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 : ** $Id$
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 : */
57 428 : void sqlite3ColumnDefault(Vdbe *v, Table *pTab, int i){
58 428 : if( pTab && !pTab->pSelect ){
59 : sqlite3_value *pValue;
60 428 : u8 enc = ENC(sqlite3VdbeDb(v));
61 428 : Column *pCol = &pTab->aCol[i];
62 428 : sqlite3ValueFromExpr(pCol->pDflt, enc, pCol->affinity, &pValue);
63 428 : if( pValue ){
64 0 : sqlite3VdbeChangeP3(v, -1, (const char *)pValue, P3_MEM);
65 : }else{
66 : VdbeComment((v, "# %s.%s", pTab->zName, pCol->zName));
67 : }
68 : }
69 428 : }
70 :
71 : /*
72 : ** Process an UPDATE statement.
73 : **
74 : ** UPDATE OR IGNORE table_wxyz SET a=b, c=d WHERE e<5 AND f NOT NULL;
75 : ** \_______/ \________/ \______/ \________________/
76 : * onError pTabList pChanges pWhere
77 : */
78 : void sqlite3Update(
79 : Parse *pParse, /* The parser context */
80 : SrcList *pTabList, /* The table in which we should change things */
81 : ExprList *pChanges, /* Things to be changed */
82 : Expr *pWhere, /* The WHERE clause. May be null */
83 : int onError /* How to handle constraint errors */
84 64 : ){
85 : int i, j; /* Loop counters */
86 : Table *pTab; /* The table to be updated */
87 64 : int addr = 0; /* VDBE instruction address of the start of the loop */
88 : WhereInfo *pWInfo; /* Information about the WHERE clause */
89 : Vdbe *v; /* The virtual database engine */
90 : Index *pIdx; /* For looping over indices */
91 : int nIdx; /* Number of indices that need updating */
92 : int nIdxTotal; /* Total number of indices */
93 : int iCur; /* VDBE Cursor number of pTab */
94 : sqlite3 *db; /* The database structure */
95 64 : Index **apIdx = 0; /* An array of indices that need updating too */
96 64 : char *aIdxUsed = 0; /* aIdxUsed[i]==1 if the i-th index is used */
97 64 : int *aXRef = 0; /* aXRef[i] is the index in pChanges->a[] of the
98 : ** an expression for the i-th column of the table.
99 : ** aXRef[i]==-1 if the i-th column is not changed. */
100 : int chngRowid; /* True if the record number is being changed */
101 64 : Expr *pRowidExpr = 0; /* Expression defining the new record number */
102 64 : int openAll = 0; /* True if all indices need to be opened */
103 : AuthContext sContext; /* The authorization context */
104 : NameContext sNC; /* The name-context to resolve expressions in */
105 : int iDb; /* Database containing the table being updated */
106 64 : int memCnt = 0; /* Memory cell used for counting rows changed */
107 :
108 : #ifndef SQLITE_OMIT_TRIGGER
109 : int isView; /* Trying to update a view */
110 64 : int triggers_exist = 0; /* True if any row triggers exist */
111 : #endif
112 :
113 64 : int newIdx = -1; /* index of trigger "new" temp table */
114 64 : int oldIdx = -1; /* index of trigger "old" temp table */
115 :
116 64 : sContext.pParse = 0;
117 64 : if( pParse->nErr || sqlite3MallocFailed() ){
118 : goto update_cleanup;
119 : }
120 64 : db = pParse->db;
121 : assert( pTabList->nSrc==1 );
122 :
123 : /* Locate the table which we want to update.
124 : */
125 64 : pTab = sqlite3SrcListLookup(pParse, pTabList);
126 64 : if( pTab==0 ) goto update_cleanup;
127 63 : iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
128 :
129 : /* Figure out if we have any triggers and if the table being
130 : ** updated is a view
131 : */
132 : #ifndef SQLITE_OMIT_TRIGGER
133 63 : triggers_exist = sqlite3TriggersExist(pParse, pTab, TK_UPDATE, pChanges);
134 63 : isView = pTab->pSelect!=0;
135 : #else
136 : # define triggers_exist 0
137 : # define isView 0
138 : #endif
139 : #ifdef SQLITE_OMIT_VIEW
140 : # undef isView
141 : # define isView 0
142 : #endif
143 :
144 63 : if( sqlite3IsReadOnly(pParse, pTab, triggers_exist) ){
145 0 : goto update_cleanup;
146 : }
147 63 : if( sqlite3ViewGetColumnNames(pParse, pTab) ){
148 0 : goto update_cleanup;
149 : }
150 63 : aXRef = sqliteMallocRaw( sizeof(int) * pTab->nCol );
151 63 : if( aXRef==0 ) goto update_cleanup;
152 63 : for(i=0; i<pTab->nCol; i++) aXRef[i] = -1;
153 :
154 : /* If there are FOR EACH ROW triggers, allocate cursors for the
155 : ** special OLD and NEW tables
156 : */
157 63 : if( triggers_exist ){
158 0 : newIdx = pParse->nTab++;
159 0 : oldIdx = pParse->nTab++;
160 : }
161 :
162 : /* Allocate a cursors for the main database table and for all indices.
163 : ** The index cursors might not be used, but if they are used they
164 : ** need to occur right after the database cursor. So go ahead and
165 : ** allocate enough space, just in case.
166 : */
167 63 : pTabList->a[0].iCursor = iCur = pParse->nTab++;
168 63 : for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
169 0 : pParse->nTab++;
170 : }
171 :
172 : /* Initialize the name-context */
173 63 : memset(&sNC, 0, sizeof(sNC));
174 63 : sNC.pParse = pParse;
175 63 : sNC.pSrcList = pTabList;
176 :
177 : /* Resolve the column names in all the expressions of the
178 : ** of the UPDATE statement. Also find the column index
179 : ** for each column to be updated in the pChanges array. For each
180 : ** column to be updated, make sure we have authorization to change
181 : ** that column.
182 : */
183 63 : chngRowid = 0;
184 354 : for(i=0; i<pChanges->nExpr; i++){
185 291 : if( sqlite3ExprResolveNames(&sNC, pChanges->a[i].pExpr) ){
186 0 : goto update_cleanup;
187 : }
188 876 : for(j=0; j<pTab->nCol; j++){
189 876 : if( sqlite3StrICmp(pTab->aCol[j].zName, pChanges->a[i].zName)==0 ){
190 291 : if( j==pTab->iPKey ){
191 0 : chngRowid = 1;
192 0 : pRowidExpr = pChanges->a[i].pExpr;
193 : }
194 291 : aXRef[j] = i;
195 291 : break;
196 : }
197 : }
198 291 : if( j>=pTab->nCol ){
199 0 : if( sqlite3IsRowid(pChanges->a[i].zName) ){
200 0 : chngRowid = 1;
201 0 : pRowidExpr = pChanges->a[i].pExpr;
202 : }else{
203 0 : sqlite3ErrorMsg(pParse, "no such column: %s", pChanges->a[i].zName);
204 0 : goto update_cleanup;
205 : }
206 : }
207 : #ifndef SQLITE_OMIT_AUTHORIZATION
208 : {
209 : int rc;
210 291 : rc = sqlite3AuthCheck(pParse, SQLITE_UPDATE, pTab->zName,
211 : pTab->aCol[j].zName, db->aDb[iDb].zName);
212 291 : if( rc==SQLITE_DENY ){
213 0 : goto update_cleanup;
214 291 : }else if( rc==SQLITE_IGNORE ){
215 0 : aXRef[j] = -1;
216 : }
217 : }
218 : #endif
219 : }
220 :
221 : /* Allocate memory for the array apIdx[] and fill it with pointers to every
222 : ** index that needs to be updated. Indices only need updating if their
223 : ** key includes one of the columns named in pChanges or if the record
224 : ** number of the original table entry is changing.
225 : */
226 63 : for(nIdx=nIdxTotal=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, nIdxTotal++){
227 0 : if( chngRowid ){
228 0 : i = 0;
229 : }else {
230 0 : for(i=0; i<pIdx->nColumn; i++){
231 0 : if( aXRef[pIdx->aiColumn[i]]>=0 ) break;
232 : }
233 : }
234 0 : if( i<pIdx->nColumn ) nIdx++;
235 : }
236 63 : if( nIdxTotal>0 ){
237 0 : apIdx = sqliteMallocRaw( sizeof(Index*) * nIdx + nIdxTotal );
238 0 : if( apIdx==0 ) goto update_cleanup;
239 0 : aIdxUsed = (char*)&apIdx[nIdx];
240 : }
241 63 : for(nIdx=j=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, j++){
242 0 : if( chngRowid ){
243 0 : i = 0;
244 : }else{
245 0 : for(i=0; i<pIdx->nColumn; i++){
246 0 : if( aXRef[pIdx->aiColumn[i]]>=0 ) break;
247 : }
248 : }
249 0 : if( i<pIdx->nColumn ){
250 0 : apIdx[nIdx++] = pIdx;
251 0 : aIdxUsed[j] = 1;
252 : }else{
253 0 : aIdxUsed[j] = 0;
254 : }
255 : }
256 :
257 : /* Begin generating code.
258 : */
259 63 : v = sqlite3GetVdbe(pParse);
260 63 : if( v==0 ) goto update_cleanup;
261 63 : if( pParse->nested==0 ) sqlite3VdbeCountChanges(v);
262 63 : sqlite3BeginWriteOperation(pParse, 1, iDb);
263 :
264 : #ifndef SQLITE_OMIT_VIRTUALTABLE
265 : /* Virtual tables must be handled separately */
266 63 : if( IsVirtual(pTab) ){
267 0 : updateVirtualTable(pParse, pTabList, pTab, pChanges, pRowidExpr, aXRef,
268 : pWhere);
269 0 : pWhere = 0;
270 0 : pTabList = 0;
271 0 : goto update_cleanup;
272 : }
273 : #endif
274 :
275 : /* Resolve the column names in all the expressions in the
276 : ** WHERE clause.
277 : */
278 63 : if( sqlite3ExprResolveNames(&sNC, pWhere) ){
279 0 : goto update_cleanup;
280 : }
281 :
282 : /* Start the view context
283 : */
284 63 : if( isView ){
285 0 : sqlite3AuthContextPush(pParse, &sContext, pTab->zName);
286 : }
287 :
288 : /* If we are trying to update a view, realize that view into
289 : ** a ephemeral table.
290 : */
291 63 : if( isView ){
292 : Select *pView;
293 0 : pView = sqlite3SelectDup(pTab->pSelect);
294 0 : sqlite3Select(pParse, pView, SRT_EphemTab, iCur, 0, 0, 0, 0);
295 0 : sqlite3SelectDelete(pView);
296 : }
297 :
298 : /* Begin the database scan
299 : */
300 63 : pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, 0);
301 63 : if( pWInfo==0 ) goto update_cleanup;
302 :
303 : /* Remember the rowid of every item to be updated.
304 : */
305 63 : sqlite3VdbeAddOp(v, IsVirtual(pTab) ? OP_VRowid : OP_Rowid, iCur, 0);
306 63 : sqlite3VdbeAddOp(v, OP_FifoWrite, 0, 0);
307 :
308 : /* End the database scan loop.
309 : */
310 63 : sqlite3WhereEnd(pWInfo);
311 :
312 : /* Initialize the count of updated rows
313 : */
314 63 : if( db->flags & SQLITE_CountRows && !pParse->trigStack ){
315 0 : memCnt = pParse->nMem++;
316 0 : sqlite3VdbeAddOp(v, OP_MemInt, 0, memCnt);
317 : }
318 :
319 63 : if( triggers_exist ){
320 : /* Create pseudo-tables for NEW and OLD
321 : */
322 0 : sqlite3VdbeAddOp(v, OP_OpenPseudo, oldIdx, 0);
323 0 : sqlite3VdbeAddOp(v, OP_SetNumColumns, oldIdx, pTab->nCol);
324 0 : sqlite3VdbeAddOp(v, OP_OpenPseudo, newIdx, 0);
325 0 : sqlite3VdbeAddOp(v, OP_SetNumColumns, newIdx, pTab->nCol);
326 :
327 : /* The top of the update loop for when there are triggers.
328 : */
329 0 : addr = sqlite3VdbeAddOp(v, OP_FifoRead, 0, 0);
330 :
331 0 : if( !isView ){
332 0 : sqlite3VdbeAddOp(v, OP_Dup, 0, 0);
333 0 : sqlite3VdbeAddOp(v, OP_Dup, 0, 0);
334 : /* Open a cursor and make it point to the record that is
335 : ** being updated.
336 : */
337 0 : sqlite3OpenTable(pParse, iCur, iDb, pTab, OP_OpenRead);
338 : }
339 0 : sqlite3VdbeAddOp(v, OP_MoveGe, iCur, 0);
340 :
341 : /* Generate the OLD table
342 : */
343 0 : sqlite3VdbeAddOp(v, OP_Rowid, iCur, 0);
344 0 : sqlite3VdbeAddOp(v, OP_RowData, iCur, 0);
345 0 : sqlite3VdbeAddOp(v, OP_Insert, oldIdx, 0);
346 :
347 : /* Generate the NEW table
348 : */
349 0 : if( chngRowid ){
350 0 : sqlite3ExprCodeAndCache(pParse, pRowidExpr);
351 : }else{
352 0 : sqlite3VdbeAddOp(v, OP_Rowid, iCur, 0);
353 : }
354 0 : for(i=0; i<pTab->nCol; i++){
355 0 : if( i==pTab->iPKey ){
356 0 : sqlite3VdbeAddOp(v, OP_Null, 0, 0);
357 0 : continue;
358 : }
359 0 : j = aXRef[i];
360 0 : if( j<0 ){
361 0 : sqlite3VdbeAddOp(v, OP_Column, iCur, i);
362 0 : sqlite3ColumnDefault(v, pTab, i);
363 : }else{
364 0 : sqlite3ExprCodeAndCache(pParse, pChanges->a[j].pExpr);
365 : }
366 : }
367 0 : sqlite3VdbeAddOp(v, OP_MakeRecord, pTab->nCol, 0);
368 0 : if( !isView ){
369 0 : sqlite3TableAffinityStr(v, pTab);
370 : }
371 0 : if( pParse->nErr ) goto update_cleanup;
372 0 : sqlite3VdbeAddOp(v, OP_Insert, newIdx, 0);
373 0 : if( !isView ){
374 0 : sqlite3VdbeAddOp(v, OP_Close, iCur, 0);
375 : }
376 :
377 : /* Fire the BEFORE and INSTEAD OF triggers
378 : */
379 0 : if( sqlite3CodeRowTrigger(pParse, TK_UPDATE, pChanges, TRIGGER_BEFORE, pTab,
380 : newIdx, oldIdx, onError, addr) ){
381 0 : goto update_cleanup;
382 : }
383 : }
384 :
385 63 : if( !isView && !IsVirtual(pTab) ){
386 : /*
387 : ** Open every index that needs updating. Note that if any
388 : ** index could potentially invoke a REPLACE conflict resolution
389 : ** action, then we need to open all indices because we might need
390 : ** to be deleting some records.
391 : */
392 63 : sqlite3OpenTable(pParse, iCur, iDb, pTab, OP_OpenWrite);
393 63 : if( onError==OE_Replace ){
394 0 : openAll = 1;
395 : }else{
396 63 : openAll = 0;
397 63 : for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
398 0 : if( pIdx->onError==OE_Replace ){
399 0 : openAll = 1;
400 0 : break;
401 : }
402 : }
403 : }
404 63 : for(i=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, i++){
405 0 : if( openAll || aIdxUsed[i] ){
406 0 : KeyInfo *pKey = sqlite3IndexKeyinfo(pParse, pIdx);
407 0 : sqlite3VdbeAddOp(v, OP_Integer, iDb, 0);
408 0 : sqlite3VdbeOp3(v, OP_OpenWrite, iCur+i+1, pIdx->tnum,
409 : (char*)pKey, P3_KEYINFO_HANDOFF);
410 : assert( pParse->nTab>iCur+i+1 );
411 : }
412 : }
413 :
414 : /* Loop over every record that needs updating. We have to load
415 : ** the old data for each record to be updated because some columns
416 : ** might not change and we will need to copy the old value.
417 : ** Also, the old data is needed to delete the old index entries.
418 : ** So make the cursor point at the old record.
419 : */
420 63 : if( !triggers_exist ){
421 63 : addr = sqlite3VdbeAddOp(v, OP_FifoRead, 0, 0);
422 63 : sqlite3VdbeAddOp(v, OP_Dup, 0, 0);
423 : }
424 63 : sqlite3VdbeAddOp(v, OP_NotExists, iCur, addr);
425 :
426 : /* If the record number will change, push the record number as it
427 : ** will be after the update. (The old record number is currently
428 : ** on top of the stack.)
429 : */
430 63 : if( chngRowid ){
431 0 : sqlite3ExprCode(pParse, pRowidExpr);
432 0 : sqlite3VdbeAddOp(v, OP_MustBeInt, 0, 0);
433 : }
434 :
435 : /* Compute new data for this record.
436 : */
437 374 : for(i=0; i<pTab->nCol; i++){
438 311 : if( i==pTab->iPKey ){
439 0 : sqlite3VdbeAddOp(v, OP_Null, 0, 0);
440 0 : continue;
441 : }
442 311 : j = aXRef[i];
443 311 : if( j<0 ){
444 20 : sqlite3VdbeAddOp(v, OP_Column, iCur, i);
445 20 : sqlite3ColumnDefault(v, pTab, i);
446 : }else{
447 291 : sqlite3ExprCode(pParse, pChanges->a[j].pExpr);
448 : }
449 : }
450 :
451 : /* Do constraint checks
452 : */
453 63 : sqlite3GenerateConstraintChecks(pParse, pTab, iCur, aIdxUsed, chngRowid, 1,
454 : onError, addr);
455 :
456 : /* Delete the old indices for the current record.
457 : */
458 63 : sqlite3GenerateRowIndexDelete(v, pTab, iCur, aIdxUsed);
459 :
460 : /* If changing the record number, delete the old record.
461 : */
462 63 : if( chngRowid ){
463 0 : sqlite3VdbeAddOp(v, OP_Delete, iCur, 0);
464 : }
465 :
466 : /* Create the new index entries and the new record.
467 : */
468 63 : sqlite3CompleteInsertion(pParse, pTab, iCur, aIdxUsed, chngRowid, 1, -1, 0);
469 : }
470 :
471 : /* Increment the row counter
472 : */
473 63 : if( db->flags & SQLITE_CountRows && !pParse->trigStack){
474 0 : sqlite3VdbeAddOp(v, OP_MemIncr, 1, memCnt);
475 : }
476 :
477 : /* If there are triggers, close all the cursors after each iteration
478 : ** through the loop. The fire the after triggers.
479 : */
480 63 : if( triggers_exist ){
481 0 : if( !isView ){
482 0 : for(i=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, i++){
483 0 : if( openAll || aIdxUsed[i] )
484 0 : sqlite3VdbeAddOp(v, OP_Close, iCur+i+1, 0);
485 : }
486 0 : sqlite3VdbeAddOp(v, OP_Close, iCur, 0);
487 : }
488 0 : if( sqlite3CodeRowTrigger(pParse, TK_UPDATE, pChanges, TRIGGER_AFTER, pTab,
489 : newIdx, oldIdx, onError, addr) ){
490 0 : goto update_cleanup;
491 : }
492 : }
493 :
494 : /* Repeat the above with the next record to be updated, until
495 : ** all record selected by the WHERE clause have been updated.
496 : */
497 63 : sqlite3VdbeAddOp(v, OP_Goto, 0, addr);
498 63 : sqlite3VdbeJumpHere(v, addr);
499 :
500 : /* Close all tables if there were no FOR EACH ROW triggers */
501 63 : if( !triggers_exist ){
502 63 : for(i=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, i++){
503 0 : if( openAll || aIdxUsed[i] ){
504 0 : sqlite3VdbeAddOp(v, OP_Close, iCur+i+1, 0);
505 : }
506 : }
507 63 : sqlite3VdbeAddOp(v, OP_Close, iCur, 0);
508 : }else{
509 0 : sqlite3VdbeAddOp(v, OP_Close, newIdx, 0);
510 0 : sqlite3VdbeAddOp(v, OP_Close, oldIdx, 0);
511 : }
512 :
513 : /*
514 : ** Return the number of rows that were changed. If this routine is
515 : ** generating code because of a call to sqlite3NestedParse(), do not
516 : ** invoke the callback function.
517 : */
518 63 : if( db->flags & SQLITE_CountRows && !pParse->trigStack && pParse->nested==0 ){
519 0 : sqlite3VdbeAddOp(v, OP_MemLoad, memCnt, 0);
520 0 : sqlite3VdbeAddOp(v, OP_Callback, 1, 0);
521 0 : sqlite3VdbeSetNumCols(v, 1);
522 0 : sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "rows updated", P3_STATIC);
523 : }
524 :
525 64 : update_cleanup:
526 64 : sqlite3AuthContextPop(&sContext);
527 64 : sqliteFree(apIdx);
528 64 : sqliteFree(aXRef);
529 64 : sqlite3SrcListDelete(pTabList);
530 64 : sqlite3ExprListDelete(pChanges);
531 64 : sqlite3ExprDelete(pWhere);
532 : return;
533 : }
534 :
535 : #ifndef SQLITE_OMIT_VIRTUALTABLE
536 : /*
537 : ** Generate code for an UPDATE of a virtual table.
538 : **
539 : ** The strategy is that we create an ephemerial table that contains
540 : ** for each row to be changed:
541 : **
542 : ** (A) The original rowid of that row.
543 : ** (B) The revised rowid for the row. (note1)
544 : ** (C) The content of every column in the row.
545 : **
546 : ** Then we loop over this ephemeral table and for each row in
547 : ** the ephermeral table call VUpdate.
548 : **
549 : ** When finished, drop the ephemeral table.
550 : **
551 : ** (note1) Actually, if we know in advance that (A) is always the same
552 : ** as (B) we only store (A), then duplicate (A) when pulling
553 : ** it out of the ephemeral table before calling VUpdate.
554 : */
555 : static void updateVirtualTable(
556 : Parse *pParse, /* The parsing context */
557 : SrcList *pSrc, /* The virtual table to be modified */
558 : Table *pTab, /* The virtual table */
559 : ExprList *pChanges, /* The columns to change in the UPDATE statement */
560 : Expr *pRowid, /* Expression used to recompute the rowid */
561 : int *aXRef, /* Mapping from columns of pTab to entries in pChanges */
562 : Expr *pWhere /* WHERE clause of the UPDATE statement */
563 0 : ){
564 0 : Vdbe *v = pParse->pVdbe; /* Virtual machine under construction */
565 0 : ExprList *pEList = 0; /* The result set of the SELECT statement */
566 0 : Select *pSelect = 0; /* The SELECT statement */
567 : Expr *pExpr; /* Temporary expression */
568 : int ephemTab; /* Table holding the result of the SELECT */
569 : int i; /* Loop counter */
570 : int addr; /* Address of top of loop */
571 :
572 : /* Construct the SELECT statement that will find the new values for
573 : ** all updated rows.
574 : */
575 0 : pEList = sqlite3ExprListAppend(0, sqlite3CreateIdExpr("_rowid_"), 0);
576 0 : if( pRowid ){
577 0 : pEList = sqlite3ExprListAppend(pEList, sqlite3ExprDup(pRowid), 0);
578 : }
579 : assert( pTab->iPKey<0 );
580 0 : for(i=0; i<pTab->nCol; i++){
581 0 : if( aXRef[i]>=0 ){
582 0 : pExpr = sqlite3ExprDup(pChanges->a[aXRef[i]].pExpr);
583 : }else{
584 0 : pExpr = sqlite3CreateIdExpr(pTab->aCol[i].zName);
585 : }
586 0 : pEList = sqlite3ExprListAppend(pEList, pExpr, 0);
587 : }
588 0 : pSelect = sqlite3SelectNew(pEList, pSrc, pWhere, 0, 0, 0, 0, 0, 0);
589 :
590 : /* Create the ephemeral table into which the update results will
591 : ** be stored.
592 : */
593 : assert( v );
594 0 : ephemTab = pParse->nTab++;
595 0 : sqlite3VdbeAddOp(v, OP_OpenEphemeral, ephemTab, pTab->nCol+1+(pRowid!=0));
596 :
597 : /* fill the ephemeral table
598 : */
599 0 : sqlite3Select(pParse, pSelect, SRT_Table, ephemTab, 0, 0, 0, 0);
600 :
601 : /*
602 : ** Generate code to scan the ephemeral table and call VDelete and
603 : ** VInsert
604 : */
605 0 : sqlite3VdbeAddOp(v, OP_Rewind, ephemTab, 0);
606 0 : addr = sqlite3VdbeCurrentAddr(v);
607 0 : sqlite3VdbeAddOp(v, OP_Column, ephemTab, 0);
608 0 : if( pRowid ){
609 0 : sqlite3VdbeAddOp(v, OP_Column, ephemTab, 1);
610 : }else{
611 0 : sqlite3VdbeAddOp(v, OP_Dup, 0, 0);
612 : }
613 0 : for(i=0; i<pTab->nCol; i++){
614 0 : sqlite3VdbeAddOp(v, OP_Column, ephemTab, i+1+(pRowid!=0));
615 : }
616 0 : pParse->pVirtualLock = pTab;
617 0 : sqlite3VdbeOp3(v, OP_VUpdate, 0, pTab->nCol+2,
618 : (const char*)pTab->pVtab, P3_VTAB);
619 0 : sqlite3VdbeAddOp(v, OP_Next, ephemTab, addr);
620 0 : sqlite3VdbeJumpHere(v, addr-1);
621 0 : sqlite3VdbeAddOp(v, OP_Close, ephemTab, 0);
622 :
623 : /* Cleanup */
624 0 : sqlite3SelectDelete(pSelect);
625 0 : }
626 : #endif /* SQLITE_OMIT_VIRTUALTABLE */
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