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,
25** SQLITE_CONSTRAINT_FOREIGNKEY is returned and the current
26** statement transaction rolled back. If a
27** deferred foreign key constraint is violated, no action is taken
28** immediately. However if the application attempts to commit the
29** transaction before fixing the constraint violation, the attempt fails.
30**
31** Deferred constraints are implemented using a simple counter associated
32** with the database handle. The counter is set to zero each time a
33** database transaction is opened. Each time a statement is executed
34** that causes a foreign key violation, the counter is incremented. Each
35** time a statement is executed that removes an existing violation from
36** the database, the counter is decremented. When the transaction is
37** committed, the commit fails if the current value of the counter is
38** greater than zero. This scheme has two big drawbacks:
39**
40** * When a commit fails due to a deferred foreign key constraint,
41** there is no way to tell which foreign constraint is not satisfied,
42** or which row it is not satisfied for.
43**
44** * If the database contains foreign key violations when the
45** transaction is opened, this may cause the mechanism to malfunction.
46**
47** Despite these problems, this approach is adopted as it seems simpler
48** than the alternatives.
49**
50** INSERT operations:
51**
52** I.1) For each FK for which the table is the child table, search
53** the parent table for a match. If none is found increment the
54** constraint counter.
55**
56** I.2) For each FK for which the table is the parent table,
57** search the child table for rows that correspond to the new
58** row in the parent table. Decrement the counter for each row
59** found (as the constraint is now satisfied).
60**
61** DELETE operations:
62**
63** D.1) For each FK for which the table is the child table,
64** search the parent table for a row that corresponds to the
65** deleted row in the child table. If such a row is not found,
66** decrement the counter.
67**
68** D.2) For each FK for which the table is the parent table, search
69** the child table for rows that correspond to the deleted row
70** in the parent table. For each found increment the counter.
71**
72** UPDATE operations:
73**
74** An UPDATE command requires that all 4 steps above are taken, but only
75** for FK constraints for which the affected columns are actually
76** modified (values must be compared at runtime).
77**
78** Note that I.1 and D.1 are very similar operations, as are I.2 and D.2.
79** This simplifies the implementation a bit.
80**
81** For the purposes of immediate FK constraints, the OR REPLACE conflict
82** resolution is considered to delete rows before the new row is inserted.
83** If a delete caused by OR REPLACE violates an FK constraint, an exception
84** is thrown, even if the FK constraint would be satisfied after the new
85** row is inserted.
86**
87** Immediate constraints are usually handled similarly. The only difference
88** is that the counter used is stored as part of each individual statement
89** object (struct Vdbe). If, after the statement has run, its immediate
90** constraint counter is greater than zero,
91** it returns SQLITE_CONSTRAINT_FOREIGNKEY
92** and the statement transaction is rolled back. An exception is an INSERT
93** statement that inserts a single row only (no triggers). In this case,
94** instead of using a counter, an exception is thrown immediately if the
95** INSERT violates a foreign key constraint. This is necessary as such
96** an INSERT does not open a statement transaction.
97**
98** TODO: How should dropping a table be handled? How should renaming a
99** table be handled?
100**
101**
102** Query API Notes
103** ---------------
104**
105** Before coding an UPDATE or DELETE row operation, the code-generator
106** for those two operations needs to know whether or not the operation
107** requires any FK processing and, if so, which columns of the original
108** row are required by the FK processing VDBE code (i.e. if FKs were
109** implemented using triggers, which of the old.* columns would be
110** accessed). No information is required by the code-generator before
111** coding an INSERT operation. The functions used by the UPDATE/DELETE
112** generation code to query for this information are:
113**
114** sqlite3FkRequired() - Test to see if FK processing is required.
115** sqlite3FkOldmask() - Query for the set of required old.* columns.
116**
117**
118** Externally accessible module functions
119** --------------------------------------
120**
121** sqlite3FkCheck() - Check for foreign key violations.
122** sqlite3FkActions() - Code triggers for ON UPDATE/ON DELETE actions.
123** sqlite3FkDelete() - Delete an FKey structure.
124*/
125
126/*
127** VDBE Calling Convention
128** -----------------------
129**
130** Example:
131**
132** For the following INSERT statement:
133**
134** CREATE TABLE t1(a, b INTEGER PRIMARY KEY, c);
135** INSERT INTO t1 VALUES(1, 2, 3.1);
136**
137** Register (x): 2 (type integer)
138** Register (x+1): 1 (type integer)
139** Register (x+2): NULL (type NULL)
140** Register (x+3): 3.1 (type real)
141*/
142
143/*
144** A foreign key constraint requires that the key columns in the parent
145** table are collectively subject to a UNIQUE or PRIMARY KEY constraint.
146** Given that pParent is the parent table for foreign key constraint pFKey,
147** search the schema for a unique index on the parent key columns.
148**
149** If successful, zero is returned. If the parent key is an INTEGER PRIMARY
150** KEY column, then output variable *ppIdx is set to NULL. Otherwise, *ppIdx
151** is set to point to the unique index.
152**
153** If the parent key consists of a single column (the foreign key constraint
154** is not a composite foreign key), output variable *paiCol is set to NULL.
155** Otherwise, it is set to point to an allocated array of size N, where
156** N is the number of columns in the parent key. The first element of the
157** array is the index of the child table column that is mapped by the FK
158** constraint to the parent table column stored in the left-most column
159** of index *ppIdx. The second element of the array is the index of the
160** child table column that corresponds to the second left-most column of
161** *ppIdx, and so on.
162**
163** If the required index cannot be found, either because:
164**
165** 1) The named parent key columns do not exist, or
166**
167** 2) The named parent key columns do exist, but are not subject to a
168** UNIQUE or PRIMARY KEY constraint, or
169**
170** 3) No parent key columns were provided explicitly as part of the
171** foreign key definition, and the parent table does not have a
172** PRIMARY KEY, or
173**
174** 4) No parent key columns were provided explicitly as part of the
175** foreign key definition, and the PRIMARY KEY of the parent table
176** consists of a different number of columns to the child key in
177** the child table.
178**
179** then non-zero is returned, and a "foreign key mismatch" error loaded
180** into pParse. If an OOM error occurs, non-zero is returned and the
181** pParse->db->mallocFailed flag is set.
182*/
183int sqlite3FkLocateIndex(
184 Parse *pParse, /* Parse context to store any error in */
185 Table *pParent, /* Parent table of FK constraint pFKey */
186 FKey *pFKey, /* Foreign key to find index for */
187 Index **ppIdx, /* OUT: Unique index on parent table */
188 int **paiCol /* OUT: Map of index columns in pFKey */
189){
190 Index *pIdx = 0; /* Value to return via *ppIdx */
191 int *aiCol = 0; /* Value to return via *paiCol */
192 int nCol = pFKey->nCol; /* Number of columns in parent key */
193 char *zKey = pFKey->aCol[0].zCol; /* Name of left-most parent key column */
194
195 /* The caller is responsible for zeroing output parameters. */
196 assert( ppIdx && *ppIdx==0 );
197 assert( !paiCol || *paiCol==0 );
198 assert( pParse );
199
200 /* If this is a non-composite (single column) foreign key, check if it
201 ** maps to the INTEGER PRIMARY KEY of table pParent. If so, leave *ppIdx
202 ** and *paiCol set to zero and return early.
203 **
204 ** Otherwise, for a composite foreign key (more than one column), allocate
205 ** space for the aiCol array (returned via output parameter *paiCol).
206 ** Non-composite foreign keys do not require the aiCol array.
207 */
208 if( nCol==1 ){
209 /* The FK maps to the IPK if any of the following are true:
210 **
211 ** 1) There is an INTEGER PRIMARY KEY column and the FK is implicitly
212 ** mapped to the primary key of table pParent, or
213 ** 2) The FK is explicitly mapped to a column declared as INTEGER
214 ** PRIMARY KEY.
215 */
216 if( pParent->iPKey>=0 ){
217 if( !zKey ) return 0;
218 if( !sqlite3StrICmp(pParent->aCol[pParent->iPKey].zCnName, zKey) ){
219 return 0;
220 }
221 }
222 }else if( paiCol ){
223 assert( nCol>1 );
224 aiCol = (int *)sqlite3DbMallocRawNN(pParse->db, nCol*sizeof(int));
225 if( !aiCol ) return 1;
226 *paiCol = aiCol;
227 }
228
229 for(pIdx=pParent->pIndex; pIdx; pIdx=pIdx->pNext){
230 if( pIdx->nKeyCol==nCol && IsUniqueIndex(pIdx) && pIdx->pPartIdxWhere==0 ){
231 /* pIdx is a UNIQUE index (or a PRIMARY KEY) and has the right number
232 ** of columns. If each indexed column corresponds to a foreign key
233 ** column of pFKey, then this index is a winner. */
234
235 if( zKey==0 ){
236 /* If zKey is NULL, then this foreign key is implicitly mapped to
237 ** the PRIMARY KEY of table pParent. The PRIMARY KEY index may be
238 ** identified by the test. */
239 if( IsPrimaryKeyIndex(pIdx) ){
240 if( aiCol ){
241 int i;
242 for(i=0; i<nCol; i++) aiCol[i] = pFKey->aCol[i].iFrom;
243 }
244 break;
245 }
246 }else{
247 /* If zKey is non-NULL, then this foreign key was declared to
248 ** map to an explicit list of columns in table pParent. Check if this
249 ** index matches those columns. Also, check that the index uses
250 ** the default collation sequences for each column. */
251 int i, j;
252 for(i=0; i<nCol; i++){
253 i16 iCol = pIdx->aiColumn[i]; /* Index of column in parent tbl */
254 const char *zDfltColl; /* Def. collation for column */
255 char *zIdxCol; /* Name of indexed column */
256
257 if( iCol<0 ) break; /* No foreign keys against expression indexes */
258
259 /* If the index uses a collation sequence that is different from
260 ** the default collation sequence for the column, this index is
261 ** unusable. Bail out early in this case. */
262 zDfltColl = sqlite3ColumnColl(&pParent->aCol[iCol]);
263 if( !zDfltColl ) zDfltColl = sqlite3StrBINARY;
264 if( sqlite3StrICmp(pIdx->azColl[i], zDfltColl) ) break;
265
266 zIdxCol = pParent->aCol[iCol].zCnName;
267 for(j=0; j<nCol; j++){
268 if( sqlite3StrICmp(pFKey->aCol[j].zCol, zIdxCol)==0 ){
269 if( aiCol ) aiCol[i] = pFKey->aCol[j].iFrom;
270 break;
271 }
272 }
273 if( j==nCol ) break;
274 }
275 if( i==nCol ) break; /* pIdx is usable */
276 }
277 }
278 }
279
280 if( !pIdx ){
281 if( !pParse->disableTriggers ){
282 sqlite3ErrorMsg(pParse,
283 "foreign key mismatch - \"%w\" referencing \"%w\"",
284 pFKey->pFrom->zName, pFKey->zTo);
285 }
286 sqlite3DbFree(pParse->db, aiCol);
287 return 1;
288 }
289
290 *ppIdx = pIdx;
291 return 0;
292}
293
294/*
295** This function is called when a row is inserted into or deleted from the
296** child table of foreign key constraint pFKey. If an SQL UPDATE is executed
297** on the child table of pFKey, this function is invoked twice for each row
298** affected - once to "delete" the old row, and then again to "insert" the
299** new row.
300**
301** Each time it is called, this function generates VDBE code to locate the
302** row in the parent table that corresponds to the row being inserted into
303** or deleted from the child table. If the parent row can be found, no
304** special action is taken. Otherwise, if the parent row can *not* be
305** found in the parent table:
306**
307** Operation | FK type | Action taken
308** --------------------------------------------------------------------------
309** INSERT immediate Increment the "immediate constraint counter".
310**
311** DELETE immediate Decrement the "immediate constraint counter".
312**
313** INSERT deferred Increment the "deferred constraint counter".
314**
315** DELETE deferred Decrement the "deferred constraint counter".
316**
317** These operations are identified in the comment at the top of this file
318** (fkey.c) as "I.1" and "D.1".
319*/
320static void fkLookupParent(
321 Parse *pParse, /* Parse context */
322 int iDb, /* Index of database housing pTab */
323 Table *pTab, /* Parent table of FK pFKey */
324 Index *pIdx, /* Unique index on parent key columns in pTab */
325 FKey *pFKey, /* Foreign key constraint */
326 int *aiCol, /* Map from parent key columns to child table columns */
327 int regData, /* Address of array containing child table row */
328 int nIncr, /* Increment constraint counter by this */
329 int isIgnore /* If true, pretend pTab contains all NULL values */
330){
331 int i; /* Iterator variable */
332 Vdbe *v = sqlite3GetVdbe(pParse); /* Vdbe to add code to */
333 int iCur = pParse->nTab - 1; /* Cursor number to use */
334 int iOk = sqlite3VdbeMakeLabel(pParse); /* jump here if parent key found */
335
336 sqlite3VdbeVerifyAbortable(v,
337 (!pFKey->isDeferred
338 && !(pParse->db->flags & SQLITE_DeferFKs)
339 && !pParse->pToplevel
340 && !pParse->isMultiWrite) ? OE_Abort : OE_Ignore);
341
342 /* If nIncr is less than zero, then check at runtime if there are any
343 ** outstanding constraints to resolve. If there are not, there is no need
344 ** to check if deleting this row resolves any outstanding violations.
345 **
346 ** Check if any of the key columns in the child table row are NULL. If
347 ** any are, then the constraint is considered satisfied. No need to
348 ** search for a matching row in the parent table. */
349 if( nIncr<0 ){
350 sqlite3VdbeAddOp2(v, OP_FkIfZero, pFKey->isDeferred, iOk);
351 VdbeCoverage(v);
352 }
353 for(i=0; i<pFKey->nCol; i++){
354 int iReg = sqlite3TableColumnToStorage(pFKey->pFrom,aiCol[i]) + regData + 1;
355 sqlite3VdbeAddOp2(v, OP_IsNull, iReg, iOk); VdbeCoverage(v);
356 }
357
358 if( isIgnore==0 ){
359 if( pIdx==0 ){
360 /* If pIdx is NULL, then the parent key is the INTEGER PRIMARY KEY
361 ** column of the parent table (table pTab). */
362 int iMustBeInt; /* Address of MustBeInt instruction */
363 int regTemp = sqlite3GetTempReg(pParse);
364
365 /* Invoke MustBeInt to coerce the child key value to an integer (i.e.
366 ** apply the affinity of the parent key). If this fails, then there
367 ** is no matching parent key. Before using MustBeInt, make a copy of
368 ** the value. Otherwise, the value inserted into the child key column
369 ** will have INTEGER affinity applied to it, which may not be correct. */
370 sqlite3VdbeAddOp2(v, OP_SCopy,
371 sqlite3TableColumnToStorage(pFKey->pFrom,aiCol[0])+1+regData, regTemp);
372 iMustBeInt = sqlite3VdbeAddOp2(v, OP_MustBeInt, regTemp, 0);
373 VdbeCoverage(v);
374
375 /* If the parent table is the same as the child table, and we are about
376 ** to increment the constraint-counter (i.e. this is an INSERT operation),
377 ** then check if the row being inserted matches itself. If so, do not
378 ** increment the constraint-counter. */
379 if( pTab==pFKey->pFrom && nIncr==1 ){
380 sqlite3VdbeAddOp3(v, OP_Eq, regData, iOk, regTemp); VdbeCoverage(v);
381 sqlite3VdbeChangeP5(v, SQLITE_NOTNULL);
382 }
383
384 sqlite3OpenTable(pParse, iCur, iDb, pTab, OP_OpenRead);
385 sqlite3VdbeAddOp3(v, OP_NotExists, iCur, 0, regTemp); VdbeCoverage(v);
386 sqlite3VdbeGoto(v, iOk);
387 sqlite3VdbeJumpHere(v, sqlite3VdbeCurrentAddr(v)-2);
388 sqlite3VdbeJumpHere(v, iMustBeInt);
389 sqlite3ReleaseTempReg(pParse, regTemp);
390 }else{
391 int nCol = pFKey->nCol;
392 int regTemp = sqlite3GetTempRange(pParse, nCol);
393
394 sqlite3VdbeAddOp3(v, OP_OpenRead, iCur, pIdx->tnum, iDb);
395 sqlite3VdbeSetP4KeyInfo(pParse, pIdx);
396 for(i=0; i<nCol; i++){
397 sqlite3VdbeAddOp2(v, OP_Copy,
398 sqlite3TableColumnToStorage(pFKey->pFrom, aiCol[i])+1+regData,
399 regTemp+i);
400 }
401
402 /* If the parent table is the same as the child table, and we are about
403 ** to increment the constraint-counter (i.e. this is an INSERT operation),
404 ** then check if the row being inserted matches itself. If so, do not
405 ** increment the constraint-counter.
406 **
407 ** If any of the parent-key values are NULL, then the row cannot match
408 ** itself. So set JUMPIFNULL to make sure we do the OP_Found if any
409 ** of the parent-key values are NULL (at this point it is known that
410 ** none of the child key values are).
411 */
412 if( pTab==pFKey->pFrom && nIncr==1 ){
413 int iJump = sqlite3VdbeCurrentAddr(v) + nCol + 1;
414 for(i=0; i<nCol; i++){
415 int iChild = sqlite3TableColumnToStorage(pFKey->pFrom,aiCol[i])
416 +1+regData;
417 int iParent = 1+regData;
418 iParent += sqlite3TableColumnToStorage(pIdx->pTable,
419 pIdx->aiColumn[i]);
420 assert( pIdx->aiColumn[i]>=0 );
421 assert( aiCol[i]!=pTab->iPKey );
422 if( pIdx->aiColumn[i]==pTab->iPKey ){
423 /* The parent key is a composite key that includes the IPK column */
424 iParent = regData;
425 }
426 sqlite3VdbeAddOp3(v, OP_Ne, iChild, iJump, iParent); VdbeCoverage(v);
427 sqlite3VdbeChangeP5(v, SQLITE_JUMPIFNULL);
428 }
429 sqlite3VdbeGoto(v, iOk);
430 }
431
432 sqlite3VdbeAddOp4(v, OP_Affinity, regTemp, nCol, 0,
433 sqlite3IndexAffinityStr(pParse->db,pIdx), nCol);
434 sqlite3VdbeAddOp4Int(v, OP_Found, iCur, iOk, regTemp, nCol);
435 VdbeCoverage(v);
436 sqlite3ReleaseTempRange(pParse, regTemp, nCol);
437 }
438 }
439
440 if( !pFKey->isDeferred && !(pParse->db->flags & SQLITE_DeferFKs)
441 && !pParse->pToplevel
442 && !pParse->isMultiWrite
443 ){
444 /* Special case: If this is an INSERT statement that will insert exactly
445 ** one row into the table, raise a constraint immediately instead of
446 ** incrementing a counter. This is necessary as the VM code is being
447 ** generated for will not open a statement transaction. */
448 assert( nIncr==1 );
449 sqlite3HaltConstraint(pParse, SQLITE_CONSTRAINT_FOREIGNKEY,
450 OE_Abort, 0, P4_STATIC, P5_ConstraintFK);
451 }else{
452 if( nIncr>0 && pFKey->isDeferred==0 ){
453 sqlite3MayAbort(pParse);
454 }
455 sqlite3VdbeAddOp2(v, OP_FkCounter, pFKey->isDeferred, nIncr);
456 }
457
458 sqlite3VdbeResolveLabel(v, iOk);
459 sqlite3VdbeAddOp1(v, OP_Close, iCur);
460}
461
462
463/*
464** Return an Expr object that refers to a memory register corresponding
465** to column iCol of table pTab.
466**
467** regBase is the first of an array of register that contains the data
468** for pTab. regBase itself holds the rowid. regBase+1 holds the first
469** column. regBase+2 holds the second column, and so forth.
470*/
471static Expr *exprTableRegister(
472 Parse *pParse, /* Parsing and code generating context */
473 Table *pTab, /* The table whose content is at r[regBase]... */
474 int regBase, /* Contents of table pTab */
475 i16 iCol /* Which column of pTab is desired */
476){
477 Expr *pExpr;
478 Column *pCol;
479 const char *zColl;
480 sqlite3 *db = pParse->db;
481
482 pExpr = sqlite3Expr(db, TK_REGISTER, 0);
483 if( pExpr ){
484 if( iCol>=0 && iCol!=pTab->iPKey ){
485 pCol = &pTab->aCol[iCol];
486 pExpr->iTable = regBase + sqlite3TableColumnToStorage(pTab,iCol) + 1;
487 pExpr->affExpr = pCol->affinity;
488 zColl = sqlite3ColumnColl(pCol);
489 if( zColl==0 ) zColl = db->pDfltColl->zName;
490 pExpr = sqlite3ExprAddCollateString(pParse, pExpr, zColl);
491 }else{
492 pExpr->iTable = regBase;
493 pExpr->affExpr = SQLITE_AFF_INTEGER;
494 }
495 }
496 return pExpr;
497}
498
499/*
500** Return an Expr object that refers to column iCol of table pTab which
501** has cursor iCur.
502*/
503static Expr *exprTableColumn(
504 sqlite3 *db, /* The database connection */
505 Table *pTab, /* The table whose column is desired */
506 int iCursor, /* The open cursor on the table */
507 i16 iCol /* The column that is wanted */
508){
509 Expr *pExpr = sqlite3Expr(db, TK_COLUMN, 0);
510 if( pExpr ){
511 assert( ExprUseYTab(pExpr) );
512 pExpr->y.pTab = pTab;
513 pExpr->iTable = iCursor;
514 pExpr->iColumn = iCol;
515 }
516 return pExpr;
517}
518
519/*
520** This function is called to generate code executed when a row is deleted
521** from the parent table of foreign key constraint pFKey and, if pFKey is
522** deferred, when a row is inserted into the same table. When generating
523** code for an SQL UPDATE operation, this function may be called twice -
524** once to "delete" the old row and once to "insert" the new row.
525**
526** Parameter nIncr is passed -1 when inserting a row (as this may decrease
527** the number of FK violations in the db) or +1 when deleting one (as this
528** may increase the number of FK constraint problems).
529**
530** The code generated by this function scans through the rows in the child
531** table that correspond to the parent table row being deleted or inserted.
532** For each child row found, one of the following actions is taken:
533**
534** Operation | FK type | Action taken
535** --------------------------------------------------------------------------
536** DELETE immediate Increment the "immediate constraint counter".
537**
538** INSERT immediate Decrement the "immediate constraint counter".
539**
540** DELETE deferred Increment the "deferred constraint counter".
541**
542** INSERT deferred Decrement the "deferred constraint counter".
543**
544** These operations are identified in the comment at the top of this file
545** (fkey.c) as "I.2" and "D.2".
546*/
547static void fkScanChildren(
548 Parse *pParse, /* Parse context */
549 SrcList *pSrc, /* The child table to be scanned */
550 Table *pTab, /* The parent table */
551 Index *pIdx, /* Index on parent covering the foreign key */
552 FKey *pFKey, /* The foreign key linking pSrc to pTab */
553 int *aiCol, /* Map from pIdx cols to child table cols */
554 int regData, /* Parent row data starts here */
555 int nIncr /* Amount to increment deferred counter by */
556){
557 sqlite3 *db = pParse->db; /* Database handle */
558 int i; /* Iterator variable */
559 Expr *pWhere = 0; /* WHERE clause to scan with */
560 NameContext sNameContext; /* Context used to resolve WHERE clause */
561 WhereInfo *pWInfo; /* Context used by sqlite3WhereXXX() */
562 int iFkIfZero = 0; /* Address of OP_FkIfZero */
563 Vdbe *v = sqlite3GetVdbe(pParse);
564
565 assert( pIdx==0 || pIdx->pTable==pTab );
566 assert( pIdx==0 || pIdx->nKeyCol==pFKey->nCol );
567 assert( pIdx!=0 || pFKey->nCol==1 );
568 assert( pIdx!=0 || HasRowid(pTab) );
569
570 if( nIncr<0 ){
571 iFkIfZero = sqlite3VdbeAddOp2(v, OP_FkIfZero, pFKey->isDeferred, 0);
572 VdbeCoverage(v);
573 }
574
575 /* Create an Expr object representing an SQL expression like:
576 **
577 ** <parent-key1> = <child-key1> AND <parent-key2> = <child-key2> ...
578 **
579 ** The collation sequence used for the comparison should be that of
580 ** the parent key columns. The affinity of the parent key column should
581 ** be applied to each child key value before the comparison takes place.
582 */
583 for(i=0; i<pFKey->nCol; i++){
584 Expr *pLeft; /* Value from parent table row */
585 Expr *pRight; /* Column ref to child table */
586 Expr *pEq; /* Expression (pLeft = pRight) */
587 i16 iCol; /* Index of column in child table */
588 const char *zCol; /* Name of column in child table */
589
590 iCol = pIdx ? pIdx->aiColumn[i] : -1;
591 pLeft = exprTableRegister(pParse, pTab, regData, iCol);
592 iCol = aiCol ? aiCol[i] : pFKey->aCol[0].iFrom;
593 assert( iCol>=0 );
594 zCol = pFKey->pFrom->aCol[iCol].zCnName;
595 pRight = sqlite3Expr(db, TK_ID, zCol);
596 pEq = sqlite3PExpr(pParse, TK_EQ, pLeft, pRight);
597 pWhere = sqlite3ExprAnd(pParse, pWhere, pEq);
598 }
599
600 /* If the child table is the same as the parent table, then add terms
601 ** to the WHERE clause that prevent this entry from being scanned.
602 ** The added WHERE clause terms are like this:
603 **
604 ** $current_rowid!=rowid
605 ** NOT( $current_a==a AND $current_b==b AND ... )
606 **
607 ** The first form is used for rowid tables. The second form is used
608 ** for WITHOUT ROWID tables. In the second form, the *parent* key is
609 ** (a,b,...). Either the parent or primary key could be used to
610 ** uniquely identify the current row, but the parent key is more convenient
611 ** as the required values have already been loaded into registers
612 ** by the caller.
613 */
614 if( pTab==pFKey->pFrom && nIncr>0 ){
615 Expr *pNe; /* Expression (pLeft != pRight) */
616 Expr *pLeft; /* Value from parent table row */
617 Expr *pRight; /* Column ref to child table */
618 if( HasRowid(pTab) ){
619 pLeft = exprTableRegister(pParse, pTab, regData, -1);
620 pRight = exprTableColumn(db, pTab, pSrc->a[0].iCursor, -1);
621 pNe = sqlite3PExpr(pParse, TK_NE, pLeft, pRight);
622 }else{
623 Expr *pEq, *pAll = 0;
624 assert( pIdx!=0 );
625 for(i=0; i<pIdx->nKeyCol; i++){
626 i16 iCol = pIdx->aiColumn[i];
627 assert( iCol>=0 );
628 pLeft = exprTableRegister(pParse, pTab, regData, iCol);
629 pRight = sqlite3Expr(db, TK_ID, pTab->aCol[iCol].zCnName);
630 pEq = sqlite3PExpr(pParse, TK_IS, pLeft, pRight);
631 pAll = sqlite3ExprAnd(pParse, pAll, pEq);
632 }
633 pNe = sqlite3PExpr(pParse, TK_NOT, pAll, 0);
634 }
635 pWhere = sqlite3ExprAnd(pParse, pWhere, pNe);
636 }
637
638 /* Resolve the references in the WHERE clause. */
639 memset(&sNameContext, 0, sizeof(NameContext));
640 sNameContext.pSrcList = pSrc;
641 sNameContext.pParse = pParse;
642 sqlite3ResolveExprNames(&sNameContext, pWhere);
643
644 /* Create VDBE to loop through the entries in pSrc that match the WHERE
645 ** clause. For each row found, increment either the deferred or immediate
646 ** foreign key constraint counter. */
647 if( pParse->nErr==0 ){
648 pWInfo = sqlite3WhereBegin(pParse, pSrc, pWhere, 0, 0, 0, 0, 0);
649 sqlite3VdbeAddOp2(v, OP_FkCounter, pFKey->isDeferred, nIncr);
650 if( pWInfo ){
651 sqlite3WhereEnd(pWInfo);
652 }
653 }
654
655 /* Clean up the WHERE clause constructed above. */
656 sqlite3ExprDelete(db, pWhere);
657 if( iFkIfZero ){
658 sqlite3VdbeJumpHereOrPopInst(v, iFkIfZero);
659 }
660}
661
662/*
663** This function returns a linked list of FKey objects (connected by
664** FKey.pNextTo) holding all children of table pTab. For example,
665** given the following schema:
666**
667** CREATE TABLE t1(a PRIMARY KEY);
668** CREATE TABLE t2(b REFERENCES t1(a);
669**
670** Calling this function with table "t1" as an argument returns a pointer
671** to the FKey structure representing the foreign key constraint on table
672** "t2". Calling this function with "t2" as the argument would return a
673** NULL pointer (as there are no FK constraints for which t2 is the parent
674** table).
675*/
676FKey *sqlite3FkReferences(Table *pTab){
677 return (FKey *)sqlite3HashFind(&pTab->pSchema->fkeyHash, pTab->zName);
678}
679
680/*
681** The second argument is a Trigger structure allocated by the
682** fkActionTrigger() routine. This function deletes the Trigger structure
683** and all of its sub-components.
684**
685** The Trigger structure or any of its sub-components may be allocated from
686** the lookaside buffer belonging to database handle dbMem.
687*/
688static void fkTriggerDelete(sqlite3 *dbMem, Trigger *p){
689 if( p ){
690 TriggerStep *pStep = p->step_list;
691 sqlite3ExprDelete(dbMem, pStep->pWhere);
692 sqlite3ExprListDelete(dbMem, pStep->pExprList);
693 sqlite3SelectDelete(dbMem, pStep->pSelect);
694 sqlite3ExprDelete(dbMem, p->pWhen);
695 sqlite3DbFree(dbMem, p);
696 }
697}
698
699/*
700** Clear the apTrigger[] cache of CASCADE triggers for all foreign keys
701** in a particular database. This needs to happen when the schema
702** changes.
703*/
704void sqlite3FkClearTriggerCache(sqlite3 *db, int iDb){
705 HashElem *k;
706 Hash *pHash = &db->aDb[iDb].pSchema->tblHash;
707 for(k=sqliteHashFirst(pHash); k; k=sqliteHashNext(k)){
708 Table *pTab = sqliteHashData(k);
709 FKey *pFKey;
710 if( !IsOrdinaryTable(pTab) ) continue;
711 for(pFKey=pTab->u.tab.pFKey; pFKey; pFKey=pFKey->pNextFrom){
712 fkTriggerDelete(db, pFKey->apTrigger[0]); pFKey->apTrigger[0] = 0;
713 fkTriggerDelete(db, pFKey->apTrigger[1]); pFKey->apTrigger[1] = 0;
714 }
715 }
716}
717
718/*
719** This function is called to generate code that runs when table pTab is
720** being dropped from the database. The SrcList passed as the second argument
721** to this function contains a single entry guaranteed to resolve to
722** table pTab.
723**
724** Normally, no code is required. However, if either
725**
726** (a) The table is the parent table of a FK constraint, or
727** (b) The table is the child table of a deferred FK constraint and it is
728** determined at runtime that there are outstanding deferred FK
729** constraint violations in the database,
730**
731** then the equivalent of "DELETE FROM <tbl>" is executed before dropping
732** the table from the database. Triggers are disabled while running this
733** DELETE, but foreign key actions are not.
734*/
735void sqlite3FkDropTable(Parse *pParse, SrcList *pName, Table *pTab){
736 sqlite3 *db = pParse->db;
737 if( (db->flags&SQLITE_ForeignKeys) && IsOrdinaryTable(pTab) ){
738 int iSkip = 0;
739 Vdbe *v = sqlite3GetVdbe(pParse);
740
741 assert( v ); /* VDBE has already been allocated */
742 assert( IsOrdinaryTable(pTab) );
743 if( sqlite3FkReferences(pTab)==0 ){
744 /* Search for a deferred foreign key constraint for which this table
745 ** is the child table. If one cannot be found, return without
746 ** generating any VDBE code. If one can be found, then jump over
747 ** the entire DELETE if there are no outstanding deferred constraints
748 ** when this statement is run. */
749 FKey *p;
750 for(p=pTab->u.tab.pFKey; p; p=p->pNextFrom){
751 if( p->isDeferred || (db->flags & SQLITE_DeferFKs) ) break;
752 }
753 if( !p ) return;
754 iSkip = sqlite3VdbeMakeLabel(pParse);
755 sqlite3VdbeAddOp2(v, OP_FkIfZero, 1, iSkip); VdbeCoverage(v);
756 }
757
758 pParse->disableTriggers = 1;
759 sqlite3DeleteFrom(pParse, sqlite3SrcListDup(db, pName, 0), 0, 0, 0);
760 pParse->disableTriggers = 0;
761
762 /* If the DELETE has generated immediate foreign key constraint
763 ** violations, halt the VDBE and return an error at this point, before
764 ** any modifications to the schema are made. This is because statement
765 ** transactions are not able to rollback schema changes.
766 **
767 ** If the SQLITE_DeferFKs flag is set, then this is not required, as
768 ** the statement transaction will not be rolled back even if FK
769 ** constraints are violated.
770 */
771 if( (db->flags & SQLITE_DeferFKs)==0 ){
772 sqlite3VdbeVerifyAbortable(v, OE_Abort);
773 sqlite3VdbeAddOp2(v, OP_FkIfZero, 0, sqlite3VdbeCurrentAddr(v)+2);
774 VdbeCoverage(v);
775 sqlite3HaltConstraint(pParse, SQLITE_CONSTRAINT_FOREIGNKEY,
776 OE_Abort, 0, P4_STATIC, P5_ConstraintFK);
777 }
778
779 if( iSkip ){
780 sqlite3VdbeResolveLabel(v, iSkip);
781 }
782 }
783}
784
785
786/*
787** The second argument points to an FKey object representing a foreign key
788** for which pTab is the child table. An UPDATE statement against pTab
789** is currently being processed. For each column of the table that is
790** actually updated, the corresponding element in the aChange[] array
791** is zero or greater (if a column is unmodified the corresponding element
792** is set to -1). If the rowid column is modified by the UPDATE statement
793** the bChngRowid argument is non-zero.
794**
795** This function returns true if any of the columns that are part of the
796** child key for FK constraint *p are modified.
797*/
798static int fkChildIsModified(
799 Table *pTab, /* Table being updated */
800 FKey *p, /* Foreign key for which pTab is the child */
801 int *aChange, /* Array indicating modified columns */
802 int bChngRowid /* True if rowid is modified by this update */
803){
804 int i;
805 for(i=0; i<p->nCol; i++){
806 int iChildKey = p->aCol[i].iFrom;
807 if( aChange[iChildKey]>=0 ) return 1;
808 if( iChildKey==pTab->iPKey && bChngRowid ) return 1;
809 }
810 return 0;
811}
812
813/*
814** The second argument points to an FKey object representing a foreign key
815** for which pTab is the parent table. An UPDATE statement against pTab
816** is currently being processed. For each column of the table that is
817** actually updated, the corresponding element in the aChange[] array
818** is zero or greater (if a column is unmodified the corresponding element
819** is set to -1). If the rowid column is modified by the UPDATE statement
820** the bChngRowid argument is non-zero.
821**
822** This function returns true if any of the columns that are part of the
823** parent key for FK constraint *p are modified.
824*/
825static int fkParentIsModified(
826 Table *pTab,
827 FKey *p,
828 int *aChange,
829 int bChngRowid
830){
831 int i;
832 for(i=0; i<p->nCol; i++){
833 char *zKey = p->aCol[i].zCol;
834 int iKey;
835 for(iKey=0; iKey<pTab->nCol; iKey++){
836 if( aChange[iKey]>=0 || (iKey==pTab->iPKey && bChngRowid) ){
837 Column *pCol = &pTab->aCol[iKey];
838 if( zKey ){
839 if( 0==sqlite3StrICmp(pCol->zCnName, zKey) ) return 1;
840 }else if( pCol->colFlags & COLFLAG_PRIMKEY ){
841 return 1;
842 }
843 }
844 }
845 }
846 return 0;
847}
848
849/*
850** Return true if the parser passed as the first argument is being
851** used to code a trigger that is really a "SET NULL" action belonging
852** to trigger pFKey.
853*/
854static int isSetNullAction(Parse *pParse, FKey *pFKey){
855 Parse *pTop = sqlite3ParseToplevel(pParse);
856 if( pTop->pTriggerPrg ){
857 Trigger *p = pTop->pTriggerPrg->pTrigger;
858 if( (p==pFKey->apTrigger[0] && pFKey->aAction[0]==OE_SetNull)
859 || (p==pFKey->apTrigger[1] && pFKey->aAction[1]==OE_SetNull)
860 ){
861 return 1;
862 }
863 }
864 return 0;
865}
866
867/*
868** This function is called when inserting, deleting or updating a row of
869** table pTab to generate VDBE code to perform foreign key constraint
870** processing for the operation.
871**
872** For a DELETE operation, parameter regOld is passed the index of the
873** first register in an array of (pTab->nCol+1) registers containing the
874** rowid of the row being deleted, followed by each of the column values
875** of the row being deleted, from left to right. Parameter regNew is passed
876** zero in this case.
877**
878** For an INSERT operation, regOld is passed zero and regNew is passed the
879** first register of an array of (pTab->nCol+1) registers containing the new
880** row data.
881**
882** For an UPDATE operation, this function is called twice. Once before
883** the original record is deleted from the table using the calling convention
884** described for DELETE. Then again after the original record is deleted
885** but before the new record is inserted using the INSERT convention.
886*/
887void sqlite3FkCheck(
888 Parse *pParse, /* Parse context */
889 Table *pTab, /* Row is being deleted from this table */
890 int regOld, /* Previous row data is stored here */
891 int regNew, /* New row data is stored here */
892 int *aChange, /* Array indicating UPDATEd columns (or 0) */
893 int bChngRowid /* True if rowid is UPDATEd */
894){
895 sqlite3 *db = pParse->db; /* Database handle */
896 FKey *pFKey; /* Used to iterate through FKs */
897 int iDb; /* Index of database containing pTab */
898 const char *zDb; /* Name of database containing pTab */
899 int isIgnoreErrors = pParse->disableTriggers;
900
901 /* Exactly one of regOld and regNew should be non-zero. */
902 assert( (regOld==0)!=(regNew==0) );
903
904 /* If foreign-keys are disabled, this function is a no-op. */
905 if( (db->flags&SQLITE_ForeignKeys)==0 ) return;
906 if( !IsOrdinaryTable(pTab) ) return;
907
908 iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
909 zDb = db->aDb[iDb].zDbSName;
910
911 /* Loop through all the foreign key constraints for which pTab is the
912 ** child table (the table that the foreign key definition is part of). */
913 for(pFKey=pTab->u.tab.pFKey; pFKey; pFKey=pFKey->pNextFrom){
914 Table *pTo; /* Parent table of foreign key pFKey */
915 Index *pIdx = 0; /* Index on key columns in pTo */
916 int *aiFree = 0;
917 int *aiCol;
918 int iCol;
919 int i;
920 int bIgnore = 0;
921
922 if( aChange
923 && sqlite3_stricmp(pTab->zName, pFKey->zTo)!=0
924 && fkChildIsModified(pTab, pFKey, aChange, bChngRowid)==0
925 ){
926 continue;
927 }
928
929 /* Find the parent table of this foreign key. Also find a unique index
930 ** on the parent key columns in the parent table. If either of these
931 ** schema items cannot be located, set an error in pParse and return
932 ** early. */
933 if( pParse->disableTriggers ){
934 pTo = sqlite3FindTable(db, pFKey->zTo, zDb);
935 }else{
936 pTo = sqlite3LocateTable(pParse, 0, pFKey->zTo, zDb);
937 }
938 if( !pTo || sqlite3FkLocateIndex(pParse, pTo, pFKey, &pIdx, &aiFree) ){
939 assert( isIgnoreErrors==0 || (regOld!=0 && regNew==0) );
940 if( !isIgnoreErrors || db->mallocFailed ) return;
941 if( pTo==0 ){
942 /* If isIgnoreErrors is true, then a table is being dropped. In this
943 ** case SQLite runs a "DELETE FROM xxx" on the table being dropped
944 ** before actually dropping it in order to check FK constraints.
945 ** If the parent table of an FK constraint on the current table is
946 ** missing, behave as if it is empty. i.e. decrement the relevant
947 ** FK counter for each row of the current table with non-NULL keys.
948 */
949 Vdbe *v = sqlite3GetVdbe(pParse);
950 int iJump = sqlite3VdbeCurrentAddr(v) + pFKey->nCol + 1;
951 for(i=0; i<pFKey->nCol; i++){
952 int iFromCol, iReg;
953 iFromCol = pFKey->aCol[i].iFrom;
954 iReg = sqlite3TableColumnToStorage(pFKey->pFrom,iFromCol) + regOld+1;
955 sqlite3VdbeAddOp2(v, OP_IsNull, iReg, iJump); VdbeCoverage(v);
956 }
957 sqlite3VdbeAddOp2(v, OP_FkCounter, pFKey->isDeferred, -1);
958 }
959 continue;
960 }
961 assert( pFKey->nCol==1 || (aiFree && pIdx) );
962
963 if( aiFree ){
964 aiCol = aiFree;
965 }else{
966 iCol = pFKey->aCol[0].iFrom;
967 aiCol = &iCol;
968 }
969 for(i=0; i<pFKey->nCol; i++){
970 if( aiCol[i]==pTab->iPKey ){
971 aiCol[i] = -1;
972 }
973 assert( pIdx==0 || pIdx->aiColumn[i]>=0 );
974#ifndef SQLITE_OMIT_AUTHORIZATION
975 /* Request permission to read the parent key columns. If the
976 ** authorization callback returns SQLITE_IGNORE, behave as if any
977 ** values read from the parent table are NULL. */
978 if( db->xAuth ){
979 int rcauth;
980 char *zCol = pTo->aCol[pIdx ? pIdx->aiColumn[i] : pTo->iPKey].zCnName;
981 rcauth = sqlite3AuthReadCol(pParse, pTo->zName, zCol, iDb);
982 bIgnore = (rcauth==SQLITE_IGNORE);
983 }
984#endif
985 }
986
987 /* Take a shared-cache advisory read-lock on the parent table. Allocate
988 ** a cursor to use to search the unique index on the parent key columns
989 ** in the parent table. */
990 sqlite3TableLock(pParse, iDb, pTo->tnum, 0, pTo->zName);
991 pParse->nTab++;
992
993 if( regOld!=0 ){
994 /* A row is being removed from the child table. Search for the parent.
995 ** If the parent does not exist, removing the child row resolves an
996 ** outstanding foreign key constraint violation. */
997 fkLookupParent(pParse, iDb, pTo, pIdx, pFKey, aiCol, regOld, -1, bIgnore);
998 }
999 if( regNew!=0 && !isSetNullAction(pParse, pFKey) ){
1000 /* A row is being added to the child table. If a parent row cannot
1001 ** be found, adding the child row has violated the FK constraint.
1002 **
1003 ** If this operation is being performed as part of a trigger program
1004 ** that is actually a "SET NULL" action belonging to this very
1005 ** foreign key, then omit this scan altogether. As all child key
1006 ** values are guaranteed to be NULL, it is not possible for adding
1007 ** this row to cause an FK violation. */
1008 fkLookupParent(pParse, iDb, pTo, pIdx, pFKey, aiCol, regNew, +1, bIgnore);
1009 }
1010
1011 sqlite3DbFree(db, aiFree);
1012 }
1013
1014 /* Loop through all the foreign key constraints that refer to this table.
1015 ** (the "child" constraints) */
1016 for(pFKey = sqlite3FkReferences(pTab); pFKey; pFKey=pFKey->pNextTo){
1017 Index *pIdx = 0; /* Foreign key index for pFKey */
1018 SrcList *pSrc;
1019 int *aiCol = 0;
1020
1021 if( aChange && fkParentIsModified(pTab, pFKey, aChange, bChngRowid)==0 ){
1022 continue;
1023 }
1024
1025 if( !pFKey->isDeferred && !(db->flags & SQLITE_DeferFKs)
1026 && !pParse->pToplevel && !pParse->isMultiWrite
1027 ){
1028 assert( regOld==0 && regNew!=0 );
1029 /* Inserting a single row into a parent table cannot cause (or fix)
1030 ** an immediate foreign key violation. So do nothing in this case. */
1031 continue;
1032 }
1033
1034 if( sqlite3FkLocateIndex(pParse, pTab, pFKey, &pIdx, &aiCol) ){
1035 if( !isIgnoreErrors || db->mallocFailed ) return;
1036 continue;
1037 }
1038 assert( aiCol || pFKey->nCol==1 );
1039
1040 /* Create a SrcList structure containing the child table. We need the
1041 ** child table as a SrcList for sqlite3WhereBegin() */
1042 pSrc = sqlite3SrcListAppend(pParse, 0, 0, 0);
1043 if( pSrc ){
1044 SrcItem *pItem = pSrc->a;
1045 pItem->pTab = pFKey->pFrom;
1046 pItem->zName = pFKey->pFrom->zName;
1047 pItem->pTab->nTabRef++;
1048 pItem->iCursor = pParse->nTab++;
1049
1050 if( regNew!=0 ){
1051 fkScanChildren(pParse, pSrc, pTab, pIdx, pFKey, aiCol, regNew, -1);
1052 }
1053 if( regOld!=0 ){
1054 int eAction = pFKey->aAction[aChange!=0];
1055 fkScanChildren(pParse, pSrc, pTab, pIdx, pFKey, aiCol, regOld, 1);
1056 /* If this is a deferred FK constraint, or a CASCADE or SET NULL
1057 ** action applies, then any foreign key violations caused by
1058 ** removing the parent key will be rectified by the action trigger.
1059 ** So do not set the "may-abort" flag in this case.
1060 **
1061 ** Note 1: If the FK is declared "ON UPDATE CASCADE", then the
1062 ** may-abort flag will eventually be set on this statement anyway
1063 ** (when this function is called as part of processing the UPDATE
1064 ** within the action trigger).
1065 **
1066 ** Note 2: At first glance it may seem like SQLite could simply omit
1067 ** all OP_FkCounter related scans when either CASCADE or SET NULL
1068 ** applies. The trouble starts if the CASCADE or SET NULL action
1069 ** trigger causes other triggers or action rules attached to the
1070 ** child table to fire. In these cases the fk constraint counters
1071 ** might be set incorrectly if any OP_FkCounter related scans are
1072 ** omitted. */
1073 if( !pFKey->isDeferred && eAction!=OE_Cascade && eAction!=OE_SetNull ){
1074 sqlite3MayAbort(pParse);
1075 }
1076 }
1077 pItem->zName = 0;
1078 sqlite3SrcListDelete(db, pSrc);
1079 }
1080 sqlite3DbFree(db, aiCol);
1081 }
1082}
1083
1084#define COLUMN_MASK(x) (((x)>31) ? 0xffffffff : ((u32)1<<(x)))
1085
1086/*
1087** This function is called before generating code to update or delete a
1088** row contained in table pTab.
1089*/
1090u32 sqlite3FkOldmask(
1091 Parse *pParse, /* Parse context */
1092 Table *pTab /* Table being modified */
1093){
1094 u32 mask = 0;
1095 if( pParse->db->flags&SQLITE_ForeignKeys && IsOrdinaryTable(pTab) ){
1096 FKey *p;
1097 int i;
1098 for(p=pTab->u.tab.pFKey; p; p=p->pNextFrom){
1099 for(i=0; i<p->nCol; i++) mask |= COLUMN_MASK(p->aCol[i].iFrom);
1100 }
1101 for(p=sqlite3FkReferences(pTab); p; p=p->pNextTo){
1102 Index *pIdx = 0;
1103 sqlite3FkLocateIndex(pParse, pTab, p, &pIdx, 0);
1104 if( pIdx ){
1105 for(i=0; i<pIdx->nKeyCol; i++){
1106 assert( pIdx->aiColumn[i]>=0 );
1107 mask |= COLUMN_MASK(pIdx->aiColumn[i]);
1108 }
1109 }
1110 }
1111 }
1112 return mask;
1113}
1114
1115
1116/*
1117** This function is called before generating code to update or delete a
1118** row contained in table pTab. If the operation is a DELETE, then
1119** parameter aChange is passed a NULL value. For an UPDATE, aChange points
1120** to an array of size N, where N is the number of columns in table pTab.
1121** If the i'th column is not modified by the UPDATE, then the corresponding
1122** entry in the aChange[] array is set to -1. If the column is modified,
1123** the value is 0 or greater. Parameter chngRowid is set to true if the
1124** UPDATE statement modifies the rowid fields of the table.
1125**
1126** If any foreign key processing will be required, this function returns
1127** non-zero. If there is no foreign key related processing, this function
1128** returns zero.
1129**
1130** For an UPDATE, this function returns 2 if:
1131**
1132** * There are any FKs for which pTab is the child and the parent table
1133** and any FK processing at all is required (even of a different FK), or
1134**
1135** * the UPDATE modifies one or more parent keys for which the action is
1136** not "NO ACTION" (i.e. is CASCADE, SET DEFAULT or SET NULL).
1137**
1138** Or, assuming some other foreign key processing is required, 1.
1139*/
1140int sqlite3FkRequired(
1141 Parse *pParse, /* Parse context */
1142 Table *pTab, /* Table being modified */
1143 int *aChange, /* Non-NULL for UPDATE operations */
1144 int chngRowid /* True for UPDATE that affects rowid */
1145){
1146 int eRet = 1; /* Value to return if bHaveFK is true */
1147 int bHaveFK = 0; /* If FK processing is required */
1148 if( pParse->db->flags&SQLITE_ForeignKeys && IsOrdinaryTable(pTab) ){
1149 if( !aChange ){
1150 /* A DELETE operation. Foreign key processing is required if the
1151 ** table in question is either the child or parent table for any
1152 ** foreign key constraint. */
1153 bHaveFK = (sqlite3FkReferences(pTab) || pTab->u.tab.pFKey);
1154 }else{
1155 /* This is an UPDATE. Foreign key processing is only required if the
1156 ** operation modifies one or more child or parent key columns. */
1157 FKey *p;
1158
1159 /* Check if any child key columns are being modified. */
1160 for(p=pTab->u.tab.pFKey; p; p=p->pNextFrom){
1161 if( fkChildIsModified(pTab, p, aChange, chngRowid) ){
1162 if( 0==sqlite3_stricmp(pTab->zName, p->zTo) ) eRet = 2;
1163 bHaveFK = 1;
1164 }
1165 }
1166
1167 /* Check if any parent key columns are being modified. */
1168 for(p=sqlite3FkReferences(pTab); p; p=p->pNextTo){
1169 if( fkParentIsModified(pTab, p, aChange, chngRowid) ){
1170 if( p->aAction[1]!=OE_None ) return 2;
1171 bHaveFK = 1;
1172 }
1173 }
1174 }
1175 }
1176 return bHaveFK ? eRet : 0;
1177}
1178
1179/*
1180** This function is called when an UPDATE or DELETE operation is being
1181** compiled on table pTab, which is the parent table of foreign-key pFKey.
1182** If the current operation is an UPDATE, then the pChanges parameter is
1183** passed a pointer to the list of columns being modified. If it is a
1184** DELETE, pChanges is passed a NULL pointer.
1185**
1186** It returns a pointer to a Trigger structure containing a trigger
1187** equivalent to the ON UPDATE or ON DELETE action specified by pFKey.
1188** If the action is "NO ACTION" then a NULL pointer is returned (these actions
1189** require no special handling by the triggers sub-system, code for them is
1190** created by fkScanChildren()).
1191**
1192** For example, if pFKey is the foreign key and pTab is table "p" in
1193** the following schema:
1194**
1195** CREATE TABLE p(pk PRIMARY KEY);
1196** CREATE TABLE c(ck REFERENCES p ON DELETE CASCADE);
1197**
1198** then the returned trigger structure is equivalent to:
1199**
1200** CREATE TRIGGER ... DELETE ON p BEGIN
1201** DELETE FROM c WHERE ck = old.pk;
1202** END;
1203**
1204** The returned pointer is cached as part of the foreign key object. It
1205** is eventually freed along with the rest of the foreign key object by
1206** sqlite3FkDelete().
1207*/
1208static Trigger *fkActionTrigger(
1209 Parse *pParse, /* Parse context */
1210 Table *pTab, /* Table being updated or deleted from */
1211 FKey *pFKey, /* Foreign key to get action for */
1212 ExprList *pChanges /* Change-list for UPDATE, NULL for DELETE */
1213){
1214 sqlite3 *db = pParse->db; /* Database handle */
1215 int action; /* One of OE_None, OE_Cascade etc. */
1216 Trigger *pTrigger; /* Trigger definition to return */
1217 int iAction = (pChanges!=0); /* 1 for UPDATE, 0 for DELETE */
1218
1219 action = pFKey->aAction[iAction];
1220 if( action==OE_Restrict && (db->flags & SQLITE_DeferFKs) ){
1221 return 0;
1222 }
1223 pTrigger = pFKey->apTrigger[iAction];
1224
1225 if( action!=OE_None && !pTrigger ){
1226 char const *zFrom; /* Name of child table */
1227 int nFrom; /* Length in bytes of zFrom */
1228 Index *pIdx = 0; /* Parent key index for this FK */
1229 int *aiCol = 0; /* child table cols -> parent key cols */
1230 TriggerStep *pStep = 0; /* First (only) step of trigger program */
1231 Expr *pWhere = 0; /* WHERE clause of trigger step */
1232 ExprList *pList = 0; /* Changes list if ON UPDATE CASCADE */
1233 Select *pSelect = 0; /* If RESTRICT, "SELECT RAISE(...)" */
1234 int i; /* Iterator variable */
1235 Expr *pWhen = 0; /* WHEN clause for the trigger */
1236
1237 if( sqlite3FkLocateIndex(pParse, pTab, pFKey, &pIdx, &aiCol) ) return 0;
1238 assert( aiCol || pFKey->nCol==1 );
1239
1240 for(i=0; i<pFKey->nCol; i++){
1241 Token tOld = { "old", 3 }; /* Literal "old" token */
1242 Token tNew = { "new", 3 }; /* Literal "new" token */
1243 Token tFromCol; /* Name of column in child table */
1244 Token tToCol; /* Name of column in parent table */
1245 int iFromCol; /* Idx of column in child table */
1246 Expr *pEq; /* tFromCol = OLD.tToCol */
1247
1248 iFromCol = aiCol ? aiCol[i] : pFKey->aCol[0].iFrom;
1249 assert( iFromCol>=0 );
1250 assert( pIdx!=0 || (pTab->iPKey>=0 && pTab->iPKey<pTab->nCol) );
1251 assert( pIdx==0 || pIdx->aiColumn[i]>=0 );
1252 sqlite3TokenInit(&tToCol,
1253 pTab->aCol[pIdx ? pIdx->aiColumn[i] : pTab->iPKey].zCnName);
1254 sqlite3TokenInit(&tFromCol, pFKey->pFrom->aCol[iFromCol].zCnName);
1255
1256 /* Create the expression "OLD.zToCol = zFromCol". It is important
1257 ** that the "OLD.zToCol" term is on the LHS of the = operator, so
1258 ** that the affinity and collation sequence associated with the
1259 ** parent table are used for the comparison. */
1260 pEq = sqlite3PExpr(pParse, TK_EQ,
1261 sqlite3PExpr(pParse, TK_DOT,
1262 sqlite3ExprAlloc(db, TK_ID, &tOld, 0),
1263 sqlite3ExprAlloc(db, TK_ID, &tToCol, 0)),
1264 sqlite3ExprAlloc(db, TK_ID, &tFromCol, 0)
1265 );
1266 pWhere = sqlite3ExprAnd(pParse, pWhere, pEq);
1267
1268 /* For ON UPDATE, construct the next term of the WHEN clause.
1269 ** The final WHEN clause will be like this:
1270 **
1271 ** WHEN NOT(old.col1 IS new.col1 AND ... AND old.colN IS new.colN)
1272 */
1273 if( pChanges ){
1274 pEq = sqlite3PExpr(pParse, TK_IS,
1275 sqlite3PExpr(pParse, TK_DOT,
1276 sqlite3ExprAlloc(db, TK_ID, &tOld, 0),
1277 sqlite3ExprAlloc(db, TK_ID, &tToCol, 0)),
1278 sqlite3PExpr(pParse, TK_DOT,
1279 sqlite3ExprAlloc(db, TK_ID, &tNew, 0),
1280 sqlite3ExprAlloc(db, TK_ID, &tToCol, 0))
1281 );
1282 pWhen = sqlite3ExprAnd(pParse, pWhen, pEq);
1283 }
1284
1285 if( action!=OE_Restrict && (action!=OE_Cascade || pChanges) ){
1286 Expr *pNew;
1287 if( action==OE_Cascade ){
1288 pNew = sqlite3PExpr(pParse, TK_DOT,
1289 sqlite3ExprAlloc(db, TK_ID, &tNew, 0),
1290 sqlite3ExprAlloc(db, TK_ID, &tToCol, 0));
1291 }else if( action==OE_SetDflt ){
1292 Column *pCol = pFKey->pFrom->aCol + iFromCol;
1293 Expr *pDflt;
1294 if( pCol->colFlags & COLFLAG_GENERATED ){
1295 testcase( pCol->colFlags & COLFLAG_VIRTUAL );
1296 testcase( pCol->colFlags & COLFLAG_STORED );
1297 pDflt = 0;
1298 }else{
1299 pDflt = sqlite3ColumnExpr(pFKey->pFrom, pCol);
1300 }
1301 if( pDflt ){
1302 pNew = sqlite3ExprDup(db, pDflt, 0);
1303 }else{
1304 pNew = sqlite3ExprAlloc(db, TK_NULL, 0, 0);
1305 }
1306 }else{
1307 pNew = sqlite3ExprAlloc(db, TK_NULL, 0, 0);
1308 }
1309 pList = sqlite3ExprListAppend(pParse, pList, pNew);
1310 sqlite3ExprListSetName(pParse, pList, &tFromCol, 0);
1311 }
1312 }
1313 sqlite3DbFree(db, aiCol);
1314
1315 zFrom = pFKey->pFrom->zName;
1316 nFrom = sqlite3Strlen30(zFrom);
1317
1318 if( action==OE_Restrict ){
1319 int iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
1320 Token tFrom;
1321 Token tDb;
1322 Expr *pRaise;
1323
1324 tFrom.z = zFrom;
1325 tFrom.n = nFrom;
1326 tDb.z = db->aDb[iDb].zDbSName;
1327 tDb.n = sqlite3Strlen30(tDb.z);
1328
1329 pRaise = sqlite3Expr(db, TK_RAISE, "FOREIGN KEY constraint failed");
1330 if( pRaise ){
1331 pRaise->affExpr = OE_Abort;
1332 }
1333 pSelect = sqlite3SelectNew(pParse,
1334 sqlite3ExprListAppend(pParse, 0, pRaise),
1335 sqlite3SrcListAppend(pParse, 0, &tDb, &tFrom),
1336 pWhere,
1337 0, 0, 0, 0, 0
1338 );
1339 pWhere = 0;
1340 }
1341
1342 /* Disable lookaside memory allocation */
1343 DisableLookaside;
1344
1345 pTrigger = (Trigger *)sqlite3DbMallocZero(db,
1346 sizeof(Trigger) + /* struct Trigger */
1347 sizeof(TriggerStep) + /* Single step in trigger program */
1348 nFrom + 1 /* Space for pStep->zTarget */
1349 );
1350 if( pTrigger ){
1351 pStep = pTrigger->step_list = (TriggerStep *)&pTrigger[1];
1352 pStep->zTarget = (char *)&pStep[1];
1353 memcpy((char *)pStep->zTarget, zFrom, nFrom);
1354
1355 pStep->pWhere = sqlite3ExprDup(db, pWhere, EXPRDUP_REDUCE);
1356 pStep->pExprList = sqlite3ExprListDup(db, pList, EXPRDUP_REDUCE);
1357 pStep->pSelect = sqlite3SelectDup(db, pSelect, EXPRDUP_REDUCE);
1358 if( pWhen ){
1359 pWhen = sqlite3PExpr(pParse, TK_NOT, pWhen, 0);
1360 pTrigger->pWhen = sqlite3ExprDup(db, pWhen, EXPRDUP_REDUCE);
1361 }
1362 }
1363
1364 /* Re-enable the lookaside buffer, if it was disabled earlier. */
1365 EnableLookaside;
1366
1367 sqlite3ExprDelete(db, pWhere);
1368 sqlite3ExprDelete(db, pWhen);
1369 sqlite3ExprListDelete(db, pList);
1370 sqlite3SelectDelete(db, pSelect);
1371 if( db->mallocFailed==1 ){
1372 fkTriggerDelete(db, pTrigger);
1373 return 0;
1374 }
1375 assert( pStep!=0 );
1376 assert( pTrigger!=0 );
1377
1378 switch( action ){
1379 case OE_Restrict:
1380 pStep->op = TK_SELECT;
1381 break;
1382 case OE_Cascade:
1383 if( !pChanges ){
1384 pStep->op = TK_DELETE;
1385 break;
1386 }
1387 /* no break */ deliberate_fall_through
1388 default:
1389 pStep->op = TK_UPDATE;
1390 }
1391 pStep->pTrig = pTrigger;
1392 pTrigger->pSchema = pTab->pSchema;
1393 pTrigger->pTabSchema = pTab->pSchema;
1394 pFKey->apTrigger[iAction] = pTrigger;
1395 pTrigger->op = (pChanges ? TK_UPDATE : TK_DELETE);
1396 }
1397
1398 return pTrigger;
1399}
1400
1401/*
1402** This function is called when deleting or updating a row to implement
1403** any required CASCADE, SET NULL or SET DEFAULT actions.
1404*/
1405void sqlite3FkActions(
1406 Parse *pParse, /* Parse context */
1407 Table *pTab, /* Table being updated or deleted from */
1408 ExprList *pChanges, /* Change-list for UPDATE, NULL for DELETE */
1409 int regOld, /* Address of array containing old row */
1410 int *aChange, /* Array indicating UPDATEd columns (or 0) */
1411 int bChngRowid /* True if rowid is UPDATEd */
1412){
1413 /* If foreign-key support is enabled, iterate through all FKs that
1414 ** refer to table pTab. If there is an action associated with the FK
1415 ** for this operation (either update or delete), invoke the associated
1416 ** trigger sub-program. */
1417 if( pParse->db->flags&SQLITE_ForeignKeys ){
1418 FKey *pFKey; /* Iterator variable */
1419 for(pFKey = sqlite3FkReferences(pTab); pFKey; pFKey=pFKey->pNextTo){
1420 if( aChange==0 || fkParentIsModified(pTab, pFKey, aChange, bChngRowid) ){
1421 Trigger *pAct = fkActionTrigger(pParse, pTab, pFKey, pChanges);
1422 if( pAct ){
1423 sqlite3CodeRowTriggerDirect(pParse, pAct, pTab, regOld, OE_Abort, 0);
1424 }
1425 }
1426 }
1427 }
1428}
1429
1430#endif /* ifndef SQLITE_OMIT_TRIGGER */
1431
1432/*
1433** Free all memory associated with foreign key definitions attached to
1434** table pTab. Remove the deleted foreign keys from the Schema.fkeyHash
1435** hash table.
1436*/
1437void sqlite3FkDelete(sqlite3 *db, Table *pTab){
1438 FKey *pFKey; /* Iterator variable */
1439 FKey *pNext; /* Copy of pFKey->pNextFrom */
1440
1441 assert( IsOrdinaryTable(pTab) );
1442 assert( db!=0 );
1443 for(pFKey=pTab->u.tab.pFKey; pFKey; pFKey=pNext){
1444 assert( db==0 || sqlite3SchemaMutexHeld(db, 0, pTab->pSchema) );
1445
1446 /* Remove the FK from the fkeyHash hash table. */
1447 if( db->pnBytesFreed==0 ){
1448 if( pFKey->pPrevTo ){
1449 pFKey->pPrevTo->pNextTo = pFKey->pNextTo;
1450 }else{
1451 void *p = (void *)pFKey->pNextTo;
1452 const char *z = (p ? pFKey->pNextTo->zTo : pFKey->zTo);
1453 sqlite3HashInsert(&pTab->pSchema->fkeyHash, z, p);
1454 }
1455 if( pFKey->pNextTo ){
1456 pFKey->pNextTo->pPrevTo = pFKey->pPrevTo;
1457 }
1458 }
1459
1460 /* EV: R-30323-21917 Each foreign key constraint in SQLite is
1461 ** classified as either immediate or deferred.
1462 */
1463 assert( pFKey->isDeferred==0 || pFKey->isDeferred==1 );
1464
1465 /* Delete any triggers created to implement actions for this FK. */
1466#ifndef SQLITE_OMIT_TRIGGER
1467 fkTriggerDelete(db, pFKey->apTrigger[0]);
1468 fkTriggerDelete(db, pFKey->apTrigger[1]);
1469#endif
1470
1471 pNext = pFKey->pNextFrom;
1472 sqlite3DbFree(db, pFKey);
1473 }
1474}
1475#endif /* ifndef SQLITE_OMIT_FOREIGN_KEY */
1476