Annotation of embedaddon/sqlite3/src/fkey.c, revision 1.1.1.1
1.1 misho 1: /*
2: **
3: ** The author disclaims copyright to this source code. In place of
4: ** a legal notice, here is a blessing:
5: **
6: ** May you do good and not evil.
7: ** May you find forgiveness for yourself and forgive others.
8: ** May you share freely, never taking more than you give.
9: **
10: *************************************************************************
11: ** This file contains code used by the compiler to add foreign key
12: ** support to compiled SQL statements.
13: */
14: #include "sqliteInt.h"
15:
16: #ifndef SQLITE_OMIT_FOREIGN_KEY
17: #ifndef SQLITE_OMIT_TRIGGER
18:
19: /*
20: ** Deferred and Immediate FKs
21: ** --------------------------
22: **
23: ** Foreign keys in SQLite come in two flavours: deferred and immediate.
24: ** If an immediate foreign key constraint is violated, SQLITE_CONSTRAINT
25: ** is returned and the current statement transaction rolled back. If a
26: ** deferred foreign key constraint is violated, no action is taken
27: ** immediately. However if the application attempts to commit the
28: ** transaction before fixing the constraint violation, the attempt fails.
29: **
30: ** Deferred constraints are implemented using a simple counter associated
31: ** with the database handle. The counter is set to zero each time a
32: ** database transaction is opened. Each time a statement is executed
33: ** that causes a foreign key violation, the counter is incremented. Each
34: ** time a statement is executed that removes an existing violation from
35: ** the database, the counter is decremented. When the transaction is
36: ** committed, the commit fails if the current value of the counter is
37: ** greater than zero. This scheme has two big drawbacks:
38: **
39: ** * When a commit fails due to a deferred foreign key constraint,
40: ** there is no way to tell which foreign constraint is not satisfied,
41: ** or which row it is not satisfied for.
42: **
43: ** * If the database contains foreign key violations when the
44: ** transaction is opened, this may cause the mechanism to malfunction.
45: **
46: ** Despite these problems, this approach is adopted as it seems simpler
47: ** than the alternatives.
48: **
49: ** INSERT operations:
50: **
51: ** I.1) For each FK for which the table is the child table, search
52: ** the parent table for a match. If none is found increment the
53: ** constraint counter.
54: **
55: ** I.2) For each FK for which the table is the parent table,
56: ** search the child table for rows that correspond to the new
57: ** row in the parent table. Decrement the counter for each row
58: ** found (as the constraint is now satisfied).
59: **
60: ** DELETE operations:
61: **
62: ** D.1) For each FK for which the table is the child table,
63: ** search the parent table for a row that corresponds to the
64: ** deleted row in the child table. If such a row is not found,
65: ** decrement the counter.
66: **
67: ** D.2) For each FK for which the table is the parent table, search
68: ** the child table for rows that correspond to the deleted row
69: ** in the parent table. For each found increment the counter.
70: **
71: ** UPDATE operations:
72: **
73: ** An UPDATE command requires that all 4 steps above are taken, but only
74: ** for FK constraints for which the affected columns are actually
75: ** modified (values must be compared at runtime).
76: **
77: ** Note that I.1 and D.1 are very similar operations, as are I.2 and D.2.
78: ** This simplifies the implementation a bit.
79: **
80: ** For the purposes of immediate FK constraints, the OR REPLACE conflict
81: ** resolution is considered to delete rows before the new row is inserted.
82: ** If a delete caused by OR REPLACE violates an FK constraint, an exception
83: ** is thrown, even if the FK constraint would be satisfied after the new
84: ** row is inserted.
85: **
86: ** Immediate constraints are usually handled similarly. The only difference
87: ** is that the counter used is stored as part of each individual statement
88: ** object (struct Vdbe). If, after the statement has run, its immediate
89: ** constraint counter is greater than zero, it returns SQLITE_CONSTRAINT
90: ** and the statement transaction is rolled back. An exception is an INSERT
91: ** statement that inserts a single row only (no triggers). In this case,
92: ** instead of using a counter, an exception is thrown immediately if the
93: ** INSERT violates a foreign key constraint. This is necessary as such
94: ** an INSERT does not open a statement transaction.
95: **
96: ** TODO: How should dropping a table be handled? How should renaming a
97: ** table be handled?
98: **
99: **
100: ** Query API Notes
101: ** ---------------
102: **
103: ** Before coding an UPDATE or DELETE row operation, the code-generator
104: ** for those two operations needs to know whether or not the operation
105: ** requires any FK processing and, if so, which columns of the original
106: ** row are required by the FK processing VDBE code (i.e. if FKs were
107: ** implemented using triggers, which of the old.* columns would be
108: ** accessed). No information is required by the code-generator before
109: ** coding an INSERT operation. The functions used by the UPDATE/DELETE
110: ** generation code to query for this information are:
111: **
112: ** sqlite3FkRequired() - Test to see if FK processing is required.
113: ** sqlite3FkOldmask() - Query for the set of required old.* columns.
114: **
115: **
116: ** Externally accessible module functions
117: ** --------------------------------------
118: **
119: ** sqlite3FkCheck() - Check for foreign key violations.
120: ** sqlite3FkActions() - Code triggers for ON UPDATE/ON DELETE actions.
121: ** sqlite3FkDelete() - Delete an FKey structure.
122: */
123:
124: /*
125: ** VDBE Calling Convention
126: ** -----------------------
127: **
128: ** Example:
129: **
130: ** For the following INSERT statement:
131: **
132: ** CREATE TABLE t1(a, b INTEGER PRIMARY KEY, c);
133: ** INSERT INTO t1 VALUES(1, 2, 3.1);
134: **
135: ** Register (x): 2 (type integer)
136: ** Register (x+1): 1 (type integer)
137: ** Register (x+2): NULL (type NULL)
138: ** Register (x+3): 3.1 (type real)
139: */
140:
141: /*
142: ** A foreign key constraint requires that the key columns in the parent
143: ** table are collectively subject to a UNIQUE or PRIMARY KEY constraint.
144: ** Given that pParent is the parent table for foreign key constraint pFKey,
145: ** search the schema a unique index on the parent key columns.
146: **
147: ** If successful, zero is returned. If the parent key is an INTEGER PRIMARY
148: ** KEY column, then output variable *ppIdx is set to NULL. Otherwise, *ppIdx
149: ** is set to point to the unique index.
150: **
151: ** If the parent key consists of a single column (the foreign key constraint
152: ** is not a composite foreign key), output variable *paiCol is set to NULL.
153: ** Otherwise, it is set to point to an allocated array of size N, where
154: ** N is the number of columns in the parent key. The first element of the
155: ** array is the index of the child table column that is mapped by the FK
156: ** constraint to the parent table column stored in the left-most column
157: ** of index *ppIdx. The second element of the array is the index of the
158: ** child table column that corresponds to the second left-most column of
159: ** *ppIdx, and so on.
160: **
161: ** If the required index cannot be found, either because:
162: **
163: ** 1) The named parent key columns do not exist, or
164: **
165: ** 2) The named parent key columns do exist, but are not subject to a
166: ** UNIQUE or PRIMARY KEY constraint, or
167: **
168: ** 3) No parent key columns were provided explicitly as part of the
169: ** foreign key definition, and the parent table does not have a
170: ** PRIMARY KEY, or
171: **
172: ** 4) No parent key columns were provided explicitly as part of the
173: ** foreign key definition, and the PRIMARY KEY of the parent table
174: ** consists of a a different number of columns to the child key in
175: ** the child table.
176: **
177: ** then non-zero is returned, and a "foreign key mismatch" error loaded
178: ** into pParse. If an OOM error occurs, non-zero is returned and the
179: ** pParse->db->mallocFailed flag is set.
180: */
181: static int locateFkeyIndex(
182: Parse *pParse, /* Parse context to store any error in */
183: Table *pParent, /* Parent table of FK constraint pFKey */
184: FKey *pFKey, /* Foreign key to find index for */
185: Index **ppIdx, /* OUT: Unique index on parent table */
186: int **paiCol /* OUT: Map of index columns in pFKey */
187: ){
188: Index *pIdx = 0; /* Value to return via *ppIdx */
189: int *aiCol = 0; /* Value to return via *paiCol */
190: int nCol = pFKey->nCol; /* Number of columns in parent key */
191: char *zKey = pFKey->aCol[0].zCol; /* Name of left-most parent key column */
192:
193: /* The caller is responsible for zeroing output parameters. */
194: assert( ppIdx && *ppIdx==0 );
195: assert( !paiCol || *paiCol==0 );
196: assert( pParse );
197:
198: /* If this is a non-composite (single column) foreign key, check if it
199: ** maps to the INTEGER PRIMARY KEY of table pParent. If so, leave *ppIdx
200: ** and *paiCol set to zero and return early.
201: **
202: ** Otherwise, for a composite foreign key (more than one column), allocate
203: ** space for the aiCol array (returned via output parameter *paiCol).
204: ** Non-composite foreign keys do not require the aiCol array.
205: */
206: if( nCol==1 ){
207: /* The FK maps to the IPK if any of the following are true:
208: **
209: ** 1) There is an INTEGER PRIMARY KEY column and the FK is implicitly
210: ** mapped to the primary key of table pParent, or
211: ** 2) The FK is explicitly mapped to a column declared as INTEGER
212: ** PRIMARY KEY.
213: */
214: if( pParent->iPKey>=0 ){
215: if( !zKey ) return 0;
216: if( !sqlite3StrICmp(pParent->aCol[pParent->iPKey].zName, zKey) ) return 0;
217: }
218: }else if( paiCol ){
219: assert( nCol>1 );
220: aiCol = (int *)sqlite3DbMallocRaw(pParse->db, nCol*sizeof(int));
221: if( !aiCol ) return 1;
222: *paiCol = aiCol;
223: }
224:
225: for(pIdx=pParent->pIndex; pIdx; pIdx=pIdx->pNext){
226: if( pIdx->nColumn==nCol && pIdx->onError!=OE_None ){
227: /* pIdx is a UNIQUE index (or a PRIMARY KEY) and has the right number
228: ** of columns. If each indexed column corresponds to a foreign key
229: ** column of pFKey, then this index is a winner. */
230:
231: if( zKey==0 ){
232: /* If zKey is NULL, then this foreign key is implicitly mapped to
233: ** the PRIMARY KEY of table pParent. The PRIMARY KEY index may be
234: ** identified by the test (Index.autoIndex==2). */
235: if( pIdx->autoIndex==2 ){
236: if( aiCol ){
237: int i;
238: for(i=0; i<nCol; i++) aiCol[i] = pFKey->aCol[i].iFrom;
239: }
240: break;
241: }
242: }else{
243: /* If zKey is non-NULL, then this foreign key was declared to
244: ** map to an explicit list of columns in table pParent. Check if this
245: ** index matches those columns. Also, check that the index uses
246: ** the default collation sequences for each column. */
247: int i, j;
248: for(i=0; i<nCol; i++){
249: int iCol = pIdx->aiColumn[i]; /* Index of column in parent tbl */
250: char *zDfltColl; /* Def. collation for column */
251: char *zIdxCol; /* Name of indexed column */
252:
253: /* If the index uses a collation sequence that is different from
254: ** the default collation sequence for the column, this index is
255: ** unusable. Bail out early in this case. */
256: zDfltColl = pParent->aCol[iCol].zColl;
257: if( !zDfltColl ){
258: zDfltColl = "BINARY";
259: }
260: if( sqlite3StrICmp(pIdx->azColl[i], zDfltColl) ) break;
261:
262: zIdxCol = pParent->aCol[iCol].zName;
263: for(j=0; j<nCol; j++){
264: if( sqlite3StrICmp(pFKey->aCol[j].zCol, zIdxCol)==0 ){
265: if( aiCol ) aiCol[i] = pFKey->aCol[j].iFrom;
266: break;
267: }
268: }
269: if( j==nCol ) break;
270: }
271: if( i==nCol ) break; /* pIdx is usable */
272: }
273: }
274: }
275:
276: if( !pIdx ){
277: if( !pParse->disableTriggers ){
278: sqlite3ErrorMsg(pParse, "foreign key mismatch");
279: }
280: sqlite3DbFree(pParse->db, aiCol);
281: return 1;
282: }
283:
284: *ppIdx = pIdx;
285: return 0;
286: }
287:
288: /*
289: ** This function is called when a row is inserted into or deleted from the
290: ** child table of foreign key constraint pFKey. If an SQL UPDATE is executed
291: ** on the child table of pFKey, this function is invoked twice for each row
292: ** affected - once to "delete" the old row, and then again to "insert" the
293: ** new row.
294: **
295: ** Each time it is called, this function generates VDBE code to locate the
296: ** row in the parent table that corresponds to the row being inserted into
297: ** or deleted from the child table. If the parent row can be found, no
298: ** special action is taken. Otherwise, if the parent row can *not* be
299: ** found in the parent table:
300: **
301: ** Operation | FK type | Action taken
302: ** --------------------------------------------------------------------------
303: ** INSERT immediate Increment the "immediate constraint counter".
304: **
305: ** DELETE immediate Decrement the "immediate constraint counter".
306: **
307: ** INSERT deferred Increment the "deferred constraint counter".
308: **
309: ** DELETE deferred Decrement the "deferred constraint counter".
310: **
311: ** These operations are identified in the comment at the top of this file
312: ** (fkey.c) as "I.1" and "D.1".
313: */
314: static void fkLookupParent(
315: Parse *pParse, /* Parse context */
316: int iDb, /* Index of database housing pTab */
317: Table *pTab, /* Parent table of FK pFKey */
318: Index *pIdx, /* Unique index on parent key columns in pTab */
319: FKey *pFKey, /* Foreign key constraint */
320: int *aiCol, /* Map from parent key columns to child table columns */
321: int regData, /* Address of array containing child table row */
322: int nIncr, /* Increment constraint counter by this */
323: int isIgnore /* If true, pretend pTab contains all NULL values */
324: ){
325: int i; /* Iterator variable */
326: Vdbe *v = sqlite3GetVdbe(pParse); /* Vdbe to add code to */
327: int iCur = pParse->nTab - 1; /* Cursor number to use */
328: int iOk = sqlite3VdbeMakeLabel(v); /* jump here if parent key found */
329:
330: /* If nIncr is less than zero, then check at runtime if there are any
331: ** outstanding constraints to resolve. If there are not, there is no need
332: ** to check if deleting this row resolves any outstanding violations.
333: **
334: ** Check if any of the key columns in the child table row are NULL. If
335: ** any are, then the constraint is considered satisfied. No need to
336: ** search for a matching row in the parent table. */
337: if( nIncr<0 ){
338: sqlite3VdbeAddOp2(v, OP_FkIfZero, pFKey->isDeferred, iOk);
339: }
340: for(i=0; i<pFKey->nCol; i++){
341: int iReg = aiCol[i] + regData + 1;
342: sqlite3VdbeAddOp2(v, OP_IsNull, iReg, iOk);
343: }
344:
345: if( isIgnore==0 ){
346: if( pIdx==0 ){
347: /* If pIdx is NULL, then the parent key is the INTEGER PRIMARY KEY
348: ** column of the parent table (table pTab). */
349: int iMustBeInt; /* Address of MustBeInt instruction */
350: int regTemp = sqlite3GetTempReg(pParse);
351:
352: /* Invoke MustBeInt to coerce the child key value to an integer (i.e.
353: ** apply the affinity of the parent key). If this fails, then there
354: ** is no matching parent key. Before using MustBeInt, make a copy of
355: ** the value. Otherwise, the value inserted into the child key column
356: ** will have INTEGER affinity applied to it, which may not be correct. */
357: sqlite3VdbeAddOp2(v, OP_SCopy, aiCol[0]+1+regData, regTemp);
358: iMustBeInt = sqlite3VdbeAddOp2(v, OP_MustBeInt, regTemp, 0);
359:
360: /* If the parent table is the same as the child table, and we are about
361: ** to increment the constraint-counter (i.e. this is an INSERT operation),
362: ** then check if the row being inserted matches itself. If so, do not
363: ** increment the constraint-counter. */
364: if( pTab==pFKey->pFrom && nIncr==1 ){
365: sqlite3VdbeAddOp3(v, OP_Eq, regData, iOk, regTemp);
366: }
367:
368: sqlite3OpenTable(pParse, iCur, iDb, pTab, OP_OpenRead);
369: sqlite3VdbeAddOp3(v, OP_NotExists, iCur, 0, regTemp);
370: sqlite3VdbeAddOp2(v, OP_Goto, 0, iOk);
371: sqlite3VdbeJumpHere(v, sqlite3VdbeCurrentAddr(v)-2);
372: sqlite3VdbeJumpHere(v, iMustBeInt);
373: sqlite3ReleaseTempReg(pParse, regTemp);
374: }else{
375: int nCol = pFKey->nCol;
376: int regTemp = sqlite3GetTempRange(pParse, nCol);
377: int regRec = sqlite3GetTempReg(pParse);
378: KeyInfo *pKey = sqlite3IndexKeyinfo(pParse, pIdx);
379:
380: sqlite3VdbeAddOp3(v, OP_OpenRead, iCur, pIdx->tnum, iDb);
381: sqlite3VdbeChangeP4(v, -1, (char*)pKey, P4_KEYINFO_HANDOFF);
382: for(i=0; i<nCol; i++){
383: sqlite3VdbeAddOp2(v, OP_Copy, aiCol[i]+1+regData, regTemp+i);
384: }
385:
386: /* If the parent table is the same as the child table, and we are about
387: ** to increment the constraint-counter (i.e. this is an INSERT operation),
388: ** then check if the row being inserted matches itself. If so, do not
389: ** increment the constraint-counter.
390: **
391: ** If any of the parent-key values are NULL, then the row cannot match
392: ** itself. So set JUMPIFNULL to make sure we do the OP_Found if any
393: ** of the parent-key values are NULL (at this point it is known that
394: ** none of the child key values are).
395: */
396: if( pTab==pFKey->pFrom && nIncr==1 ){
397: int iJump = sqlite3VdbeCurrentAddr(v) + nCol + 1;
398: for(i=0; i<nCol; i++){
399: int iChild = aiCol[i]+1+regData;
400: int iParent = pIdx->aiColumn[i]+1+regData;
401: assert( aiCol[i]!=pTab->iPKey );
402: if( pIdx->aiColumn[i]==pTab->iPKey ){
403: /* The parent key is a composite key that includes the IPK column */
404: iParent = regData;
405: }
406: sqlite3VdbeAddOp3(v, OP_Ne, iChild, iJump, iParent);
407: sqlite3VdbeChangeP5(v, SQLITE_JUMPIFNULL);
408: }
409: sqlite3VdbeAddOp2(v, OP_Goto, 0, iOk);
410: }
411:
412: sqlite3VdbeAddOp3(v, OP_MakeRecord, regTemp, nCol, regRec);
413: sqlite3VdbeChangeP4(v, -1, sqlite3IndexAffinityStr(v,pIdx), P4_TRANSIENT);
414: sqlite3VdbeAddOp4Int(v, OP_Found, iCur, iOk, regRec, 0);
415:
416: sqlite3ReleaseTempReg(pParse, regRec);
417: sqlite3ReleaseTempRange(pParse, regTemp, nCol);
418: }
419: }
420:
421: if( !pFKey->isDeferred && !pParse->pToplevel && !pParse->isMultiWrite ){
422: /* Special case: If this is an INSERT statement that will insert exactly
423: ** one row into the table, raise a constraint immediately instead of
424: ** incrementing a counter. This is necessary as the VM code is being
425: ** generated for will not open a statement transaction. */
426: assert( nIncr==1 );
427: sqlite3HaltConstraint(
428: pParse, OE_Abort, "foreign key constraint failed", P4_STATIC
429: );
430: }else{
431: if( nIncr>0 && pFKey->isDeferred==0 ){
432: sqlite3ParseToplevel(pParse)->mayAbort = 1;
433: }
434: sqlite3VdbeAddOp2(v, OP_FkCounter, pFKey->isDeferred, nIncr);
435: }
436:
437: sqlite3VdbeResolveLabel(v, iOk);
438: sqlite3VdbeAddOp1(v, OP_Close, iCur);
439: }
440:
441: /*
442: ** This function is called to generate code executed when a row is deleted
443: ** from the parent table of foreign key constraint pFKey and, if pFKey is
444: ** deferred, when a row is inserted into the same table. When generating
445: ** code for an SQL UPDATE operation, this function may be called twice -
446: ** once to "delete" the old row and once to "insert" the new row.
447: **
448: ** The code generated by this function scans through the rows in the child
449: ** table that correspond to the parent table row being deleted or inserted.
450: ** For each child row found, one of the following actions is taken:
451: **
452: ** Operation | FK type | Action taken
453: ** --------------------------------------------------------------------------
454: ** DELETE immediate Increment the "immediate constraint counter".
455: ** Or, if the ON (UPDATE|DELETE) action is RESTRICT,
456: ** throw a "foreign key constraint failed" exception.
457: **
458: ** INSERT immediate Decrement the "immediate constraint counter".
459: **
460: ** DELETE deferred Increment the "deferred constraint counter".
461: ** Or, if the ON (UPDATE|DELETE) action is RESTRICT,
462: ** throw a "foreign key constraint failed" exception.
463: **
464: ** INSERT deferred Decrement the "deferred constraint counter".
465: **
466: ** These operations are identified in the comment at the top of this file
467: ** (fkey.c) as "I.2" and "D.2".
468: */
469: static void fkScanChildren(
470: Parse *pParse, /* Parse context */
471: SrcList *pSrc, /* SrcList containing the table to scan */
472: Table *pTab,
473: Index *pIdx, /* Foreign key index */
474: FKey *pFKey, /* Foreign key relationship */
475: int *aiCol, /* Map from pIdx cols to child table cols */
476: int regData, /* Referenced table data starts here */
477: int nIncr /* Amount to increment deferred counter by */
478: ){
479: sqlite3 *db = pParse->db; /* Database handle */
480: int i; /* Iterator variable */
481: Expr *pWhere = 0; /* WHERE clause to scan with */
482: NameContext sNameContext; /* Context used to resolve WHERE clause */
483: WhereInfo *pWInfo; /* Context used by sqlite3WhereXXX() */
484: int iFkIfZero = 0; /* Address of OP_FkIfZero */
485: Vdbe *v = sqlite3GetVdbe(pParse);
486:
487: assert( !pIdx || pIdx->pTable==pTab );
488:
489: if( nIncr<0 ){
490: iFkIfZero = sqlite3VdbeAddOp2(v, OP_FkIfZero, pFKey->isDeferred, 0);
491: }
492:
493: /* Create an Expr object representing an SQL expression like:
494: **
495: ** <parent-key1> = <child-key1> AND <parent-key2> = <child-key2> ...
496: **
497: ** The collation sequence used for the comparison should be that of
498: ** the parent key columns. The affinity of the parent key column should
499: ** be applied to each child key value before the comparison takes place.
500: */
501: for(i=0; i<pFKey->nCol; i++){
502: Expr *pLeft; /* Value from parent table row */
503: Expr *pRight; /* Column ref to child table */
504: Expr *pEq; /* Expression (pLeft = pRight) */
505: int iCol; /* Index of column in child table */
506: const char *zCol; /* Name of column in child table */
507:
508: pLeft = sqlite3Expr(db, TK_REGISTER, 0);
509: if( pLeft ){
510: /* Set the collation sequence and affinity of the LHS of each TK_EQ
511: ** expression to the parent key column defaults. */
512: if( pIdx ){
513: Column *pCol;
514: iCol = pIdx->aiColumn[i];
515: pCol = &pTab->aCol[iCol];
516: if( pTab->iPKey==iCol ) iCol = -1;
517: pLeft->iTable = regData+iCol+1;
518: pLeft->affinity = pCol->affinity;
519: pLeft->pColl = sqlite3LocateCollSeq(pParse, pCol->zColl);
520: }else{
521: pLeft->iTable = regData;
522: pLeft->affinity = SQLITE_AFF_INTEGER;
523: }
524: }
525: iCol = aiCol ? aiCol[i] : pFKey->aCol[0].iFrom;
526: assert( iCol>=0 );
527: zCol = pFKey->pFrom->aCol[iCol].zName;
528: pRight = sqlite3Expr(db, TK_ID, zCol);
529: pEq = sqlite3PExpr(pParse, TK_EQ, pLeft, pRight, 0);
530: pWhere = sqlite3ExprAnd(db, pWhere, pEq);
531: }
532:
533: /* If the child table is the same as the parent table, and this scan
534: ** is taking place as part of a DELETE operation (operation D.2), omit the
535: ** row being deleted from the scan by adding ($rowid != rowid) to the WHERE
536: ** clause, where $rowid is the rowid of the row being deleted. */
537: if( pTab==pFKey->pFrom && nIncr>0 ){
538: Expr *pEq; /* Expression (pLeft = pRight) */
539: Expr *pLeft; /* Value from parent table row */
540: Expr *pRight; /* Column ref to child table */
541: pLeft = sqlite3Expr(db, TK_REGISTER, 0);
542: pRight = sqlite3Expr(db, TK_COLUMN, 0);
543: if( pLeft && pRight ){
544: pLeft->iTable = regData;
545: pLeft->affinity = SQLITE_AFF_INTEGER;
546: pRight->iTable = pSrc->a[0].iCursor;
547: pRight->iColumn = -1;
548: }
549: pEq = sqlite3PExpr(pParse, TK_NE, pLeft, pRight, 0);
550: pWhere = sqlite3ExprAnd(db, pWhere, pEq);
551: }
552:
553: /* Resolve the references in the WHERE clause. */
554: memset(&sNameContext, 0, sizeof(NameContext));
555: sNameContext.pSrcList = pSrc;
556: sNameContext.pParse = pParse;
557: sqlite3ResolveExprNames(&sNameContext, pWhere);
558:
559: /* Create VDBE to loop through the entries in pSrc that match the WHERE
560: ** clause. If the constraint is not deferred, throw an exception for
561: ** each row found. Otherwise, for deferred constraints, increment the
562: ** deferred constraint counter by nIncr for each row selected. */
563: pWInfo = sqlite3WhereBegin(pParse, pSrc, pWhere, 0, 0, 0);
564: if( nIncr>0 && pFKey->isDeferred==0 ){
565: sqlite3ParseToplevel(pParse)->mayAbort = 1;
566: }
567: sqlite3VdbeAddOp2(v, OP_FkCounter, pFKey->isDeferred, nIncr);
568: if( pWInfo ){
569: sqlite3WhereEnd(pWInfo);
570: }
571:
572: /* Clean up the WHERE clause constructed above. */
573: sqlite3ExprDelete(db, pWhere);
574: if( iFkIfZero ){
575: sqlite3VdbeJumpHere(v, iFkIfZero);
576: }
577: }
578:
579: /*
580: ** This function returns a pointer to the head of a linked list of FK
581: ** constraints for which table pTab is the parent table. For example,
582: ** given the following schema:
583: **
584: ** CREATE TABLE t1(a PRIMARY KEY);
585: ** CREATE TABLE t2(b REFERENCES t1(a);
586: **
587: ** Calling this function with table "t1" as an argument returns a pointer
588: ** to the FKey structure representing the foreign key constraint on table
589: ** "t2". Calling this function with "t2" as the argument would return a
590: ** NULL pointer (as there are no FK constraints for which t2 is the parent
591: ** table).
592: */
593: FKey *sqlite3FkReferences(Table *pTab){
594: int nName = sqlite3Strlen30(pTab->zName);
595: return (FKey *)sqlite3HashFind(&pTab->pSchema->fkeyHash, pTab->zName, nName);
596: }
597:
598: /*
599: ** The second argument is a Trigger structure allocated by the
600: ** fkActionTrigger() routine. This function deletes the Trigger structure
601: ** and all of its sub-components.
602: **
603: ** The Trigger structure or any of its sub-components may be allocated from
604: ** the lookaside buffer belonging to database handle dbMem.
605: */
606: static void fkTriggerDelete(sqlite3 *dbMem, Trigger *p){
607: if( p ){
608: TriggerStep *pStep = p->step_list;
609: sqlite3ExprDelete(dbMem, pStep->pWhere);
610: sqlite3ExprListDelete(dbMem, pStep->pExprList);
611: sqlite3SelectDelete(dbMem, pStep->pSelect);
612: sqlite3ExprDelete(dbMem, p->pWhen);
613: sqlite3DbFree(dbMem, p);
614: }
615: }
616:
617: /*
618: ** This function is called to generate code that runs when table pTab is
619: ** being dropped from the database. The SrcList passed as the second argument
620: ** to this function contains a single entry guaranteed to resolve to
621: ** table pTab.
622: **
623: ** Normally, no code is required. However, if either
624: **
625: ** (a) The table is the parent table of a FK constraint, or
626: ** (b) The table is the child table of a deferred FK constraint and it is
627: ** determined at runtime that there are outstanding deferred FK
628: ** constraint violations in the database,
629: **
630: ** then the equivalent of "DELETE FROM <tbl>" is executed before dropping
631: ** the table from the database. Triggers are disabled while running this
632: ** DELETE, but foreign key actions are not.
633: */
634: void sqlite3FkDropTable(Parse *pParse, SrcList *pName, Table *pTab){
635: sqlite3 *db = pParse->db;
636: if( (db->flags&SQLITE_ForeignKeys) && !IsVirtual(pTab) && !pTab->pSelect ){
637: int iSkip = 0;
638: Vdbe *v = sqlite3GetVdbe(pParse);
639:
640: assert( v ); /* VDBE has already been allocated */
641: if( sqlite3FkReferences(pTab)==0 ){
642: /* Search for a deferred foreign key constraint for which this table
643: ** is the child table. If one cannot be found, return without
644: ** generating any VDBE code. If one can be found, then jump over
645: ** the entire DELETE if there are no outstanding deferred constraints
646: ** when this statement is run. */
647: FKey *p;
648: for(p=pTab->pFKey; p; p=p->pNextFrom){
649: if( p->isDeferred ) break;
650: }
651: if( !p ) return;
652: iSkip = sqlite3VdbeMakeLabel(v);
653: sqlite3VdbeAddOp2(v, OP_FkIfZero, 1, iSkip);
654: }
655:
656: pParse->disableTriggers = 1;
657: sqlite3DeleteFrom(pParse, sqlite3SrcListDup(db, pName, 0), 0);
658: pParse->disableTriggers = 0;
659:
660: /* If the DELETE has generated immediate foreign key constraint
661: ** violations, halt the VDBE and return an error at this point, before
662: ** any modifications to the schema are made. This is because statement
663: ** transactions are not able to rollback schema changes. */
664: sqlite3VdbeAddOp2(v, OP_FkIfZero, 0, sqlite3VdbeCurrentAddr(v)+2);
665: sqlite3HaltConstraint(
666: pParse, OE_Abort, "foreign key constraint failed", P4_STATIC
667: );
668:
669: if( iSkip ){
670: sqlite3VdbeResolveLabel(v, iSkip);
671: }
672: }
673: }
674:
675: /*
676: ** This function is called when inserting, deleting or updating a row of
677: ** table pTab to generate VDBE code to perform foreign key constraint
678: ** processing for the operation.
679: **
680: ** For a DELETE operation, parameter regOld is passed the index of the
681: ** first register in an array of (pTab->nCol+1) registers containing the
682: ** rowid of the row being deleted, followed by each of the column values
683: ** of the row being deleted, from left to right. Parameter regNew is passed
684: ** zero in this case.
685: **
686: ** For an INSERT operation, regOld is passed zero and regNew is passed the
687: ** first register of an array of (pTab->nCol+1) registers containing the new
688: ** row data.
689: **
690: ** For an UPDATE operation, this function is called twice. Once before
691: ** the original record is deleted from the table using the calling convention
692: ** described for DELETE. Then again after the original record is deleted
693: ** but before the new record is inserted using the INSERT convention.
694: */
695: void sqlite3FkCheck(
696: Parse *pParse, /* Parse context */
697: Table *pTab, /* Row is being deleted from this table */
698: int regOld, /* Previous row data is stored here */
699: int regNew /* New row data is stored here */
700: ){
701: sqlite3 *db = pParse->db; /* Database handle */
702: FKey *pFKey; /* Used to iterate through FKs */
703: int iDb; /* Index of database containing pTab */
704: const char *zDb; /* Name of database containing pTab */
705: int isIgnoreErrors = pParse->disableTriggers;
706:
707: /* Exactly one of regOld and regNew should be non-zero. */
708: assert( (regOld==0)!=(regNew==0) );
709:
710: /* If foreign-keys are disabled, this function is a no-op. */
711: if( (db->flags&SQLITE_ForeignKeys)==0 ) return;
712:
713: iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
714: zDb = db->aDb[iDb].zName;
715:
716: /* Loop through all the foreign key constraints for which pTab is the
717: ** child table (the table that the foreign key definition is part of). */
718: for(pFKey=pTab->pFKey; pFKey; pFKey=pFKey->pNextFrom){
719: Table *pTo; /* Parent table of foreign key pFKey */
720: Index *pIdx = 0; /* Index on key columns in pTo */
721: int *aiFree = 0;
722: int *aiCol;
723: int iCol;
724: int i;
725: int isIgnore = 0;
726:
727: /* Find the parent table of this foreign key. Also find a unique index
728: ** on the parent key columns in the parent table. If either of these
729: ** schema items cannot be located, set an error in pParse and return
730: ** early. */
731: if( pParse->disableTriggers ){
732: pTo = sqlite3FindTable(db, pFKey->zTo, zDb);
733: }else{
734: pTo = sqlite3LocateTable(pParse, 0, pFKey->zTo, zDb);
735: }
736: if( !pTo || locateFkeyIndex(pParse, pTo, pFKey, &pIdx, &aiFree) ){
737: assert( isIgnoreErrors==0 || (regOld!=0 && regNew==0) );
738: if( !isIgnoreErrors || db->mallocFailed ) return;
739: if( pTo==0 ){
740: /* If isIgnoreErrors is true, then a table is being dropped. In this
741: ** case SQLite runs a "DELETE FROM xxx" on the table being dropped
742: ** before actually dropping it in order to check FK constraints.
743: ** If the parent table of an FK constraint on the current table is
744: ** missing, behave as if it is empty. i.e. decrement the relevant
745: ** FK counter for each row of the current table with non-NULL keys.
746: */
747: Vdbe *v = sqlite3GetVdbe(pParse);
748: int iJump = sqlite3VdbeCurrentAddr(v) + pFKey->nCol + 1;
749: for(i=0; i<pFKey->nCol; i++){
750: int iReg = pFKey->aCol[i].iFrom + regOld + 1;
751: sqlite3VdbeAddOp2(v, OP_IsNull, iReg, iJump);
752: }
753: sqlite3VdbeAddOp2(v, OP_FkCounter, pFKey->isDeferred, -1);
754: }
755: continue;
756: }
757: assert( pFKey->nCol==1 || (aiFree && pIdx) );
758:
759: if( aiFree ){
760: aiCol = aiFree;
761: }else{
762: iCol = pFKey->aCol[0].iFrom;
763: aiCol = &iCol;
764: }
765: for(i=0; i<pFKey->nCol; i++){
766: if( aiCol[i]==pTab->iPKey ){
767: aiCol[i] = -1;
768: }
769: #ifndef SQLITE_OMIT_AUTHORIZATION
770: /* Request permission to read the parent key columns. If the
771: ** authorization callback returns SQLITE_IGNORE, behave as if any
772: ** values read from the parent table are NULL. */
773: if( db->xAuth ){
774: int rcauth;
775: char *zCol = pTo->aCol[pIdx ? pIdx->aiColumn[i] : pTo->iPKey].zName;
776: rcauth = sqlite3AuthReadCol(pParse, pTo->zName, zCol, iDb);
777: isIgnore = (rcauth==SQLITE_IGNORE);
778: }
779: #endif
780: }
781:
782: /* Take a shared-cache advisory read-lock on the parent table. Allocate
783: ** a cursor to use to search the unique index on the parent key columns
784: ** in the parent table. */
785: sqlite3TableLock(pParse, iDb, pTo->tnum, 0, pTo->zName);
786: pParse->nTab++;
787:
788: if( regOld!=0 ){
789: /* A row is being removed from the child table. Search for the parent.
790: ** If the parent does not exist, removing the child row resolves an
791: ** outstanding foreign key constraint violation. */
792: fkLookupParent(pParse, iDb, pTo, pIdx, pFKey, aiCol, regOld, -1,isIgnore);
793: }
794: if( regNew!=0 ){
795: /* A row is being added to the child table. If a parent row cannot
796: ** be found, adding the child row has violated the FK constraint. */
797: fkLookupParent(pParse, iDb, pTo, pIdx, pFKey, aiCol, regNew, +1,isIgnore);
798: }
799:
800: sqlite3DbFree(db, aiFree);
801: }
802:
803: /* Loop through all the foreign key constraints that refer to this table */
804: for(pFKey = sqlite3FkReferences(pTab); pFKey; pFKey=pFKey->pNextTo){
805: Index *pIdx = 0; /* Foreign key index for pFKey */
806: SrcList *pSrc;
807: int *aiCol = 0;
808:
809: if( !pFKey->isDeferred && !pParse->pToplevel && !pParse->isMultiWrite ){
810: assert( regOld==0 && regNew!=0 );
811: /* Inserting a single row into a parent table cannot cause an immediate
812: ** foreign key violation. So do nothing in this case. */
813: continue;
814: }
815:
816: if( locateFkeyIndex(pParse, pTab, pFKey, &pIdx, &aiCol) ){
817: if( !isIgnoreErrors || db->mallocFailed ) return;
818: continue;
819: }
820: assert( aiCol || pFKey->nCol==1 );
821:
822: /* Create a SrcList structure containing a single table (the table
823: ** the foreign key that refers to this table is attached to). This
824: ** is required for the sqlite3WhereXXX() interface. */
825: pSrc = sqlite3SrcListAppend(db, 0, 0, 0);
826: if( pSrc ){
827: struct SrcList_item *pItem = pSrc->a;
828: pItem->pTab = pFKey->pFrom;
829: pItem->zName = pFKey->pFrom->zName;
830: pItem->pTab->nRef++;
831: pItem->iCursor = pParse->nTab++;
832:
833: if( regNew!=0 ){
834: fkScanChildren(pParse, pSrc, pTab, pIdx, pFKey, aiCol, regNew, -1);
835: }
836: if( regOld!=0 ){
837: /* If there is a RESTRICT action configured for the current operation
838: ** on the parent table of this FK, then throw an exception
839: ** immediately if the FK constraint is violated, even if this is a
840: ** deferred trigger. That's what RESTRICT means. To defer checking
841: ** the constraint, the FK should specify NO ACTION (represented
842: ** using OE_None). NO ACTION is the default. */
843: fkScanChildren(pParse, pSrc, pTab, pIdx, pFKey, aiCol, regOld, 1);
844: }
845: pItem->zName = 0;
846: sqlite3SrcListDelete(db, pSrc);
847: }
848: sqlite3DbFree(db, aiCol);
849: }
850: }
851:
852: #define COLUMN_MASK(x) (((x)>31) ? 0xffffffff : ((u32)1<<(x)))
853:
854: /*
855: ** This function is called before generating code to update or delete a
856: ** row contained in table pTab.
857: */
858: u32 sqlite3FkOldmask(
859: Parse *pParse, /* Parse context */
860: Table *pTab /* Table being modified */
861: ){
862: u32 mask = 0;
863: if( pParse->db->flags&SQLITE_ForeignKeys ){
864: FKey *p;
865: int i;
866: for(p=pTab->pFKey; p; p=p->pNextFrom){
867: for(i=0; i<p->nCol; i++) mask |= COLUMN_MASK(p->aCol[i].iFrom);
868: }
869: for(p=sqlite3FkReferences(pTab); p; p=p->pNextTo){
870: Index *pIdx = 0;
871: locateFkeyIndex(pParse, pTab, p, &pIdx, 0);
872: if( pIdx ){
873: for(i=0; i<pIdx->nColumn; i++) mask |= COLUMN_MASK(pIdx->aiColumn[i]);
874: }
875: }
876: }
877: return mask;
878: }
879:
880: /*
881: ** This function is called before generating code to update or delete a
882: ** row contained in table pTab. If the operation is a DELETE, then
883: ** parameter aChange is passed a NULL value. For an UPDATE, aChange points
884: ** to an array of size N, where N is the number of columns in table pTab.
885: ** If the i'th column is not modified by the UPDATE, then the corresponding
886: ** entry in the aChange[] array is set to -1. If the column is modified,
887: ** the value is 0 or greater. Parameter chngRowid is set to true if the
888: ** UPDATE statement modifies the rowid fields of the table.
889: **
890: ** If any foreign key processing will be required, this function returns
891: ** true. If there is no foreign key related processing, this function
892: ** returns false.
893: */
894: int sqlite3FkRequired(
895: Parse *pParse, /* Parse context */
896: Table *pTab, /* Table being modified */
897: int *aChange, /* Non-NULL for UPDATE operations */
898: int chngRowid /* True for UPDATE that affects rowid */
899: ){
900: if( pParse->db->flags&SQLITE_ForeignKeys ){
901: if( !aChange ){
902: /* A DELETE operation. Foreign key processing is required if the
903: ** table in question is either the child or parent table for any
904: ** foreign key constraint. */
905: return (sqlite3FkReferences(pTab) || pTab->pFKey);
906: }else{
907: /* This is an UPDATE. Foreign key processing is only required if the
908: ** operation modifies one or more child or parent key columns. */
909: int i;
910: FKey *p;
911:
912: /* Check if any child key columns are being modified. */
913: for(p=pTab->pFKey; p; p=p->pNextFrom){
914: for(i=0; i<p->nCol; i++){
915: int iChildKey = p->aCol[i].iFrom;
916: if( aChange[iChildKey]>=0 ) return 1;
917: if( iChildKey==pTab->iPKey && chngRowid ) return 1;
918: }
919: }
920:
921: /* Check if any parent key columns are being modified. */
922: for(p=sqlite3FkReferences(pTab); p; p=p->pNextTo){
923: for(i=0; i<p->nCol; i++){
924: char *zKey = p->aCol[i].zCol;
925: int iKey;
926: for(iKey=0; iKey<pTab->nCol; iKey++){
927: Column *pCol = &pTab->aCol[iKey];
928: if( (zKey ? !sqlite3StrICmp(pCol->zName, zKey) : pCol->isPrimKey) ){
929: if( aChange[iKey]>=0 ) return 1;
930: if( iKey==pTab->iPKey && chngRowid ) return 1;
931: }
932: }
933: }
934: }
935: }
936: }
937: return 0;
938: }
939:
940: /*
941: ** This function is called when an UPDATE or DELETE operation is being
942: ** compiled on table pTab, which is the parent table of foreign-key pFKey.
943: ** If the current operation is an UPDATE, then the pChanges parameter is
944: ** passed a pointer to the list of columns being modified. If it is a
945: ** DELETE, pChanges is passed a NULL pointer.
946: **
947: ** It returns a pointer to a Trigger structure containing a trigger
948: ** equivalent to the ON UPDATE or ON DELETE action specified by pFKey.
949: ** If the action is "NO ACTION" or "RESTRICT", then a NULL pointer is
950: ** returned (these actions require no special handling by the triggers
951: ** sub-system, code for them is created by fkScanChildren()).
952: **
953: ** For example, if pFKey is the foreign key and pTab is table "p" in
954: ** the following schema:
955: **
956: ** CREATE TABLE p(pk PRIMARY KEY);
957: ** CREATE TABLE c(ck REFERENCES p ON DELETE CASCADE);
958: **
959: ** then the returned trigger structure is equivalent to:
960: **
961: ** CREATE TRIGGER ... DELETE ON p BEGIN
962: ** DELETE FROM c WHERE ck = old.pk;
963: ** END;
964: **
965: ** The returned pointer is cached as part of the foreign key object. It
966: ** is eventually freed along with the rest of the foreign key object by
967: ** sqlite3FkDelete().
968: */
969: static Trigger *fkActionTrigger(
970: Parse *pParse, /* Parse context */
971: Table *pTab, /* Table being updated or deleted from */
972: FKey *pFKey, /* Foreign key to get action for */
973: ExprList *pChanges /* Change-list for UPDATE, NULL for DELETE */
974: ){
975: sqlite3 *db = pParse->db; /* Database handle */
976: int action; /* One of OE_None, OE_Cascade etc. */
977: Trigger *pTrigger; /* Trigger definition to return */
978: int iAction = (pChanges!=0); /* 1 for UPDATE, 0 for DELETE */
979:
980: action = pFKey->aAction[iAction];
981: pTrigger = pFKey->apTrigger[iAction];
982:
983: if( action!=OE_None && !pTrigger ){
984: u8 enableLookaside; /* Copy of db->lookaside.bEnabled */
985: char const *zFrom; /* Name of child table */
986: int nFrom; /* Length in bytes of zFrom */
987: Index *pIdx = 0; /* Parent key index for this FK */
988: int *aiCol = 0; /* child table cols -> parent key cols */
989: TriggerStep *pStep = 0; /* First (only) step of trigger program */
990: Expr *pWhere = 0; /* WHERE clause of trigger step */
991: ExprList *pList = 0; /* Changes list if ON UPDATE CASCADE */
992: Select *pSelect = 0; /* If RESTRICT, "SELECT RAISE(...)" */
993: int i; /* Iterator variable */
994: Expr *pWhen = 0; /* WHEN clause for the trigger */
995:
996: if( locateFkeyIndex(pParse, pTab, pFKey, &pIdx, &aiCol) ) return 0;
997: assert( aiCol || pFKey->nCol==1 );
998:
999: for(i=0; i<pFKey->nCol; i++){
1000: Token tOld = { "old", 3 }; /* Literal "old" token */
1001: Token tNew = { "new", 3 }; /* Literal "new" token */
1002: Token tFromCol; /* Name of column in child table */
1003: Token tToCol; /* Name of column in parent table */
1004: int iFromCol; /* Idx of column in child table */
1005: Expr *pEq; /* tFromCol = OLD.tToCol */
1006:
1007: iFromCol = aiCol ? aiCol[i] : pFKey->aCol[0].iFrom;
1008: assert( iFromCol>=0 );
1009: tToCol.z = pIdx ? pTab->aCol[pIdx->aiColumn[i]].zName : "oid";
1010: tFromCol.z = pFKey->pFrom->aCol[iFromCol].zName;
1011:
1012: tToCol.n = sqlite3Strlen30(tToCol.z);
1013: tFromCol.n = sqlite3Strlen30(tFromCol.z);
1014:
1015: /* Create the expression "OLD.zToCol = zFromCol". It is important
1016: ** that the "OLD.zToCol" term is on the LHS of the = operator, so
1017: ** that the affinity and collation sequence associated with the
1018: ** parent table are used for the comparison. */
1019: pEq = sqlite3PExpr(pParse, TK_EQ,
1020: sqlite3PExpr(pParse, TK_DOT,
1021: sqlite3PExpr(pParse, TK_ID, 0, 0, &tOld),
1022: sqlite3PExpr(pParse, TK_ID, 0, 0, &tToCol)
1023: , 0),
1024: sqlite3PExpr(pParse, TK_ID, 0, 0, &tFromCol)
1025: , 0);
1026: pWhere = sqlite3ExprAnd(db, pWhere, pEq);
1027:
1028: /* For ON UPDATE, construct the next term of the WHEN clause.
1029: ** The final WHEN clause will be like this:
1030: **
1031: ** WHEN NOT(old.col1 IS new.col1 AND ... AND old.colN IS new.colN)
1032: */
1033: if( pChanges ){
1034: pEq = sqlite3PExpr(pParse, TK_IS,
1035: sqlite3PExpr(pParse, TK_DOT,
1036: sqlite3PExpr(pParse, TK_ID, 0, 0, &tOld),
1037: sqlite3PExpr(pParse, TK_ID, 0, 0, &tToCol),
1038: 0),
1039: sqlite3PExpr(pParse, TK_DOT,
1040: sqlite3PExpr(pParse, TK_ID, 0, 0, &tNew),
1041: sqlite3PExpr(pParse, TK_ID, 0, 0, &tToCol),
1042: 0),
1043: 0);
1044: pWhen = sqlite3ExprAnd(db, pWhen, pEq);
1045: }
1046:
1047: if( action!=OE_Restrict && (action!=OE_Cascade || pChanges) ){
1048: Expr *pNew;
1049: if( action==OE_Cascade ){
1050: pNew = sqlite3PExpr(pParse, TK_DOT,
1051: sqlite3PExpr(pParse, TK_ID, 0, 0, &tNew),
1052: sqlite3PExpr(pParse, TK_ID, 0, 0, &tToCol)
1053: , 0);
1054: }else if( action==OE_SetDflt ){
1055: Expr *pDflt = pFKey->pFrom->aCol[iFromCol].pDflt;
1056: if( pDflt ){
1057: pNew = sqlite3ExprDup(db, pDflt, 0);
1058: }else{
1059: pNew = sqlite3PExpr(pParse, TK_NULL, 0, 0, 0);
1060: }
1061: }else{
1062: pNew = sqlite3PExpr(pParse, TK_NULL, 0, 0, 0);
1063: }
1064: pList = sqlite3ExprListAppend(pParse, pList, pNew);
1065: sqlite3ExprListSetName(pParse, pList, &tFromCol, 0);
1066: }
1067: }
1068: sqlite3DbFree(db, aiCol);
1069:
1070: zFrom = pFKey->pFrom->zName;
1071: nFrom = sqlite3Strlen30(zFrom);
1072:
1073: if( action==OE_Restrict ){
1074: Token tFrom;
1075: Expr *pRaise;
1076:
1077: tFrom.z = zFrom;
1078: tFrom.n = nFrom;
1079: pRaise = sqlite3Expr(db, TK_RAISE, "foreign key constraint failed");
1080: if( pRaise ){
1081: pRaise->affinity = OE_Abort;
1082: }
1083: pSelect = sqlite3SelectNew(pParse,
1084: sqlite3ExprListAppend(pParse, 0, pRaise),
1085: sqlite3SrcListAppend(db, 0, &tFrom, 0),
1086: pWhere,
1087: 0, 0, 0, 0, 0, 0
1088: );
1089: pWhere = 0;
1090: }
1091:
1092: /* Disable lookaside memory allocation */
1093: enableLookaside = db->lookaside.bEnabled;
1094: db->lookaside.bEnabled = 0;
1095:
1096: pTrigger = (Trigger *)sqlite3DbMallocZero(db,
1097: sizeof(Trigger) + /* struct Trigger */
1098: sizeof(TriggerStep) + /* Single step in trigger program */
1099: nFrom + 1 /* Space for pStep->target.z */
1100: );
1101: if( pTrigger ){
1102: pStep = pTrigger->step_list = (TriggerStep *)&pTrigger[1];
1103: pStep->target.z = (char *)&pStep[1];
1104: pStep->target.n = nFrom;
1105: memcpy((char *)pStep->target.z, zFrom, nFrom);
1106:
1107: pStep->pWhere = sqlite3ExprDup(db, pWhere, EXPRDUP_REDUCE);
1108: pStep->pExprList = sqlite3ExprListDup(db, pList, EXPRDUP_REDUCE);
1109: pStep->pSelect = sqlite3SelectDup(db, pSelect, EXPRDUP_REDUCE);
1110: if( pWhen ){
1111: pWhen = sqlite3PExpr(pParse, TK_NOT, pWhen, 0, 0);
1112: pTrigger->pWhen = sqlite3ExprDup(db, pWhen, EXPRDUP_REDUCE);
1113: }
1114: }
1115:
1116: /* Re-enable the lookaside buffer, if it was disabled earlier. */
1117: db->lookaside.bEnabled = enableLookaside;
1118:
1119: sqlite3ExprDelete(db, pWhere);
1120: sqlite3ExprDelete(db, pWhen);
1121: sqlite3ExprListDelete(db, pList);
1122: sqlite3SelectDelete(db, pSelect);
1123: if( db->mallocFailed==1 ){
1124: fkTriggerDelete(db, pTrigger);
1125: return 0;
1126: }
1127: assert( pStep!=0 );
1128:
1129: switch( action ){
1130: case OE_Restrict:
1131: pStep->op = TK_SELECT;
1132: break;
1133: case OE_Cascade:
1134: if( !pChanges ){
1135: pStep->op = TK_DELETE;
1136: break;
1137: }
1138: default:
1139: pStep->op = TK_UPDATE;
1140: }
1141: pStep->pTrig = pTrigger;
1142: pTrigger->pSchema = pTab->pSchema;
1143: pTrigger->pTabSchema = pTab->pSchema;
1144: pFKey->apTrigger[iAction] = pTrigger;
1145: pTrigger->op = (pChanges ? TK_UPDATE : TK_DELETE);
1146: }
1147:
1148: return pTrigger;
1149: }
1150:
1151: /*
1152: ** This function is called when deleting or updating a row to implement
1153: ** any required CASCADE, SET NULL or SET DEFAULT actions.
1154: */
1155: void sqlite3FkActions(
1156: Parse *pParse, /* Parse context */
1157: Table *pTab, /* Table being updated or deleted from */
1158: ExprList *pChanges, /* Change-list for UPDATE, NULL for DELETE */
1159: int regOld /* Address of array containing old row */
1160: ){
1161: /* If foreign-key support is enabled, iterate through all FKs that
1162: ** refer to table pTab. If there is an action associated with the FK
1163: ** for this operation (either update or delete), invoke the associated
1164: ** trigger sub-program. */
1165: if( pParse->db->flags&SQLITE_ForeignKeys ){
1166: FKey *pFKey; /* Iterator variable */
1167: for(pFKey = sqlite3FkReferences(pTab); pFKey; pFKey=pFKey->pNextTo){
1168: Trigger *pAction = fkActionTrigger(pParse, pTab, pFKey, pChanges);
1169: if( pAction ){
1170: sqlite3CodeRowTriggerDirect(pParse, pAction, pTab, regOld, OE_Abort, 0);
1171: }
1172: }
1173: }
1174: }
1175:
1176: #endif /* ifndef SQLITE_OMIT_TRIGGER */
1177:
1178: /*
1179: ** Free all memory associated with foreign key definitions attached to
1180: ** table pTab. Remove the deleted foreign keys from the Schema.fkeyHash
1181: ** hash table.
1182: */
1183: void sqlite3FkDelete(sqlite3 *db, Table *pTab){
1184: FKey *pFKey; /* Iterator variable */
1185: FKey *pNext; /* Copy of pFKey->pNextFrom */
1186:
1187: assert( db==0 || sqlite3SchemaMutexHeld(db, 0, pTab->pSchema) );
1188: for(pFKey=pTab->pFKey; pFKey; pFKey=pNext){
1189:
1190: /* Remove the FK from the fkeyHash hash table. */
1191: if( !db || db->pnBytesFreed==0 ){
1192: if( pFKey->pPrevTo ){
1193: pFKey->pPrevTo->pNextTo = pFKey->pNextTo;
1194: }else{
1195: void *p = (void *)pFKey->pNextTo;
1196: const char *z = (p ? pFKey->pNextTo->zTo : pFKey->zTo);
1197: sqlite3HashInsert(&pTab->pSchema->fkeyHash, z, sqlite3Strlen30(z), p);
1198: }
1199: if( pFKey->pNextTo ){
1200: pFKey->pNextTo->pPrevTo = pFKey->pPrevTo;
1201: }
1202: }
1203:
1204: /* EV: R-30323-21917 Each foreign key constraint in SQLite is
1205: ** classified as either immediate or deferred.
1206: */
1207: assert( pFKey->isDeferred==0 || pFKey->isDeferred==1 );
1208:
1209: /* Delete any triggers created to implement actions for this FK. */
1210: #ifndef SQLITE_OMIT_TRIGGER
1211: fkTriggerDelete(db, pFKey->apTrigger[0]);
1212: fkTriggerDelete(db, pFKey->apTrigger[1]);
1213: #endif
1214:
1215: pNext = pFKey->pNextFrom;
1216: sqlite3DbFree(db, pFKey);
1217: }
1218: }
1219: #endif /* ifndef SQLITE_OMIT_FOREIGN_KEY */
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