=0; i<pTab->nCol; i++){
627     sqlite3VdbeAddOp(v, OP_Column, ephemTab, i+1+(pRowid!=0));
628   }
629   pParse->pVirtualLock = pTab;
630   sqlite3VdbeOp3(v, OP_VUpdate, 0, pTab->nCol+2,
631                      (const char*)pTab->pVtab, P3_VTAB);
632   sqlite3VdbeAddOp(v, OP_Next, ephemTab, addr);
633   sqlite3VdbeJumpHere(v, addr-1);
634   sqlite3VdbeAddOp(v, OP_Close, ephemTab, 0);
635 
636   /* Cleanup */
637   sqlite3SelectDelete(pSelect);
638 }
639 #endif /* SQLITE_OMIT_VIRTUALTABLE */
640