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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** to handle DELETE FROM statements.
14**
15** $Id: delete.c,v 1.1 2003/08/05 23:03:07 graydon 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 *sqliteSrcListLookup(Parse *pParse, SrcList *pSrc){
25 Table *pTab = 0;
26 int i;
27 for(i=0; i<pSrc->nSrc; i++){
28 const char *zTab = pSrc->a[i].zName;
29 const char *zDb = pSrc->a[i].zDatabase;
30 pTab = sqliteLocateTable(pParse, zTab, zDb);
31 pSrc->a[i].pTab = pTab;
32 }
33 return pTab;
34}
35
36/*
37** Check to make sure the given table is writable. If it is not
38** writable, generate an error message and return 1. If it is
39** writable return 0;
40*/
41int sqliteIsReadOnly(Parse *pParse, Table *pTab, int viewOk){
42 if( pTab->readOnly ){
43 sqliteErrorMsg(pParse, "table %s may not be modified", pTab->zName);
44 return 1;
45 }
46 if( !viewOk && pTab->pSelect ){
47 sqliteErrorMsg(pParse, "cannot modify %s because it is a view",pTab->zName);
48 return 1;
49 }
50 return 0;
51}
52
53/*
54** Process a DELETE FROM statement.
55*/
56void sqliteDeleteFrom(
57 Parse *pParse, /* The parser context */
58 SrcList *pTabList, /* The table from which we should delete things */
59 Expr *pWhere /* The WHERE clause. May be null */
60){
61 Vdbe *v; /* The virtual database engine */
62 Table *pTab; /* The table from which records will be deleted */
63 const char *zDb; /* Name of database holding pTab */
64 int end, addr; /* A couple addresses of generated code */
65 int i; /* Loop counter */
66 WhereInfo *pWInfo; /* Information about the WHERE clause */
67 Index *pIdx; /* For looping over indices of the table */
68 int iCur; /* VDBE Cursor number for pTab */
69 sqlite *db; /* Main database structure */
70 int isView; /* True if attempting to delete from a view */
71 AuthContext sContext; /* Authorization context */
72
73 int row_triggers_exist = 0; /* True if any triggers exist */
74 int before_triggers; /* True if there are BEFORE triggers */
75 int after_triggers; /* True if there are AFTER triggers */
76 int oldIdx = -1; /* Cursor for the OLD table of AFTER triggers */
77
78 sContext.pParse = 0;
79 if( pParse->nErr || sqlite_malloc_failed ){
80 pTabList = 0;
81 goto delete_from_cleanup;
82 }
83 db = pParse->db;
84 assert( pTabList->nSrc==1 );
85
86 /* Locate the table which we want to delete. This table has to be
87 ** put in an SrcList structure because some of the subroutines we
88 ** will be calling are designed to work with multiple tables and expect
89 ** an SrcList* parameter instead of just a Table* parameter.
90 */
91 pTab = sqliteSrcListLookup(pParse, pTabList);
92 if( pTab==0 ) goto delete_from_cleanup;
93 before_triggers = sqliteTriggersExist(pParse, pTab->pTrigger,
94 TK_DELETE, TK_BEFORE, TK_ROW, 0);
95 after_triggers = sqliteTriggersExist(pParse, pTab->pTrigger,
96 TK_DELETE, TK_AFTER, TK_ROW, 0);
97 row_triggers_exist = before_triggers || after_triggers;
98 isView = pTab->pSelect!=0;
99 if( sqliteIsReadOnly(pParse, pTab, before_triggers) ){
100 goto delete_from_cleanup;
101 }
102 assert( pTab->iDb<db->nDb );
103 zDb = db->aDb[pTab->iDb].zName;
104 if( sqliteAuthCheck(pParse, SQLITE_DELETE, pTab->zName, 0, zDb) ){
105 goto delete_from_cleanup;
106 }
107
108 /* If pTab is really a view, make sure it has been initialized.
109 */
110 if( isView && sqliteViewGetColumnNames(pParse, pTab) ){
111 goto delete_from_cleanup;
112 }
113
114 /* Allocate a cursor used to store the old.* data for a trigger.
115 */
116 if( row_triggers_exist ){
117 oldIdx = pParse->nTab++;
118 }
119
120 /* Resolve the column names in all the expressions.
121 */
122 assert( pTabList->nSrc==1 );
123 iCur = pTabList->a[0].iCursor = pParse->nTab++;
124 if( pWhere ){
125 if( sqliteExprResolveIds(pParse, pTabList, 0, pWhere) ){
126 goto delete_from_cleanup;
127 }
128 if( sqliteExprCheck(pParse, pWhere, 0, 0) ){
129 goto delete_from_cleanup;
130 }
131 }
132
133 /* Start the view context
134 */
135 if( isView ){
136 sqliteAuthContextPush(pParse, &sContext, pTab->zName);
137 }
138
139 /* Begin generating code.
140 */
141 v = sqliteGetVdbe(pParse);
142 if( v==0 ){
143 goto delete_from_cleanup;
144 }
145 sqliteBeginWriteOperation(pParse, row_triggers_exist, pTab->iDb);
146
147 /* If we are trying to delete from a view, construct that view into
148 ** a temporary table.
149 */
150 if( isView ){
151 Select *pView = sqliteSelectDup(pTab->pSelect);
152 sqliteSelect(pParse, pView, SRT_TempTable, iCur, 0, 0, 0);
153 sqliteSelectDelete(pView);
154 }
155
156 /* Initialize the counter of the number of rows deleted, if
157 ** we are counting rows.
158 */
159 if( db->flags & SQLITE_CountRows ){
160 sqliteVdbeAddOp(v, OP_Integer, 0, 0);
161 }
162
163 /* Special case: A DELETE without a WHERE clause deletes everything.
164 ** It is easier just to erase the whole table. Note, however, that
165 ** this means that the row change count will be incorrect.
166 */
167 if( pWhere==0 && !row_triggers_exist ){
168 if( db->flags & SQLITE_CountRows ){
169 /* If counting rows deleted, just count the total number of
170 ** entries in the table. */
171 int endOfLoop = sqliteVdbeMakeLabel(v);
172 int addr;
173 if( !isView ){
174 sqliteVdbeAddOp(v, OP_Integer, pTab->iDb, 0);
175 sqliteVdbeAddOp(v, OP_OpenRead, iCur, pTab->tnum);
176 }
177 sqliteVdbeAddOp(v, OP_Rewind, iCur, sqliteVdbeCurrentAddr(v)+2);
178 addr = sqliteVdbeAddOp(v, OP_AddImm, 1, 0);
179 sqliteVdbeAddOp(v, OP_Next, iCur, addr);
180 sqliteVdbeResolveLabel(v, endOfLoop);
181 sqliteVdbeAddOp(v, OP_Close, iCur, 0);
182 }
183 if( !isView ){
184 sqliteVdbeAddOp(v, OP_Clear, pTab->tnum, pTab->iDb);
185 for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
186 sqliteVdbeAddOp(v, OP_Clear, pIdx->tnum, pIdx->iDb);
187 }
188 }
189 }
190
191 /* The usual case: There is a WHERE clause so we have to scan through
192 ** the table an pick which records to delete.
193 */
194 else{
195 /* Begin the database scan
196 */
197 pWInfo = sqliteWhereBegin(pParse, pTabList, pWhere, 1, 0);
198 if( pWInfo==0 ) goto delete_from_cleanup;
199
200 /* Remember the key of every item to be deleted.
201 */
202 sqliteVdbeAddOp(v, OP_ListWrite, 0, 0);
203 if( db->flags & SQLITE_CountRows ){
204 sqliteVdbeAddOp(v, OP_AddImm, 1, 0);
205 }
206
207 /* End the database scan loop.
208 */
209 sqliteWhereEnd(pWInfo);
210
211 /* Open the pseudo-table used to store OLD if there are triggers.
212 */
213 if( row_triggers_exist ){
214 sqliteVdbeAddOp(v, OP_OpenPseudo, oldIdx, 0);
215 }
216
217 /* Delete every item whose key was written to the list during the
218 ** database scan. We have to delete items after the scan is complete
219 ** because deleting an item can change the scan order.
220 */
221 sqliteVdbeAddOp(v, OP_ListRewind, 0, 0);
222 end = sqliteVdbeMakeLabel(v);
223
224 /* This is the beginning of the delete loop when there are
225 ** row triggers.
226 */
227 if( row_triggers_exist ){
228 addr = sqliteVdbeAddOp(v, OP_ListRead, 0, end);
229 sqliteVdbeAddOp(v, OP_Dup, 0, 0);
230 if( !isView ){
231 sqliteVdbeAddOp(v, OP_Integer, pTab->iDb, 0);
232 sqliteVdbeAddOp(v, OP_OpenRead, iCur, pTab->tnum);
233 }
234 sqliteVdbeAddOp(v, OP_MoveTo, iCur, 0);
235
236 sqliteVdbeAddOp(v, OP_Recno, iCur, 0);
237 sqliteVdbeAddOp(v, OP_RowData, iCur, 0);
238 sqliteVdbeAddOp(v, OP_PutIntKey, oldIdx, 0);
239 if( !isView ){
240 sqliteVdbeAddOp(v, OP_Close, iCur, 0);
241 }
242
243 sqliteCodeRowTrigger(pParse, TK_DELETE, 0, TK_BEFORE, pTab, -1,
244 oldIdx, (pParse->trigStack)?pParse->trigStack->orconf:OE_Default,
245 addr);
246 }
247
248 if( !isView ){
249 /* Open cursors for the table we are deleting from and all its
250 ** indices. If there are row triggers, this happens inside the
251 ** OP_ListRead loop because the cursor have to all be closed
252 ** before the trigger fires. If there are no row triggers, the
253 ** cursors are opened only once on the outside the loop.
254 */
255 pParse->nTab = iCur + 1;
256 sqliteVdbeAddOp(v, OP_Integer, pTab->iDb, 0);
257 sqliteVdbeAddOp(v, OP_OpenWrite, iCur, pTab->tnum);
258 for(i=1, pIdx=pTab->pIndex; pIdx; i++, pIdx=pIdx->pNext){
259 sqliteVdbeAddOp(v, OP_Integer, pIdx->iDb, 0);
260 sqliteVdbeAddOp(v, OP_OpenWrite, pParse->nTab++, pIdx->tnum);
261 }
262
263 /* This is the beginning of the delete loop when there are no
264 ** row triggers */
265 if( !row_triggers_exist ){
266 addr = sqliteVdbeAddOp(v, OP_ListRead, 0, end);
267 }
268
269 /* Delete the row */
270 sqliteGenerateRowDelete(db, v, pTab, iCur, pParse->trigStack==0);
271 }
272
273 /* If there are row triggers, close all cursors then invoke
274 ** the AFTER triggers
275 */
276 if( row_triggers_exist ){
277 if( !isView ){
278 for(i=1, pIdx=pTab->pIndex; pIdx; i++, pIdx=pIdx->pNext){
279 sqliteVdbeAddOp(v, OP_Close, iCur + i, pIdx->tnum);
280 }
281 sqliteVdbeAddOp(v, OP_Close, iCur, 0);
282 }
283 sqliteCodeRowTrigger(pParse, TK_DELETE, 0, TK_AFTER, pTab, -1,
284 oldIdx, (pParse->trigStack)?pParse->trigStack->orconf:OE_Default,
285 addr);
286 }
287
288 /* End of the delete loop */
289 sqliteVdbeAddOp(v, OP_Goto, 0, addr);
290 sqliteVdbeResolveLabel(v, end);
291 sqliteVdbeAddOp(v, OP_ListReset, 0, 0);
292
293 /* Close the cursors after the loop if there are no row triggers */
294 if( !row_triggers_exist ){
295 for(i=1, pIdx=pTab->pIndex; pIdx; i++, pIdx=pIdx->pNext){
296 sqliteVdbeAddOp(v, OP_Close, iCur + i, pIdx->tnum);
297 }
298 sqliteVdbeAddOp(v, OP_Close, iCur, 0);
299 pParse->nTab = iCur;
300 }
301 }
302 sqliteEndWriteOperation(pParse);
303
304 /*
305 ** Return the number of rows that were deleted.
306 */
307 if( db->flags & SQLITE_CountRows ){
308 sqliteVdbeAddOp(v, OP_ColumnName, 0, 0);
309 sqliteVdbeChangeP3(v, -1, "rows deleted", P3_STATIC);
310 sqliteVdbeAddOp(v, OP_Callback, 1, 0);
311 }
312
313delete_from_cleanup:
314 sqliteAuthContextPop(&sContext);
315 sqliteSrcListDelete(pTabList);
316 sqliteExprDelete(pWhere);
317 return;
318}
319
320/*
321** This routine generates VDBE code that causes a single row of a
322** single table to be deleted.
323**
324** The VDBE must be in a particular state when this routine is called.
325** These are the requirements:
326**
327** 1. A read/write cursor pointing to pTab, the table containing the row
328** to be deleted, must be opened as cursor number "base".
329**
330** 2. Read/write cursors for all indices of pTab must be open as
331** cursor number base+i for the i-th index.
332**
333** 3. The record number of the row to be deleted must be on the top
334** of the stack.
335**
336** This routine pops the top of the stack to remove the record number
337** and then generates code to remove both the table record and all index
338** entries that point to that record.
339*/
340void sqliteGenerateRowDelete(
341 sqlite *db, /* The database containing the index */
342 Vdbe *v, /* Generate code into this VDBE */
343 Table *pTab, /* Table containing the row to be deleted */
344 int iCur, /* Cursor number for the table */
345 int count /* Increment the row change counter */
346){
347 int addr;
348 addr = sqliteVdbeAddOp(v, OP_NotExists, iCur, 0);
349 sqliteGenerateRowIndexDelete(db, v, pTab, iCur, 0);
350 sqliteVdbeAddOp(v, OP_Delete, iCur, count);
351 sqliteVdbeChangeP2(v, addr, sqliteVdbeCurrentAddr(v));
352}
353
354/*
355** This routine generates VDBE code that causes the deletion of all
356** index entries associated with a single row of a single table.
357**
358** The VDBE must be in a particular state when this routine is called.
359** These are the requirements:
360**
361** 1. A read/write cursor pointing to pTab, the table containing the row
362** to be deleted, must be opened as cursor number "iCur".
363**
364** 2. Read/write cursors for all indices of pTab must be open as
365** cursor number iCur+i for the i-th index.
366**
367** 3. The "iCur" cursor must be pointing to the row that is to be
368** deleted.
369*/
370void sqliteGenerateRowIndexDelete(
371 sqlite *db, /* The database containing the index */
372 Vdbe *v, /* Generate code into this VDBE */
373 Table *pTab, /* Table containing the row to be deleted */
374 int iCur, /* Cursor number for the table */
375 char *aIdxUsed /* Only delete if aIdxUsed!=0 && aIdxUsed[i]!=0 */
376){
377 int i;
378 Index *pIdx;
379
380 for(i=1, pIdx=pTab->pIndex; pIdx; i++, pIdx=pIdx->pNext){
381 int j;
382 if( aIdxUsed!=0 && aIdxUsed[i-1]==0 ) continue;
383 sqliteVdbeAddOp(v, OP_Recno, iCur, 0);
384 for(j=0; j<pIdx->nColumn; j++){
385 int idx = pIdx->aiColumn[j];
386 if( idx==pTab->iPKey ){
387 sqliteVdbeAddOp(v, OP_Dup, j, 0);
388 }else{
389 sqliteVdbeAddOp(v, OP_Column, iCur, idx);
390 }
391 }
392 sqliteVdbeAddOp(v, OP_MakeIdxKey, pIdx->nColumn, 0);
393 if( db->file_format>=4 ) sqliteAddIdxKeyType(v, pIdx);
394 sqliteVdbeAddOp(v, OP_IdxDelete, iCur+i, 0);
395 }
396}

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