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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: delete.c,v 1.129 2007/04/16 15:06:25 danielk1977 Exp $
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*/
24Table *sqlite3SrcListLookup(Parse *pParse, SrcList *pSrc){
25 Table *pTab = 0;
26 int i;
27 struct SrcList_item *pItem;
28 for(i=0, pItem=pSrc->a; i<pSrc->nSrc; i++, pItem++){
29 pTab = sqlite3LocateTable(pParse, pItem->zName, pItem->zDatabase);
30 sqlite3DeleteTable(pItem->pTab);
31 pItem->pTab = pTab;
32 if( pTab ){
33 pTab->nRef++;
34 }
35 }
36 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*/
44int sqlite3IsReadOnly(Parse *pParse, Table *pTab, int viewOk){
45 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 sqlite3ErrorMsg(pParse, "table %s may not be modified", pTab->zName);
52 return 1;
53 }
54#ifndef SQLITE_OMIT_VIEW
55 if( !viewOk && pTab->pSelect ){
56 sqlite3ErrorMsg(pParse,"cannot modify %s because it is a view",pTab->zName);
57 return 1;
58 }
59#endif
60 return 0;
61}
62
63/*
64** Generate code that will open a table for reading.
65*/
66void 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){
73 Vdbe *v;
74 if( IsVirtual(pTab) ) return;
75 v = sqlite3GetVdbe(p);
76 assert( opcode==OP_OpenWrite || opcode==OP_OpenRead );
77 sqlite3TableLock(p, iDb, pTab->tnum, (opcode==OP_OpenWrite), pTab->zName);
78 sqlite3VdbeAddOp(v, OP_Integer, iDb, 0);
79 VdbeComment((v, "# %s", pTab->zName));
80 sqlite3VdbeAddOp(v, opcode, iCur, pTab->tnum);
81 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*/
92void 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){
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 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 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 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 int triggers_exist = 0; /* True if any triggers exist */
115#endif
116
117 sContext.pParse = 0;
118 if( pParse->nErr || sqlite3MallocFailed() ){
119 goto delete_from_cleanup;
120 }
121 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 pTab = sqlite3SrcListLookup(pParse, pTabList);
130 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 triggers_exist = sqlite3TriggersExist(pParse, pTab, TK_DELETE, 0);
137 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 if( sqlite3IsReadOnly(pParse, pTab, triggers_exist) ){
148 goto delete_from_cleanup;
149 }
150 iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
151 assert( iDb<db->nDb );
152 zDb = db->aDb[iDb].zName;
153 if( sqlite3AuthCheck(pParse, SQLITE_DELETE, pTab->zName, 0, zDb) ){
154 goto delete_from_cleanup;
155 }
156
157 /* If pTab is really a view, make sure it has been initialized.
158 */
159 if( sqlite3ViewGetColumnNames(pParse, pTab) ){
160 goto delete_from_cleanup;
161 }
162
163 /* Allocate a cursor used to store the old.* data for a trigger.
164 */
165 if( triggers_exist ){
166 oldIdx = pParse->nTab++;
167 }
168
169 /* Resolve the column names in the WHERE clause.
170 */
171 assert( pTabList->nSrc==1 );
172 iCur = pTabList->a[0].iCursor = pParse->nTab++;
173 memset(&sNC, 0, sizeof(sNC));
174 sNC.pParse = pParse;
175 sNC.pSrcList = pTabList;
176 if( sqlite3ExprResolveNames(&sNC, pWhere) ){
177 goto delete_from_cleanup;
178 }
179
180 /* Start the view context
181 */
182 if( isView ){
183 sqlite3AuthContextPush(pParse, &sContext, pTab->zName);
184 }
185
186 /* Begin generating code.
187 */
188 v = sqlite3GetVdbe(pParse);
189 if( v==0 ){
190 goto delete_from_cleanup;
191 }
192 if( pParse->nested==0 ) sqlite3VdbeCountChanges(v);
193 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 if( isView ){
199 Select *pView = sqlite3SelectDup(pTab->pSelect);
200 sqlite3Select(pParse, pView, SRT_EphemTab, iCur, 0, 0, 0, 0);
201 sqlite3SelectDelete(pView);
202 }
203
204 /* Initialize the counter of the number of rows deleted, if
205 ** we are counting rows.
206 */
207 if( db->flags & SQLITE_CountRows ){
208 memCnt = pParse->nMem++;
209 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 if( pWhere==0 && !triggers_exist && !IsVirtual(pTab) ){
217 if( db->flags & SQLITE_CountRows ){
218 /* If counting rows deleted, just count the total number of
219 ** entries in the table. */
220 int endOfLoop = sqlite3VdbeMakeLabel(v);
221 int addr2;
222 if( !isView ){
223 sqlite3OpenTable(pParse, iCur, iDb, pTab, OP_OpenRead);
224 }
225 sqlite3VdbeAddOp(v, OP_Rewind, iCur, sqlite3VdbeCurrentAddr(v)+2);
226 addr2 = sqlite3VdbeAddOp(v, OP_MemIncr, 1, memCnt);
227 sqlite3VdbeAddOp(v, OP_Next, iCur, addr2);
228 sqlite3VdbeResolveLabel(v, endOfLoop);
229 sqlite3VdbeAddOp(v, OP_Close, iCur, 0);
230 }
231 if( !isView ){
232 sqlite3VdbeAddOp(v, OP_Clear, pTab->tnum, iDb);
233 if( !pParse->nested ){
234 sqlite3VdbeChangeP3(v, -1, pTab->zName, P3_STATIC);
235 }
236 for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
237 assert( pIdx->pSchema==pTab->pSchema );
238 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 pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, 0);
249 if( pWInfo==0 ) goto delete_from_cleanup;
250
251 /* Remember the rowid of every item to be deleted.
252 */
253 sqlite3VdbeAddOp(v, IsVirtual(pTab) ? OP_VRowid : OP_Rowid, iCur, 0);
254 sqlite3VdbeAddOp(v, OP_FifoWrite, 0, 0);
255 if( db->flags & SQLITE_CountRows ){
256 sqlite3VdbeAddOp(v, OP_MemIncr, 1, memCnt);
257 }
258
259 /* End the database scan loop.
260 */
261 sqlite3WhereEnd(pWInfo);
262
263 /* Open the pseudo-table used to store OLD if there are triggers.
264 */
265 if( triggers_exist ){
266 sqlite3VdbeAddOp(v, OP_OpenPseudo, oldIdx, 0);
267 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 end = sqlite3VdbeMakeLabel(v);
275
276 /* This is the beginning of the delete loop when there are
277 ** row triggers.
278 */
279 if( triggers_exist ){
280 addr = sqlite3VdbeAddOp(v, OP_FifoRead, 0, end);
281 if( !isView ){
282 sqlite3VdbeAddOp(v, OP_Dup, 0, 0);
283 sqlite3OpenTable(pParse, iCur, iDb, pTab, OP_OpenRead);
284 }
285 sqlite3VdbeAddOp(v, OP_MoveGe, iCur, 0);
286 sqlite3VdbeAddOp(v, OP_Rowid, iCur, 0);
287 sqlite3VdbeAddOp(v, OP_RowData, iCur, 0);
288 sqlite3VdbeAddOp(v, OP_Insert, oldIdx, 0);
289 if( !isView ){
290 sqlite3VdbeAddOp(v, OP_Close, iCur, 0);
291 }
292
293 (void)sqlite3CodeRowTrigger(pParse, TK_DELETE, 0, TRIGGER_BEFORE, pTab,
294 -1, oldIdx, (pParse->trigStack)?pParse->trigStack->orconf:OE_Default,
295 addr);
296 }
297
298 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 sqlite3OpenTableAndIndices(pParse, pTab, iCur, OP_OpenWrite);
306
307 /* This is the beginning of the delete loop when there are no
308 ** row triggers */
309 if( !triggers_exist ){
310 addr = sqlite3VdbeAddOp(v, OP_FifoRead, 0, end);
311 }
312
313 /* Delete the row */
314#ifndef SQLITE_OMIT_VIRTUALTABLE
315 if( IsVirtual(pTab) ){
316 pParse->pVirtualLock = pTab;
317 sqlite3VdbeOp3(v, OP_VUpdate, 0, 1, (const char*)pTab->pVtab, P3_VTAB);
318 }else
319#endif
320 {
321 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 if( triggers_exist ){
329 if( !isView ){
330 for(i=1, pIdx=pTab->pIndex; pIdx; i++, pIdx=pIdx->pNext){
331 sqlite3VdbeAddOp(v, OP_Close, iCur + i, pIdx->tnum);
332 }
333 sqlite3VdbeAddOp(v, OP_Close, iCur, 0);
334 }
335 (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 sqlite3VdbeAddOp(v, OP_Goto, 0, addr);
342 sqlite3VdbeResolveLabel(v, end);
343
344 /* Close the cursors after the loop if there are no row triggers */
345 if( !triggers_exist && !IsVirtual(pTab) ){
346 for(i=1, pIdx=pTab->pIndex; pIdx; i++, pIdx=pIdx->pNext){
347 sqlite3VdbeAddOp(v, OP_Close, iCur + i, pIdx->tnum);
348 }
349 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 if( db->flags & SQLITE_CountRows && pParse->nested==0 && !pParse->trigStack ){
359 sqlite3VdbeAddOp(v, OP_MemLoad, memCnt, 0);
360 sqlite3VdbeAddOp(v, OP_Callback, 1, 0);
361 sqlite3VdbeSetNumCols(v, 1);
362 sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "rows deleted", P3_STATIC);
363 }
364
365delete_from_cleanup:
366 sqlite3AuthContextPop(&sContext);
367 sqlite3SrcListDelete(pTabList);
368 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*/
392void 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){
399 int addr;
400 addr = sqlite3VdbeAddOp(v, OP_NotExists, iCur, 0);
401 sqlite3GenerateRowIndexDelete(v, pTab, iCur, 0);
402 sqlite3VdbeAddOp(v, OP_Delete, iCur, (count?OPFLAG_NCHANGE:0));
403 if( count ){
404 sqlite3VdbeChangeP3(v, -1, pTab->zName, P3_STATIC);
405 }
406 sqlite3VdbeJumpHere(v, addr);
407}
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*/
425void 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){
431 int i;
432 Index *pIdx;
433
434 for(i=1, pIdx=pTab->pIndex; pIdx; i++, pIdx=pIdx->pNext){
435 if( aIdxUsed!=0 && aIdxUsed[i-1]==0 ) continue;
436 sqlite3GenerateIndexKey(v, pIdx, iCur);
437 sqlite3VdbeAddOp(v, OP_IdxDelete, iCur+i, 0);
438 }
439}
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*/
447void 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){
452 int j;
453 Table *pTab = pIdx->pTable;
454
455 sqlite3VdbeAddOp(v, OP_Rowid, iCur, 0);
456 for(j=0; j<pIdx->nColumn; j++){
457 int idx = pIdx->aiColumn[j];
458 if( idx==pTab->iPKey ){
459 sqlite3VdbeAddOp(v, OP_Dup, j, 0);
460 }else{
461 sqlite3VdbeAddOp(v, OP_Column, iCur, idx);
462 sqlite3ColumnDefault(v, pTab, idx);
463 }
464 }
465 sqlite3VdbeAddOp(v, OP_MakeIdxRec, pIdx->nColumn, 0);
466 sqlite3IndexAffinityStr(v, pIdx);
467}

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