1 : /*
2 : ** 2001 September 15
3 : **
4 : ** The author disclaims copyright to this source code. In place of
5 : ** a legal notice, here is a blessing:
6 : **
7 : ** May you do good and not evil.
8 : ** May you find forgiveness for yourself and forgive others.
9 : ** May you share freely, never taking more than you give.
10 : **
11 : *************************************************************************
12 : ** This file contains C code routines that are called by the parser
13 : ** in order to generate code for DELETE FROM statements.
14 : **
15 : ** $Id$
16 : */
17 : #include "sqliteInt.h"
18 :
19 : /*
20 : ** Look up every table that is named in pSrc. If any table is not found,
21 : ** add an error message to pParse->zErrMsg and return NULL. If all tables
22 : ** are found, return a pointer to the last table.
23 : */
24 229 : Table *sqlite3SrcListLookup(Parse *pParse, SrcList *pSrc){
25 229 : Table *pTab = 0;
26 : int i;
27 : struct SrcList_item *pItem;
28 458 : for(i=0, pItem=pSrc->a; i<pSrc->nSrc; i++, pItem++){
29 229 : pTab = sqlite3LocateTable(pParse, pItem->zName, pItem->zDatabase);
30 229 : sqlite3DeleteTable(pItem->pTab);
31 229 : pItem->pTab = pTab;
32 229 : if( pTab ){
33 228 : pTab->nRef++;
34 : }
35 : }
36 229 : return pTab;
37 : }
38 :
39 : /*
40 : ** Check to make sure the given table is writable. If it is not
41 : ** writable, generate an error message and return 1. If it is
42 : ** writable return 0;
43 : */
44 228 : int sqlite3IsReadOnly(Parse *pParse, Table *pTab, int viewOk){
45 228 : if( (pTab->readOnly && (pParse->db->flags & SQLITE_WriteSchema)==0
46 : && pParse->nested==0)
47 : #ifndef SQLITE_OMIT_VIRTUALTABLE
48 : || (pTab->pMod && pTab->pMod->pModule->xUpdate==0)
49 : #endif
50 : ){
51 0 : sqlite3ErrorMsg(pParse, "table %s may not be modified", pTab->zName);
52 0 : return 1;
53 : }
54 : #ifndef SQLITE_OMIT_VIEW
55 228 : if( !viewOk && pTab->pSelect ){
56 0 : sqlite3ErrorMsg(pParse,"cannot modify %s because it is a view",pTab->zName);
57 0 : return 1;
58 : }
59 : #endif
60 228 : return 0;
61 : }
62 :
63 : /*
64 : ** Generate code that will open a table for reading.
65 : */
66 : void sqlite3OpenTable(
67 : Parse *p, /* Generate code into this VDBE */
68 : int iCur, /* The cursor number of the table */
69 : int iDb, /* The database index in sqlite3.aDb[] */
70 : Table *pTab, /* The table to be opened */
71 : int opcode /* OP_OpenRead or OP_OpenWrite */
72 442 : ){
73 : Vdbe *v;
74 442 : if( IsVirtual(pTab) ) return;
75 442 : v = sqlite3GetVdbe(p);
76 : assert( opcode==OP_OpenWrite || opcode==OP_OpenRead );
77 442 : sqlite3TableLock(p, iDb, pTab->tnum, (opcode==OP_OpenWrite), pTab->zName);
78 442 : sqlite3VdbeAddOp(v, OP_Integer, iDb, 0);
79 : VdbeComment((v, "# %s", pTab->zName));
80 442 : sqlite3VdbeAddOp(v, opcode, iCur, pTab->tnum);
81 442 : sqlite3VdbeAddOp(v, OP_SetNumColumns, iCur, pTab->nCol);
82 : }
83 :
84 :
85 : /*
86 : ** Generate code for a DELETE FROM statement.
87 : **
88 : ** DELETE FROM table_wxyz WHERE a<5 AND b NOT NULL;
89 : ** \________/ \________________/
90 : ** pTabList pWhere
91 : */
92 : void sqlite3DeleteFrom(
93 : Parse *pParse, /* The parser context */
94 : SrcList *pTabList, /* The table from which we should delete things */
95 : Expr *pWhere /* The WHERE clause. May be null */
96 6 : ){
97 : Vdbe *v; /* The virtual database engine */
98 : Table *pTab; /* The table from which records will be deleted */
99 : const char *zDb; /* Name of database holding pTab */
100 6 : int end, addr = 0; /* A couple addresses of generated code */
101 : int i; /* Loop counter */
102 : WhereInfo *pWInfo; /* Information about the WHERE clause */
103 : Index *pIdx; /* For looping over indices of the table */
104 : int iCur; /* VDBE Cursor number for pTab */
105 : sqlite3 *db; /* Main database structure */
106 : AuthContext sContext; /* Authorization context */
107 6 : int oldIdx = -1; /* Cursor for the OLD table of AFTER triggers */
108 : NameContext sNC; /* Name context to resolve expressions in */
109 : int iDb; /* Database number */
110 6 : int memCnt = 0; /* Memory cell used for change counting */
111 :
112 : #ifndef SQLITE_OMIT_TRIGGER
113 : int isView; /* True if attempting to delete from a view */
114 6 : int triggers_exist = 0; /* True if any triggers exist */
115 : #endif
116 :
117 6 : sContext.pParse = 0;
118 6 : if( pParse->nErr || sqlite3MallocFailed() ){
119 : goto delete_from_cleanup;
120 : }
121 6 : db = pParse->db;
122 : assert( pTabList->nSrc==1 );
123 :
124 : /* Locate the table which we want to delete. This table has to be
125 : ** put in an SrcList structure because some of the subroutines we
126 : ** will be calling are designed to work with multiple tables and expect
127 : ** an SrcList* parameter instead of just a Table* parameter.
128 : */
129 6 : pTab = sqlite3SrcListLookup(pParse, pTabList);
130 6 : if( pTab==0 ) goto delete_from_cleanup;
131 :
132 : /* Figure out if we have any triggers and if the table being
133 : ** deleted from is a view
134 : */
135 : #ifndef SQLITE_OMIT_TRIGGER
136 6 : triggers_exist = sqlite3TriggersExist(pParse, pTab, TK_DELETE, 0);
137 6 : isView = pTab->pSelect!=0;
138 : #else
139 : # define triggers_exist 0
140 : # define isView 0
141 : #endif
142 : #ifdef SQLITE_OMIT_VIEW
143 : # undef isView
144 : # define isView 0
145 : #endif
146 :
147 6 : if( sqlite3IsReadOnly(pParse, pTab, triggers_exist) ){
148 0 : goto delete_from_cleanup;
149 : }
150 6 : iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
151 : assert( iDb<db->nDb );
152 6 : zDb = db->aDb[iDb].zName;
153 6 : if( sqlite3AuthCheck(pParse, SQLITE_DELETE, pTab->zName, 0, zDb) ){
154 0 : goto delete_from_cleanup;
155 : }
156 :
157 : /* If pTab is really a view, make sure it has been initialized.
158 : */
159 6 : if( sqlite3ViewGetColumnNames(pParse, pTab) ){
160 0 : goto delete_from_cleanup;
161 : }
162 :
163 : /* Allocate a cursor used to store the old.* data for a trigger.
164 : */
165 6 : if( triggers_exist ){
166 0 : oldIdx = pParse->nTab++;
167 : }
168 :
169 : /* Resolve the column names in the WHERE clause.
170 : */
171 : assert( pTabList->nSrc==1 );
172 6 : iCur = pTabList->a[0].iCursor = pParse->nTab++;
173 6 : memset(&sNC, 0, sizeof(sNC));
174 6 : sNC.pParse = pParse;
175 6 : sNC.pSrcList = pTabList;
176 6 : if( sqlite3ExprResolveNames(&sNC, pWhere) ){
177 0 : goto delete_from_cleanup;
178 : }
179 :
180 : /* Start the view context
181 : */
182 6 : if( isView ){
183 0 : sqlite3AuthContextPush(pParse, &sContext, pTab->zName);
184 : }
185 :
186 : /* Begin generating code.
187 : */
188 6 : v = sqlite3GetVdbe(pParse);
189 6 : if( v==0 ){
190 0 : goto delete_from_cleanup;
191 : }
192 6 : if( pParse->nested==0 ) sqlite3VdbeCountChanges(v);
193 6 : sqlite3BeginWriteOperation(pParse, triggers_exist, iDb);
194 :
195 : /* If we are trying to delete from a view, realize that view into
196 : ** a ephemeral table.
197 : */
198 6 : if( isView ){
199 0 : Select *pView = sqlite3SelectDup(pTab->pSelect);
200 0 : sqlite3Select(pParse, pView, SRT_EphemTab, iCur, 0, 0, 0, 0);
201 0 : sqlite3SelectDelete(pView);
202 : }
203 :
204 : /* Initialize the counter of the number of rows deleted, if
205 : ** we are counting rows.
206 : */
207 6 : if( db->flags & SQLITE_CountRows ){
208 0 : memCnt = pParse->nMem++;
209 0 : sqlite3VdbeAddOp(v, OP_MemInt, 0, memCnt);
210 : }
211 :
212 : /* Special case: A DELETE without a WHERE clause deletes everything.
213 : ** It is easier just to erase the whole table. Note, however, that
214 : ** this means that the row change count will be incorrect.
215 : */
216 7 : if( pWhere==0 && !triggers_exist && !IsVirtual(pTab) ){
217 1 : if( db->flags & SQLITE_CountRows ){
218 : /* If counting rows deleted, just count the total number of
219 : ** entries in the table. */
220 0 : int endOfLoop = sqlite3VdbeMakeLabel(v);
221 : int addr2;
222 0 : if( !isView ){
223 0 : sqlite3OpenTable(pParse, iCur, iDb, pTab, OP_OpenRead);
224 : }
225 0 : sqlite3VdbeAddOp(v, OP_Rewind, iCur, sqlite3VdbeCurrentAddr(v)+2);
226 0 : addr2 = sqlite3VdbeAddOp(v, OP_MemIncr, 1, memCnt);
227 0 : sqlite3VdbeAddOp(v, OP_Next, iCur, addr2);
228 0 : sqlite3VdbeResolveLabel(v, endOfLoop);
229 0 : sqlite3VdbeAddOp(v, OP_Close, iCur, 0);
230 : }
231 1 : if( !isView ){
232 1 : sqlite3VdbeAddOp(v, OP_Clear, pTab->tnum, iDb);
233 1 : if( !pParse->nested ){
234 1 : sqlite3VdbeChangeP3(v, -1, pTab->zName, P3_STATIC);
235 : }
236 2 : for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
237 : assert( pIdx->pSchema==pTab->pSchema );
238 1 : sqlite3VdbeAddOp(v, OP_Clear, pIdx->tnum, iDb);
239 : }
240 : }
241 : }
242 : /* The usual case: There is a WHERE clause so we have to scan through
243 : ** the table and pick which records to delete.
244 : */
245 : else{
246 : /* Begin the database scan
247 : */
248 5 : pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, 0);
249 5 : if( pWInfo==0 ) goto delete_from_cleanup;
250 :
251 : /* Remember the rowid of every item to be deleted.
252 : */
253 5 : sqlite3VdbeAddOp(v, IsVirtual(pTab) ? OP_VRowid : OP_Rowid, iCur, 0);
254 5 : sqlite3VdbeAddOp(v, OP_FifoWrite, 0, 0);
255 5 : if( db->flags & SQLITE_CountRows ){
256 0 : sqlite3VdbeAddOp(v, OP_MemIncr, 1, memCnt);
257 : }
258 :
259 : /* End the database scan loop.
260 : */
261 5 : sqlite3WhereEnd(pWInfo);
262 :
263 : /* Open the pseudo-table used to store OLD if there are triggers.
264 : */
265 5 : if( triggers_exist ){
266 0 : sqlite3VdbeAddOp(v, OP_OpenPseudo, oldIdx, 0);
267 0 : sqlite3VdbeAddOp(v, OP_SetNumColumns, oldIdx, pTab->nCol);
268 : }
269 :
270 : /* Delete every item whose key was written to the list during the
271 : ** database scan. We have to delete items after the scan is complete
272 : ** because deleting an item can change the scan order.
273 : */
274 5 : end = sqlite3VdbeMakeLabel(v);
275 :
276 : /* This is the beginning of the delete loop when there are
277 : ** row triggers.
278 : */
279 5 : if( triggers_exist ){
280 0 : addr = sqlite3VdbeAddOp(v, OP_FifoRead, 0, end);
281 0 : if( !isView ){
282 0 : sqlite3VdbeAddOp(v, OP_Dup, 0, 0);
283 0 : sqlite3OpenTable(pParse, iCur, iDb, pTab, OP_OpenRead);
284 : }
285 0 : sqlite3VdbeAddOp(v, OP_MoveGe, iCur, 0);
286 0 : sqlite3VdbeAddOp(v, OP_Rowid, iCur, 0);
287 0 : sqlite3VdbeAddOp(v, OP_RowData, iCur, 0);
288 0 : sqlite3VdbeAddOp(v, OP_Insert, oldIdx, 0);
289 0 : if( !isView ){
290 0 : sqlite3VdbeAddOp(v, OP_Close, iCur, 0);
291 : }
292 :
293 0 : (void)sqlite3CodeRowTrigger(pParse, TK_DELETE, 0, TRIGGER_BEFORE, pTab,
294 : -1, oldIdx, (pParse->trigStack)?pParse->trigStack->orconf:OE_Default,
295 : addr);
296 : }
297 :
298 5 : if( !isView ){
299 : /* Open cursors for the table we are deleting from and all its
300 : ** indices. If there are row triggers, this happens inside the
301 : ** OP_FifoRead loop because the cursor have to all be closed
302 : ** before the trigger fires. If there are no row triggers, the
303 : ** cursors are opened only once on the outside the loop.
304 : */
305 5 : sqlite3OpenTableAndIndices(pParse, pTab, iCur, OP_OpenWrite);
306 :
307 : /* This is the beginning of the delete loop when there are no
308 : ** row triggers */
309 5 : if( !triggers_exist ){
310 5 : addr = sqlite3VdbeAddOp(v, OP_FifoRead, 0, end);
311 : }
312 :
313 : /* Delete the row */
314 : #ifndef SQLITE_OMIT_VIRTUALTABLE
315 5 : if( IsVirtual(pTab) ){
316 0 : pParse->pVirtualLock = pTab;
317 0 : sqlite3VdbeOp3(v, OP_VUpdate, 0, 1, (const char*)pTab->pVtab, P3_VTAB);
318 : }else
319 : #endif
320 : {
321 5 : sqlite3GenerateRowDelete(db, v, pTab, iCur, pParse->nested==0);
322 : }
323 : }
324 :
325 : /* If there are row triggers, close all cursors then invoke
326 : ** the AFTER triggers
327 : */
328 5 : if( triggers_exist ){
329 0 : if( !isView ){
330 0 : for(i=1, pIdx=pTab->pIndex; pIdx; i++, pIdx=pIdx->pNext){
331 0 : sqlite3VdbeAddOp(v, OP_Close, iCur + i, pIdx->tnum);
332 : }
333 0 : sqlite3VdbeAddOp(v, OP_Close, iCur, 0);
334 : }
335 0 : (void)sqlite3CodeRowTrigger(pParse, TK_DELETE, 0, TRIGGER_AFTER, pTab, -1,
336 : oldIdx, (pParse->trigStack)?pParse->trigStack->orconf:OE_Default,
337 : addr);
338 : }
339 :
340 : /* End of the delete loop */
341 5 : sqlite3VdbeAddOp(v, OP_Goto, 0, addr);
342 5 : sqlite3VdbeResolveLabel(v, end);
343 :
344 : /* Close the cursors after the loop if there are no row triggers */
345 5 : if( !triggers_exist && !IsVirtual(pTab) ){
346 5 : for(i=1, pIdx=pTab->pIndex; pIdx; i++, pIdx=pIdx->pNext){
347 0 : sqlite3VdbeAddOp(v, OP_Close, iCur + i, pIdx->tnum);
348 : }
349 5 : sqlite3VdbeAddOp(v, OP_Close, iCur, 0);
350 : }
351 : }
352 :
353 : /*
354 : ** Return the number of rows that were deleted. If this routine is
355 : ** generating code because of a call to sqlite3NestedParse(), do not
356 : ** invoke the callback function.
357 : */
358 6 : if( db->flags & SQLITE_CountRows && pParse->nested==0 && !pParse->trigStack ){
359 0 : sqlite3VdbeAddOp(v, OP_MemLoad, memCnt, 0);
360 0 : sqlite3VdbeAddOp(v, OP_Callback, 1, 0);
361 0 : sqlite3VdbeSetNumCols(v, 1);
362 0 : sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "rows deleted", P3_STATIC);
363 : }
364 :
365 6 : delete_from_cleanup:
366 6 : sqlite3AuthContextPop(&sContext);
367 6 : sqlite3SrcListDelete(pTabList);
368 6 : sqlite3ExprDelete(pWhere);
369 : return;
370 : }
371 :
372 : /*
373 : ** This routine generates VDBE code that causes a single row of a
374 : ** single table to be deleted.
375 : **
376 : ** The VDBE must be in a particular state when this routine is called.
377 : ** These are the requirements:
378 : **
379 : ** 1. A read/write cursor pointing to pTab, the table containing the row
380 : ** to be deleted, must be opened as cursor number "base".
381 : **
382 : ** 2. Read/write cursors for all indices of pTab must be open as
383 : ** cursor number base+i for the i-th index.
384 : **
385 : ** 3. The record number of the row to be deleted must be on the top
386 : ** of the stack.
387 : **
388 : ** This routine pops the top of the stack to remove the record number
389 : ** and then generates code to remove both the table record and all index
390 : ** entries that point to that record.
391 : */
392 : void sqlite3GenerateRowDelete(
393 : sqlite3 *db, /* The database containing the index */
394 : Vdbe *v, /* Generate code into this VDBE */
395 : Table *pTab, /* Table containing the row to be deleted */
396 : int iCur, /* Cursor number for the table */
397 : int count /* Increment the row change counter */
398 5 : ){
399 : int addr;
400 5 : addr = sqlite3VdbeAddOp(v, OP_NotExists, iCur, 0);
401 5 : sqlite3GenerateRowIndexDelete(v, pTab, iCur, 0);
402 5 : sqlite3VdbeAddOp(v, OP_Delete, iCur, (count?OPFLAG_NCHANGE:0));
403 5 : if( count ){
404 0 : sqlite3VdbeChangeP3(v, -1, pTab->zName, P3_STATIC);
405 : }
406 5 : sqlite3VdbeJumpHere(v, addr);
407 5 : }
408 :
409 : /*
410 : ** This routine generates VDBE code that causes the deletion of all
411 : ** index entries associated with a single row of a single table.
412 : **
413 : ** The VDBE must be in a particular state when this routine is called.
414 : ** These are the requirements:
415 : **
416 : ** 1. A read/write cursor pointing to pTab, the table containing the row
417 : ** to be deleted, must be opened as cursor number "iCur".
418 : **
419 : ** 2. Read/write cursors for all indices of pTab must be open as
420 : ** cursor number iCur+i for the i-th index.
421 : **
422 : ** 3. The "iCur" cursor must be pointing to the row that is to be
423 : ** deleted.
424 : */
425 : void sqlite3GenerateRowIndexDelete(
426 : Vdbe *v, /* Generate code into this VDBE */
427 : Table *pTab, /* Table containing the row to be deleted */
428 : int iCur, /* Cursor number for the table */
429 : char *aIdxUsed /* Only delete if aIdxUsed!=0 && aIdxUsed[i]!=0 */
430 68 : ){
431 : int i;
432 : Index *pIdx;
433 :
434 68 : for(i=1, pIdx=pTab->pIndex; pIdx; i++, pIdx=pIdx->pNext){
435 0 : if( aIdxUsed!=0 && aIdxUsed[i-1]==0 ) continue;
436 0 : sqlite3GenerateIndexKey(v, pIdx, iCur);
437 0 : sqlite3VdbeAddOp(v, OP_IdxDelete, iCur+i, 0);
438 : }
439 68 : }
440 :
441 : /*
442 : ** Generate code that will assemble an index key and put it on the top
443 : ** of the tack. The key with be for index pIdx which is an index on pTab.
444 : ** iCur is the index of a cursor open on the pTab table and pointing to
445 : ** the entry that needs indexing.
446 : */
447 : void sqlite3GenerateIndexKey(
448 : Vdbe *v, /* Generate code into this VDBE */
449 : Index *pIdx, /* The index for which to generate a key */
450 : int iCur /* Cursor number for the pIdx->pTable table */
451 0 : ){
452 : int j;
453 0 : Table *pTab = pIdx->pTable;
454 :
455 0 : sqlite3VdbeAddOp(v, OP_Rowid, iCur, 0);
456 0 : for(j=0; j<pIdx->nColumn; j++){
457 0 : int idx = pIdx->aiColumn[j];
458 0 : if( idx==pTab->iPKey ){
459 0 : sqlite3VdbeAddOp(v, OP_Dup, j, 0);
460 : }else{
461 0 : sqlite3VdbeAddOp(v, OP_Column, iCur, idx);
462 0 : sqlite3ColumnDefault(v, pTab, idx);
463 : }
464 : }
465 0 : sqlite3VdbeAddOp(v, OP_MakeIdxRec, pIdx->nColumn, 0);
466 0 : sqlite3IndexAffinityStr(v, pIdx);
467 0 : }
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