000001 /*
000002 **
000003 ** The author disclaims copyright to this source code. In place of
000004 ** a legal notice, here is a blessing:
000005 **
000006 ** May you do good and not evil.
000007 ** May you find forgiveness for yourself and forgive others.
000008 ** May you share freely, never taking more than you give.
000009 **
000010 *************************************************************************
000011 ** This file contains code used by the compiler to add foreign key
000012 ** support to compiled SQL statements.
000013 */
000014 #include "sqliteInt.h"
000015
000016 #ifndef SQLITE_OMIT_FOREIGN_KEY
000017 #ifndef SQLITE_OMIT_TRIGGER
000018
000019 /*
000020 ** Deferred and Immediate FKs
000021 ** --------------------------
000022 **
000023 ** Foreign keys in SQLite come in two flavours: deferred and immediate.
000024 ** If an immediate foreign key constraint is violated,
000025 ** SQLITE_CONSTRAINT_FOREIGNKEY is returned and the current
000026 ** statement transaction rolled back. If a
000027 ** deferred foreign key constraint is violated, no action is taken
000028 ** immediately. However if the application attempts to commit the
000029 ** transaction before fixing the constraint violation, the attempt fails.
000030 **
000031 ** Deferred constraints are implemented using a simple counter associated
000032 ** with the database handle. The counter is set to zero each time a
000033 ** database transaction is opened. Each time a statement is executed
000034 ** that causes a foreign key violation, the counter is incremented. Each
000035 ** time a statement is executed that removes an existing violation from
000036 ** the database, the counter is decremented. When the transaction is
000037 ** committed, the commit fails if the current value of the counter is
000038 ** greater than zero. This scheme has two big drawbacks:
000039 **
000040 ** * When a commit fails due to a deferred foreign key constraint,
000041 ** there is no way to tell which foreign constraint is not satisfied,
000042 ** or which row it is not satisfied for.
000043 **
000044 ** * If the database contains foreign key violations when the
000045 ** transaction is opened, this may cause the mechanism to malfunction.
000046 **
000047 ** Despite these problems, this approach is adopted as it seems simpler
000048 ** than the alternatives.
000049 **
000050 ** INSERT operations:
000051 **
000052 ** I.1) For each FK for which the table is the child table, search
000053 ** the parent table for a match. If none is found increment the
000054 ** constraint counter.
000055 **
000056 ** I.2) For each FK for which the table is the parent table,
000057 ** search the child table for rows that correspond to the new
000058 ** row in the parent table. Decrement the counter for each row
000059 ** found (as the constraint is now satisfied).
000060 **
000061 ** DELETE operations:
000062 **
000063 ** D.1) For each FK for which the table is the child table,
000064 ** search the parent table for a row that corresponds to the
000065 ** deleted row in the child table. If such a row is not found,
000066 ** decrement the counter.
000067 **
000068 ** D.2) For each FK for which the table is the parent table, search
000069 ** the child table for rows that correspond to the deleted row
000070 ** in the parent table. For each found increment the counter.
000071 **
000072 ** UPDATE operations:
000073 **
000074 ** An UPDATE command requires that all 4 steps above are taken, but only
000075 ** for FK constraints for which the affected columns are actually
000076 ** modified (values must be compared at runtime).
000077 **
000078 ** Note that I.1 and D.1 are very similar operations, as are I.2 and D.2.
000079 ** This simplifies the implementation a bit.
000080 **
000081 ** For the purposes of immediate FK constraints, the OR REPLACE conflict
000082 ** resolution is considered to delete rows before the new row is inserted.
000083 ** If a delete caused by OR REPLACE violates an FK constraint, an exception
000084 ** is thrown, even if the FK constraint would be satisfied after the new
000085 ** row is inserted.
000086 **
000087 ** Immediate constraints are usually handled similarly. The only difference
000088 ** is that the counter used is stored as part of each individual statement
000089 ** object (struct Vdbe). If, after the statement has run, its immediate
000090 ** constraint counter is greater than zero,
000091 ** it returns SQLITE_CONSTRAINT_FOREIGNKEY
000092 ** and the statement transaction is rolled back. An exception is an INSERT
000093 ** statement that inserts a single row only (no triggers). In this case,
000094 ** instead of using a counter, an exception is thrown immediately if the
000095 ** INSERT violates a foreign key constraint. This is necessary as such
000096 ** an INSERT does not open a statement transaction.
000097 **
000098 ** TODO: How should dropping a table be handled? How should renaming a
000099 ** table be handled?
000100 **
000101 **
000102 ** Query API Notes
000103 ** ---------------
000104 **
000105 ** Before coding an UPDATE or DELETE row operation, the code-generator
000106 ** for those two operations needs to know whether or not the operation
000107 ** requires any FK processing and, if so, which columns of the original
000108 ** row are required by the FK processing VDBE code (i.e. if FKs were
000109 ** implemented using triggers, which of the old.* columns would be
000110 ** accessed). No information is required by the code-generator before
000111 ** coding an INSERT operation. The functions used by the UPDATE/DELETE
000112 ** generation code to query for this information are:
000113 **
000114 ** sqlite3FkRequired() - Test to see if FK processing is required.
000115 ** sqlite3FkOldmask() - Query for the set of required old.* columns.
000116 **
000117 **
000118 ** Externally accessible module functions
000119 ** --------------------------------------
000120 **
000121 ** sqlite3FkCheck() - Check for foreign key violations.
000122 ** sqlite3FkActions() - Code triggers for ON UPDATE/ON DELETE actions.
000123 ** sqlite3FkDelete() - Delete an FKey structure.
000124 */
000125
000126 /*
000127 ** VDBE Calling Convention
000128 ** -----------------------
000129 **
000130 ** Example:
000131 **
000132 ** For the following INSERT statement:
000133 **
000134 ** CREATE TABLE t1(a, b INTEGER PRIMARY KEY, c);
000135 ** INSERT INTO t1 VALUES(1, 2, 3.1);
000136 **
000137 ** Register (x): 2 (type integer)
000138 ** Register (x+1): 1 (type integer)
000139 ** Register (x+2): NULL (type NULL)
000140 ** Register (x+3): 3.1 (type real)
000141 */
000142
000143 /*
000144 ** A foreign key constraint requires that the key columns in the parent
000145 ** table are collectively subject to a UNIQUE or PRIMARY KEY constraint.
000146 ** Given that pParent is the parent table for foreign key constraint pFKey,
000147 ** search the schema for a unique index on the parent key columns.
000148 **
000149 ** If successful, zero is returned. If the parent key is an INTEGER PRIMARY
000150 ** KEY column, then output variable *ppIdx is set to NULL. Otherwise, *ppIdx
000151 ** is set to point to the unique index.
000152 **
000153 ** If the parent key consists of a single column (the foreign key constraint
000154 ** is not a composite foreign key), output variable *paiCol is set to NULL.
000155 ** Otherwise, it is set to point to an allocated array of size N, where
000156 ** N is the number of columns in the parent key. The first element of the
000157 ** array is the index of the child table column that is mapped by the FK
000158 ** constraint to the parent table column stored in the left-most column
000159 ** of index *ppIdx. The second element of the array is the index of the
000160 ** child table column that corresponds to the second left-most column of
000161 ** *ppIdx, and so on.
000162 **
000163 ** If the required index cannot be found, either because:
000164 **
000165 ** 1) The named parent key columns do not exist, or
000166 **
000167 ** 2) The named parent key columns do exist, but are not subject to a
000168 ** UNIQUE or PRIMARY KEY constraint, or
000169 **
000170 ** 3) No parent key columns were provided explicitly as part of the
000171 ** foreign key definition, and the parent table does not have a
000172 ** PRIMARY KEY, or
000173 **
000174 ** 4) No parent key columns were provided explicitly as part of the
000175 ** foreign key definition, and the PRIMARY KEY of the parent table
000176 ** consists of a different number of columns to the child key in
000177 ** the child table.
000178 **
000179 ** then non-zero is returned, and a "foreign key mismatch" error loaded
000180 ** into pParse. If an OOM error occurs, non-zero is returned and the
000181 ** pParse->db->mallocFailed flag is set.
000182 */
000183 int sqlite3FkLocateIndex(
000184 Parse *pParse, /* Parse context to store any error in */
000185 Table *pParent, /* Parent table of FK constraint pFKey */
000186 FKey *pFKey, /* Foreign key to find index for */
000187 Index **ppIdx, /* OUT: Unique index on parent table */
000188 int **paiCol /* OUT: Map of index columns in pFKey */
000189 ){
000190 Index *pIdx = 0; /* Value to return via *ppIdx */
000191 int *aiCol = 0; /* Value to return via *paiCol */
000192 int nCol = pFKey->nCol; /* Number of columns in parent key */
000193 char *zKey = pFKey->aCol[0].zCol; /* Name of left-most parent key column */
000194
000195 /* The caller is responsible for zeroing output parameters. */
000196 assert( ppIdx && *ppIdx==0 );
000197 assert( !paiCol || *paiCol==0 );
000198 assert( pParse );
000199
000200 /* If this is a non-composite (single column) foreign key, check if it
000201 ** maps to the INTEGER PRIMARY KEY of table pParent. If so, leave *ppIdx
000202 ** and *paiCol set to zero and return early.
000203 **
000204 ** Otherwise, for a composite foreign key (more than one column), allocate
000205 ** space for the aiCol array (returned via output parameter *paiCol).
000206 ** Non-composite foreign keys do not require the aiCol array.
000207 */
000208 if( nCol==1 ){
000209 /* The FK maps to the IPK if any of the following are true:
000210 **
000211 ** 1) There is an INTEGER PRIMARY KEY column and the FK is implicitly
000212 ** mapped to the primary key of table pParent, or
000213 ** 2) The FK is explicitly mapped to a column declared as INTEGER
000214 ** PRIMARY KEY.
000215 */
000216 if( pParent->iPKey>=0 ){
000217 if( !zKey ) return 0;
000218 if( !sqlite3StrICmp(pParent->aCol[pParent->iPKey].zName, zKey) ) return 0;
000219 }
000220 }else if( paiCol ){
000221 assert( nCol>1 );
000222 aiCol = (int *)sqlite3DbMallocRawNN(pParse->db, nCol*sizeof(int));
000223 if( !aiCol ) return 1;
000224 *paiCol = aiCol;
000225 }
000226
000227 for(pIdx=pParent->pIndex; pIdx; pIdx=pIdx->pNext){
000228 if( pIdx->nKeyCol==nCol && IsUniqueIndex(pIdx) && pIdx->pPartIdxWhere==0 ){
000229 /* pIdx is a UNIQUE index (or a PRIMARY KEY) and has the right number
000230 ** of columns. If each indexed column corresponds to a foreign key
000231 ** column of pFKey, then this index is a winner. */
000232
000233 if( zKey==0 ){
000234 /* If zKey is NULL, then this foreign key is implicitly mapped to
000235 ** the PRIMARY KEY of table pParent. The PRIMARY KEY index may be
000236 ** identified by the test. */
000237 if( IsPrimaryKeyIndex(pIdx) ){
000238 if( aiCol ){
000239 int i;
000240 for(i=0; i<nCol; i++) aiCol[i] = pFKey->aCol[i].iFrom;
000241 }
000242 break;
000243 }
000244 }else{
000245 /* If zKey is non-NULL, then this foreign key was declared to
000246 ** map to an explicit list of columns in table pParent. Check if this
000247 ** index matches those columns. Also, check that the index uses
000248 ** the default collation sequences for each column. */
000249 int i, j;
000250 for(i=0; i<nCol; i++){
000251 i16 iCol = pIdx->aiColumn[i]; /* Index of column in parent tbl */
000252 const char *zDfltColl; /* Def. collation for column */
000253 char *zIdxCol; /* Name of indexed column */
000254
000255 if( iCol<0 ) break; /* No foreign keys against expression indexes */
000256
000257 /* If the index uses a collation sequence that is different from
000258 ** the default collation sequence for the column, this index is
000259 ** unusable. Bail out early in this case. */
000260 zDfltColl = pParent->aCol[iCol].zColl;
000261 if( !zDfltColl ) zDfltColl = sqlite3StrBINARY;
000262 if( sqlite3StrICmp(pIdx->azColl[i], zDfltColl) ) break;
000263
000264 zIdxCol = pParent->aCol[iCol].zName;
000265 for(j=0; j<nCol; j++){
000266 if( sqlite3StrICmp(pFKey->aCol[j].zCol, zIdxCol)==0 ){
000267 if( aiCol ) aiCol[i] = pFKey->aCol[j].iFrom;
000268 break;
000269 }
000270 }
000271 if( j==nCol ) break;
000272 }
000273 if( i==nCol ) break; /* pIdx is usable */
000274 }
000275 }
000276 }
000277
000278 if( !pIdx ){
000279 if( !pParse->disableTriggers ){
000280 sqlite3ErrorMsg(pParse,
000281 "foreign key mismatch - \"%w\" referencing \"%w\"",
000282 pFKey->pFrom->zName, pFKey->zTo);
000283 }
000284 sqlite3DbFree(pParse->db, aiCol);
000285 return 1;
000286 }
000287
000288 *ppIdx = pIdx;
000289 return 0;
000290 }
000291
000292 /*
000293 ** This function is called when a row is inserted into or deleted from the
000294 ** child table of foreign key constraint pFKey. If an SQL UPDATE is executed
000295 ** on the child table of pFKey, this function is invoked twice for each row
000296 ** affected - once to "delete" the old row, and then again to "insert" the
000297 ** new row.
000298 **
000299 ** Each time it is called, this function generates VDBE code to locate the
000300 ** row in the parent table that corresponds to the row being inserted into
000301 ** or deleted from the child table. If the parent row can be found, no
000302 ** special action is taken. Otherwise, if the parent row can *not* be
000303 ** found in the parent table:
000304 **
000305 ** Operation | FK type | Action taken
000306 ** --------------------------------------------------------------------------
000307 ** INSERT immediate Increment the "immediate constraint counter".
000308 **
000309 ** DELETE immediate Decrement the "immediate constraint counter".
000310 **
000311 ** INSERT deferred Increment the "deferred constraint counter".
000312 **
000313 ** DELETE deferred Decrement the "deferred constraint counter".
000314 **
000315 ** These operations are identified in the comment at the top of this file
000316 ** (fkey.c) as "I.1" and "D.1".
000317 */
000318 static void fkLookupParent(
000319 Parse *pParse, /* Parse context */
000320 int iDb, /* Index of database housing pTab */
000321 Table *pTab, /* Parent table of FK pFKey */
000322 Index *pIdx, /* Unique index on parent key columns in pTab */
000323 FKey *pFKey, /* Foreign key constraint */
000324 int *aiCol, /* Map from parent key columns to child table columns */
000325 int regData, /* Address of array containing child table row */
000326 int nIncr, /* Increment constraint counter by this */
000327 int isIgnore /* If true, pretend pTab contains all NULL values */
000328 ){
000329 int i; /* Iterator variable */
000330 Vdbe *v = sqlite3GetVdbe(pParse); /* Vdbe to add code to */
000331 int iCur = pParse->nTab - 1; /* Cursor number to use */
000332 int iOk = sqlite3VdbeMakeLabel(v); /* jump here if parent key found */
000333
000334 /* If nIncr is less than zero, then check at runtime if there are any
000335 ** outstanding constraints to resolve. If there are not, there is no need
000336 ** to check if deleting this row resolves any outstanding violations.
000337 **
000338 ** Check if any of the key columns in the child table row are NULL. If
000339 ** any are, then the constraint is considered satisfied. No need to
000340 ** search for a matching row in the parent table. */
000341 if( nIncr<0 ){
000342 sqlite3VdbeAddOp2(v, OP_FkIfZero, pFKey->isDeferred, iOk);
000343 VdbeCoverage(v);
000344 }
000345 for(i=0; i<pFKey->nCol; i++){
000346 int iReg = aiCol[i] + regData + 1;
000347 sqlite3VdbeAddOp2(v, OP_IsNull, iReg, iOk); VdbeCoverage(v);
000348 }
000349
000350 if( isIgnore==0 ){
000351 if( pIdx==0 ){
000352 /* If pIdx is NULL, then the parent key is the INTEGER PRIMARY KEY
000353 ** column of the parent table (table pTab). */
000354 int iMustBeInt; /* Address of MustBeInt instruction */
000355 int regTemp = sqlite3GetTempReg(pParse);
000356
000357 /* Invoke MustBeInt to coerce the child key value to an integer (i.e.
000358 ** apply the affinity of the parent key). If this fails, then there
000359 ** is no matching parent key. Before using MustBeInt, make a copy of
000360 ** the value. Otherwise, the value inserted into the child key column
000361 ** will have INTEGER affinity applied to it, which may not be correct. */
000362 sqlite3VdbeAddOp2(v, OP_SCopy, aiCol[0]+1+regData, regTemp);
000363 iMustBeInt = sqlite3VdbeAddOp2(v, OP_MustBeInt, regTemp, 0);
000364 VdbeCoverage(v);
000365
000366 /* If the parent table is the same as the child table, and we are about
000367 ** to increment the constraint-counter (i.e. this is an INSERT operation),
000368 ** then check if the row being inserted matches itself. If so, do not
000369 ** increment the constraint-counter. */
000370 if( pTab==pFKey->pFrom && nIncr==1 ){
000371 sqlite3VdbeAddOp3(v, OP_Eq, regData, iOk, regTemp); VdbeCoverage(v);
000372 sqlite3VdbeChangeP5(v, SQLITE_NOTNULL);
000373 }
000374
000375 sqlite3OpenTable(pParse, iCur, iDb, pTab, OP_OpenRead);
000376 sqlite3VdbeAddOp3(v, OP_NotExists, iCur, 0, regTemp); VdbeCoverage(v);
000377 sqlite3VdbeGoto(v, iOk);
000378 sqlite3VdbeJumpHere(v, sqlite3VdbeCurrentAddr(v)-2);
000379 sqlite3VdbeJumpHere(v, iMustBeInt);
000380 sqlite3ReleaseTempReg(pParse, regTemp);
000381 }else{
000382 int nCol = pFKey->nCol;
000383 int regTemp = sqlite3GetTempRange(pParse, nCol);
000384 int regRec = sqlite3GetTempReg(pParse);
000385
000386 sqlite3VdbeAddOp3(v, OP_OpenRead, iCur, pIdx->tnum, iDb);
000387 sqlite3VdbeSetP4KeyInfo(pParse, pIdx);
000388 for(i=0; i<nCol; i++){
000389 sqlite3VdbeAddOp2(v, OP_Copy, aiCol[i]+1+regData, regTemp+i);
000390 }
000391
000392 /* If the parent table is the same as the child table, and we are about
000393 ** to increment the constraint-counter (i.e. this is an INSERT operation),
000394 ** then check if the row being inserted matches itself. If so, do not
000395 ** increment the constraint-counter.
000396 **
000397 ** If any of the parent-key values are NULL, then the row cannot match
000398 ** itself. So set JUMPIFNULL to make sure we do the OP_Found if any
000399 ** of the parent-key values are NULL (at this point it is known that
000400 ** none of the child key values are).
000401 */
000402 if( pTab==pFKey->pFrom && nIncr==1 ){
000403 int iJump = sqlite3VdbeCurrentAddr(v) + nCol + 1;
000404 for(i=0; i<nCol; i++){
000405 int iChild = aiCol[i]+1+regData;
000406 int iParent = pIdx->aiColumn[i]+1+regData;
000407 assert( pIdx->aiColumn[i]>=0 );
000408 assert( aiCol[i]!=pTab->iPKey );
000409 if( pIdx->aiColumn[i]==pTab->iPKey ){
000410 /* The parent key is a composite key that includes the IPK column */
000411 iParent = regData;
000412 }
000413 sqlite3VdbeAddOp3(v, OP_Ne, iChild, iJump, iParent); VdbeCoverage(v);
000414 sqlite3VdbeChangeP5(v, SQLITE_JUMPIFNULL);
000415 }
000416 sqlite3VdbeGoto(v, iOk);
000417 }
000418
000419 sqlite3VdbeAddOp4(v, OP_MakeRecord, regTemp, nCol, regRec,
000420 sqlite3IndexAffinityStr(pParse->db,pIdx), nCol);
000421 sqlite3VdbeAddOp4Int(v, OP_Found, iCur, iOk, regRec, 0); VdbeCoverage(v);
000422
000423 sqlite3ReleaseTempReg(pParse, regRec);
000424 sqlite3ReleaseTempRange(pParse, regTemp, nCol);
000425 }
000426 }
000427
000428 if( !pFKey->isDeferred && !(pParse->db->flags & SQLITE_DeferFKs)
000429 && !pParse->pToplevel
000430 && !pParse->isMultiWrite
000431 ){
000432 /* Special case: If this is an INSERT statement that will insert exactly
000433 ** one row into the table, raise a constraint immediately instead of
000434 ** incrementing a counter. This is necessary as the VM code is being
000435 ** generated for will not open a statement transaction. */
000436 assert( nIncr==1 );
000437 sqlite3HaltConstraint(pParse, SQLITE_CONSTRAINT_FOREIGNKEY,
000438 OE_Abort, 0, P4_STATIC, P5_ConstraintFK);
000439 }else{
000440 if( nIncr>0 && pFKey->isDeferred==0 ){
000441 sqlite3MayAbort(pParse);
000442 }
000443 sqlite3VdbeAddOp2(v, OP_FkCounter, pFKey->isDeferred, nIncr);
000444 }
000445
000446 sqlite3VdbeResolveLabel(v, iOk);
000447 sqlite3VdbeAddOp1(v, OP_Close, iCur);
000448 }
000449
000450
000451 /*
000452 ** Return an Expr object that refers to a memory register corresponding
000453 ** to column iCol of table pTab.
000454 **
000455 ** regBase is the first of an array of register that contains the data
000456 ** for pTab. regBase itself holds the rowid. regBase+1 holds the first
000457 ** column. regBase+2 holds the second column, and so forth.
000458 */
000459 static Expr *exprTableRegister(
000460 Parse *pParse, /* Parsing and code generating context */
000461 Table *pTab, /* The table whose content is at r[regBase]... */
000462 int regBase, /* Contents of table pTab */
000463 i16 iCol /* Which column of pTab is desired */
000464 ){
000465 Expr *pExpr;
000466 Column *pCol;
000467 const char *zColl;
000468 sqlite3 *db = pParse->db;
000469
000470 pExpr = sqlite3Expr(db, TK_REGISTER, 0);
000471 if( pExpr ){
000472 if( iCol>=0 && iCol!=pTab->iPKey ){
000473 pCol = &pTab->aCol[iCol];
000474 pExpr->iTable = regBase + iCol + 1;
000475 pExpr->affinity = pCol->affinity;
000476 zColl = pCol->zColl;
000477 if( zColl==0 ) zColl = db->pDfltColl->zName;
000478 pExpr = sqlite3ExprAddCollateString(pParse, pExpr, zColl);
000479 }else{
000480 pExpr->iTable = regBase;
000481 pExpr->affinity = SQLITE_AFF_INTEGER;
000482 }
000483 }
000484 return pExpr;
000485 }
000486
000487 /*
000488 ** Return an Expr object that refers to column iCol of table pTab which
000489 ** has cursor iCur.
000490 */
000491 static Expr *exprTableColumn(
000492 sqlite3 *db, /* The database connection */
000493 Table *pTab, /* The table whose column is desired */
000494 int iCursor, /* The open cursor on the table */
000495 i16 iCol /* The column that is wanted */
000496 ){
000497 Expr *pExpr = sqlite3Expr(db, TK_COLUMN, 0);
000498 if( pExpr ){
000499 pExpr->pTab = pTab;
000500 pExpr->iTable = iCursor;
000501 pExpr->iColumn = iCol;
000502 }
000503 return pExpr;
000504 }
000505
000506 /*
000507 ** This function is called to generate code executed when a row is deleted
000508 ** from the parent table of foreign key constraint pFKey and, if pFKey is
000509 ** deferred, when a row is inserted into the same table. When generating
000510 ** code for an SQL UPDATE operation, this function may be called twice -
000511 ** once to "delete" the old row and once to "insert" the new row.
000512 **
000513 ** Parameter nIncr is passed -1 when inserting a row (as this may decrease
000514 ** the number of FK violations in the db) or +1 when deleting one (as this
000515 ** may increase the number of FK constraint problems).
000516 **
000517 ** The code generated by this function scans through the rows in the child
000518 ** table that correspond to the parent table row being deleted or inserted.
000519 ** For each child row found, one of the following actions is taken:
000520 **
000521 ** Operation | FK type | Action taken
000522 ** --------------------------------------------------------------------------
000523 ** DELETE immediate Increment the "immediate constraint counter".
000524 ** Or, if the ON (UPDATE|DELETE) action is RESTRICT,
000525 ** throw a "FOREIGN KEY constraint failed" exception.
000526 **
000527 ** INSERT immediate Decrement the "immediate constraint counter".
000528 **
000529 ** DELETE deferred Increment the "deferred constraint counter".
000530 ** Or, if the ON (UPDATE|DELETE) action is RESTRICT,
000531 ** throw a "FOREIGN KEY constraint failed" exception.
000532 **
000533 ** INSERT deferred Decrement the "deferred constraint counter".
000534 **
000535 ** These operations are identified in the comment at the top of this file
000536 ** (fkey.c) as "I.2" and "D.2".
000537 */
000538 static void fkScanChildren(
000539 Parse *pParse, /* Parse context */
000540 SrcList *pSrc, /* The child table to be scanned */
000541 Table *pTab, /* The parent table */
000542 Index *pIdx, /* Index on parent covering the foreign key */
000543 FKey *pFKey, /* The foreign key linking pSrc to pTab */
000544 int *aiCol, /* Map from pIdx cols to child table cols */
000545 int regData, /* Parent row data starts here */
000546 int nIncr /* Amount to increment deferred counter by */
000547 ){
000548 sqlite3 *db = pParse->db; /* Database handle */
000549 int i; /* Iterator variable */
000550 Expr *pWhere = 0; /* WHERE clause to scan with */
000551 NameContext sNameContext; /* Context used to resolve WHERE clause */
000552 WhereInfo *pWInfo; /* Context used by sqlite3WhereXXX() */
000553 int iFkIfZero = 0; /* Address of OP_FkIfZero */
000554 Vdbe *v = sqlite3GetVdbe(pParse);
000555
000556 assert( pIdx==0 || pIdx->pTable==pTab );
000557 assert( pIdx==0 || pIdx->nKeyCol==pFKey->nCol );
000558 assert( pIdx!=0 || pFKey->nCol==1 );
000559 assert( pIdx!=0 || HasRowid(pTab) );
000560
000561 if( nIncr<0 ){
000562 iFkIfZero = sqlite3VdbeAddOp2(v, OP_FkIfZero, pFKey->isDeferred, 0);
000563 VdbeCoverage(v);
000564 }
000565
000566 /* Create an Expr object representing an SQL expression like:
000567 **
000568 ** <parent-key1> = <child-key1> AND <parent-key2> = <child-key2> ...
000569 **
000570 ** The collation sequence used for the comparison should be that of
000571 ** the parent key columns. The affinity of the parent key column should
000572 ** be applied to each child key value before the comparison takes place.
000573 */
000574 for(i=0; i<pFKey->nCol; i++){
000575 Expr *pLeft; /* Value from parent table row */
000576 Expr *pRight; /* Column ref to child table */
000577 Expr *pEq; /* Expression (pLeft = pRight) */
000578 i16 iCol; /* Index of column in child table */
000579 const char *zCol; /* Name of column in child table */
000580
000581 iCol = pIdx ? pIdx->aiColumn[i] : -1;
000582 pLeft = exprTableRegister(pParse, pTab, regData, iCol);
000583 iCol = aiCol ? aiCol[i] : pFKey->aCol[0].iFrom;
000584 assert( iCol>=0 );
000585 zCol = pFKey->pFrom->aCol[iCol].zName;
000586 pRight = sqlite3Expr(db, TK_ID, zCol);
000587 pEq = sqlite3PExpr(pParse, TK_EQ, pLeft, pRight);
000588 pWhere = sqlite3ExprAnd(db, pWhere, pEq);
000589 }
000590
000591 /* If the child table is the same as the parent table, then add terms
000592 ** to the WHERE clause that prevent this entry from being scanned.
000593 ** The added WHERE clause terms are like this:
000594 **
000595 ** $current_rowid!=rowid
000596 ** NOT( $current_a==a AND $current_b==b AND ... )
000597 **
000598 ** The first form is used for rowid tables. The second form is used
000599 ** for WITHOUT ROWID tables. In the second form, the primary key is
000600 ** (a,b,...)
000601 */
000602 if( pTab==pFKey->pFrom && nIncr>0 ){
000603 Expr *pNe; /* Expression (pLeft != pRight) */
000604 Expr *pLeft; /* Value from parent table row */
000605 Expr *pRight; /* Column ref to child table */
000606 if( HasRowid(pTab) ){
000607 pLeft = exprTableRegister(pParse, pTab, regData, -1);
000608 pRight = exprTableColumn(db, pTab, pSrc->a[0].iCursor, -1);
000609 pNe = sqlite3PExpr(pParse, TK_NE, pLeft, pRight);
000610 }else{
000611 Expr *pEq, *pAll = 0;
000612 Index *pPk = sqlite3PrimaryKeyIndex(pTab);
000613 assert( pIdx!=0 );
000614 for(i=0; i<pPk->nKeyCol; i++){
000615 i16 iCol = pIdx->aiColumn[i];
000616 assert( iCol>=0 );
000617 pLeft = exprTableRegister(pParse, pTab, regData, iCol);
000618 pRight = exprTableColumn(db, pTab, pSrc->a[0].iCursor, iCol);
000619 pEq = sqlite3PExpr(pParse, TK_EQ, pLeft, pRight);
000620 pAll = sqlite3ExprAnd(db, pAll, pEq);
000621 }
000622 pNe = sqlite3PExpr(pParse, TK_NOT, pAll, 0);
000623 }
000624 pWhere = sqlite3ExprAnd(db, pWhere, pNe);
000625 }
000626
000627 /* Resolve the references in the WHERE clause. */
000628 memset(&sNameContext, 0, sizeof(NameContext));
000629 sNameContext.pSrcList = pSrc;
000630 sNameContext.pParse = pParse;
000631 sqlite3ResolveExprNames(&sNameContext, pWhere);
000632
000633 /* Create VDBE to loop through the entries in pSrc that match the WHERE
000634 ** clause. For each row found, increment either the deferred or immediate
000635 ** foreign key constraint counter. */
000636 pWInfo = sqlite3WhereBegin(pParse, pSrc, pWhere, 0, 0, 0, 0);
000637 sqlite3VdbeAddOp2(v, OP_FkCounter, pFKey->isDeferred, nIncr);
000638 if( pWInfo ){
000639 sqlite3WhereEnd(pWInfo);
000640 }
000641
000642 /* Clean up the WHERE clause constructed above. */
000643 sqlite3ExprDelete(db, pWhere);
000644 if( iFkIfZero ){
000645 sqlite3VdbeJumpHere(v, iFkIfZero);
000646 }
000647 }
000648
000649 /*
000650 ** This function returns a linked list of FKey objects (connected by
000651 ** FKey.pNextTo) holding all children of table pTab. For example,
000652 ** given the following schema:
000653 **
000654 ** CREATE TABLE t1(a PRIMARY KEY);
000655 ** CREATE TABLE t2(b REFERENCES t1(a);
000656 **
000657 ** Calling this function with table "t1" as an argument returns a pointer
000658 ** to the FKey structure representing the foreign key constraint on table
000659 ** "t2". Calling this function with "t2" as the argument would return a
000660 ** NULL pointer (as there are no FK constraints for which t2 is the parent
000661 ** table).
000662 */
000663 FKey *sqlite3FkReferences(Table *pTab){
000664 return (FKey *)sqlite3HashFind(&pTab->pSchema->fkeyHash, pTab->zName);
000665 }
000666
000667 /*
000668 ** The second argument is a Trigger structure allocated by the
000669 ** fkActionTrigger() routine. This function deletes the Trigger structure
000670 ** and all of its sub-components.
000671 **
000672 ** The Trigger structure or any of its sub-components may be allocated from
000673 ** the lookaside buffer belonging to database handle dbMem.
000674 */
000675 static void fkTriggerDelete(sqlite3 *dbMem, Trigger *p){
000676 if( p ){
000677 TriggerStep *pStep = p->step_list;
000678 sqlite3ExprDelete(dbMem, pStep->pWhere);
000679 sqlite3ExprListDelete(dbMem, pStep->pExprList);
000680 sqlite3SelectDelete(dbMem, pStep->pSelect);
000681 sqlite3ExprDelete(dbMem, p->pWhen);
000682 sqlite3DbFree(dbMem, p);
000683 }
000684 }
000685
000686 /*
000687 ** This function is called to generate code that runs when table pTab is
000688 ** being dropped from the database. The SrcList passed as the second argument
000689 ** to this function contains a single entry guaranteed to resolve to
000690 ** table pTab.
000691 **
000692 ** Normally, no code is required. However, if either
000693 **
000694 ** (a) The table is the parent table of a FK constraint, or
000695 ** (b) The table is the child table of a deferred FK constraint and it is
000696 ** determined at runtime that there are outstanding deferred FK
000697 ** constraint violations in the database,
000698 **
000699 ** then the equivalent of "DELETE FROM <tbl>" is executed before dropping
000700 ** the table from the database. Triggers are disabled while running this
000701 ** DELETE, but foreign key actions are not.
000702 */
000703 void sqlite3FkDropTable(Parse *pParse, SrcList *pName, Table *pTab){
000704 sqlite3 *db = pParse->db;
000705 if( (db->flags&SQLITE_ForeignKeys) && !IsVirtual(pTab) && !pTab->pSelect ){
000706 int iSkip = 0;
000707 Vdbe *v = sqlite3GetVdbe(pParse);
000708
000709 assert( v ); /* VDBE has already been allocated */
000710 if( sqlite3FkReferences(pTab)==0 ){
000711 /* Search for a deferred foreign key constraint for which this table
000712 ** is the child table. If one cannot be found, return without
000713 ** generating any VDBE code. If one can be found, then jump over
000714 ** the entire DELETE if there are no outstanding deferred constraints
000715 ** when this statement is run. */
000716 FKey *p;
000717 for(p=pTab->pFKey; p; p=p->pNextFrom){
000718 if( p->isDeferred || (db->flags & SQLITE_DeferFKs) ) break;
000719 }
000720 if( !p ) return;
000721 iSkip = sqlite3VdbeMakeLabel(v);
000722 sqlite3VdbeAddOp2(v, OP_FkIfZero, 1, iSkip); VdbeCoverage(v);
000723 }
000724
000725 pParse->disableTriggers = 1;
000726 sqlite3DeleteFrom(pParse, sqlite3SrcListDup(db, pName, 0), 0);
000727 pParse->disableTriggers = 0;
000728
000729 /* If the DELETE has generated immediate foreign key constraint
000730 ** violations, halt the VDBE and return an error at this point, before
000731 ** any modifications to the schema are made. This is because statement
000732 ** transactions are not able to rollback schema changes.
000733 **
000734 ** If the SQLITE_DeferFKs flag is set, then this is not required, as
000735 ** the statement transaction will not be rolled back even if FK
000736 ** constraints are violated.
000737 */
000738 if( (db->flags & SQLITE_DeferFKs)==0 ){
000739 sqlite3VdbeAddOp2(v, OP_FkIfZero, 0, sqlite3VdbeCurrentAddr(v)+2);
000740 VdbeCoverage(v);
000741 sqlite3HaltConstraint(pParse, SQLITE_CONSTRAINT_FOREIGNKEY,
000742 OE_Abort, 0, P4_STATIC, P5_ConstraintFK);
000743 }
000744
000745 if( iSkip ){
000746 sqlite3VdbeResolveLabel(v, iSkip);
000747 }
000748 }
000749 }
000750
000751
000752 /*
000753 ** The second argument points to an FKey object representing a foreign key
000754 ** for which pTab is the child table. An UPDATE statement against pTab
000755 ** is currently being processed. For each column of the table that is
000756 ** actually updated, the corresponding element in the aChange[] array
000757 ** is zero or greater (if a column is unmodified the corresponding element
000758 ** is set to -1). If the rowid column is modified by the UPDATE statement
000759 ** the bChngRowid argument is non-zero.
000760 **
000761 ** This function returns true if any of the columns that are part of the
000762 ** child key for FK constraint *p are modified.
000763 */
000764 static int fkChildIsModified(
000765 Table *pTab, /* Table being updated */
000766 FKey *p, /* Foreign key for which pTab is the child */
000767 int *aChange, /* Array indicating modified columns */
000768 int bChngRowid /* True if rowid is modified by this update */
000769 ){
000770 int i;
000771 for(i=0; i<p->nCol; i++){
000772 int iChildKey = p->aCol[i].iFrom;
000773 if( aChange[iChildKey]>=0 ) return 1;
000774 if( iChildKey==pTab->iPKey && bChngRowid ) return 1;
000775 }
000776 return 0;
000777 }
000778
000779 /*
000780 ** The second argument points to an FKey object representing a foreign key
000781 ** for which pTab is the parent table. An UPDATE statement against pTab
000782 ** is currently being processed. For each column of the table that is
000783 ** actually updated, the corresponding element in the aChange[] array
000784 ** is zero or greater (if a column is unmodified the corresponding element
000785 ** is set to -1). If the rowid column is modified by the UPDATE statement
000786 ** the bChngRowid argument is non-zero.
000787 **
000788 ** This function returns true if any of the columns that are part of the
000789 ** parent key for FK constraint *p are modified.
000790 */
000791 static int fkParentIsModified(
000792 Table *pTab,
000793 FKey *p,
000794 int *aChange,
000795 int bChngRowid
000796 ){
000797 int i;
000798 for(i=0; i<p->nCol; i++){
000799 char *zKey = p->aCol[i].zCol;
000800 int iKey;
000801 for(iKey=0; iKey<pTab->nCol; iKey++){
000802 if( aChange[iKey]>=0 || (iKey==pTab->iPKey && bChngRowid) ){
000803 Column *pCol = &pTab->aCol[iKey];
000804 if( zKey ){
000805 if( 0==sqlite3StrICmp(pCol->zName, zKey) ) return 1;
000806 }else if( pCol->colFlags & COLFLAG_PRIMKEY ){
000807 return 1;
000808 }
000809 }
000810 }
000811 }
000812 return 0;
000813 }
000814
000815 /*
000816 ** Return true if the parser passed as the first argument is being
000817 ** used to code a trigger that is really a "SET NULL" action belonging
000818 ** to trigger pFKey.
000819 */
000820 static int isSetNullAction(Parse *pParse, FKey *pFKey){
000821 Parse *pTop = sqlite3ParseToplevel(pParse);
000822 if( pTop->pTriggerPrg ){
000823 Trigger *p = pTop->pTriggerPrg->pTrigger;
000824 if( (p==pFKey->apTrigger[0] && pFKey->aAction[0]==OE_SetNull)
000825 || (p==pFKey->apTrigger[1] && pFKey->aAction[1]==OE_SetNull)
000826 ){
000827 return 1;
000828 }
000829 }
000830 return 0;
000831 }
000832
000833 /*
000834 ** This function is called when inserting, deleting or updating a row of
000835 ** table pTab to generate VDBE code to perform foreign key constraint
000836 ** processing for the operation.
000837 **
000838 ** For a DELETE operation, parameter regOld is passed the index of the
000839 ** first register in an array of (pTab->nCol+1) registers containing the
000840 ** rowid of the row being deleted, followed by each of the column values
000841 ** of the row being deleted, from left to right. Parameter regNew is passed
000842 ** zero in this case.
000843 **
000844 ** For an INSERT operation, regOld is passed zero and regNew is passed the
000845 ** first register of an array of (pTab->nCol+1) registers containing the new
000846 ** row data.
000847 **
000848 ** For an UPDATE operation, this function is called twice. Once before
000849 ** the original record is deleted from the table using the calling convention
000850 ** described for DELETE. Then again after the original record is deleted
000851 ** but before the new record is inserted using the INSERT convention.
000852 */
000853 void sqlite3FkCheck(
000854 Parse *pParse, /* Parse context */
000855 Table *pTab, /* Row is being deleted from this table */
000856 int regOld, /* Previous row data is stored here */
000857 int regNew, /* New row data is stored here */
000858 int *aChange, /* Array indicating UPDATEd columns (or 0) */
000859 int bChngRowid /* True if rowid is UPDATEd */
000860 ){
000861 sqlite3 *db = pParse->db; /* Database handle */
000862 FKey *pFKey; /* Used to iterate through FKs */
000863 int iDb; /* Index of database containing pTab */
000864 const char *zDb; /* Name of database containing pTab */
000865 int isIgnoreErrors = pParse->disableTriggers;
000866
000867 /* Exactly one of regOld and regNew should be non-zero. */
000868 assert( (regOld==0)!=(regNew==0) );
000869
000870 /* If foreign-keys are disabled, this function is a no-op. */
000871 if( (db->flags&SQLITE_ForeignKeys)==0 ) return;
000872
000873 iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
000874 zDb = db->aDb[iDb].zDbSName;
000875
000876 /* Loop through all the foreign key constraints for which pTab is the
000877 ** child table (the table that the foreign key definition is part of). */
000878 for(pFKey=pTab->pFKey; pFKey; pFKey=pFKey->pNextFrom){
000879 Table *pTo; /* Parent table of foreign key pFKey */
000880 Index *pIdx = 0; /* Index on key columns in pTo */
000881 int *aiFree = 0;
000882 int *aiCol;
000883 int iCol;
000884 int i;
000885 int bIgnore = 0;
000886
000887 if( aChange
000888 && sqlite3_stricmp(pTab->zName, pFKey->zTo)!=0
000889 && fkChildIsModified(pTab, pFKey, aChange, bChngRowid)==0
000890 ){
000891 continue;
000892 }
000893
000894 /* Find the parent table of this foreign key. Also find a unique index
000895 ** on the parent key columns in the parent table. If either of these
000896 ** schema items cannot be located, set an error in pParse and return
000897 ** early. */
000898 if( pParse->disableTriggers ){
000899 pTo = sqlite3FindTable(db, pFKey->zTo, zDb);
000900 }else{
000901 pTo = sqlite3LocateTable(pParse, 0, pFKey->zTo, zDb);
000902 }
000903 if( !pTo || sqlite3FkLocateIndex(pParse, pTo, pFKey, &pIdx, &aiFree) ){
000904 assert( isIgnoreErrors==0 || (regOld!=0 && regNew==0) );
000905 if( !isIgnoreErrors || db->mallocFailed ) return;
000906 if( pTo==0 ){
000907 /* If isIgnoreErrors is true, then a table is being dropped. In this
000908 ** case SQLite runs a "DELETE FROM xxx" on the table being dropped
000909 ** before actually dropping it in order to check FK constraints.
000910 ** If the parent table of an FK constraint on the current table is
000911 ** missing, behave as if it is empty. i.e. decrement the relevant
000912 ** FK counter for each row of the current table with non-NULL keys.
000913 */
000914 Vdbe *v = sqlite3GetVdbe(pParse);
000915 int iJump = sqlite3VdbeCurrentAddr(v) + pFKey->nCol + 1;
000916 for(i=0; i<pFKey->nCol; i++){
000917 int iReg = pFKey->aCol[i].iFrom + regOld + 1;
000918 sqlite3VdbeAddOp2(v, OP_IsNull, iReg, iJump); VdbeCoverage(v);
000919 }
000920 sqlite3VdbeAddOp2(v, OP_FkCounter, pFKey->isDeferred, -1);
000921 }
000922 continue;
000923 }
000924 assert( pFKey->nCol==1 || (aiFree && pIdx) );
000925
000926 if( aiFree ){
000927 aiCol = aiFree;
000928 }else{
000929 iCol = pFKey->aCol[0].iFrom;
000930 aiCol = &iCol;
000931 }
000932 for(i=0; i<pFKey->nCol; i++){
000933 if( aiCol[i]==pTab->iPKey ){
000934 aiCol[i] = -1;
000935 }
000936 assert( pIdx==0 || pIdx->aiColumn[i]>=0 );
000937 #ifndef SQLITE_OMIT_AUTHORIZATION
000938 /* Request permission to read the parent key columns. If the
000939 ** authorization callback returns SQLITE_IGNORE, behave as if any
000940 ** values read from the parent table are NULL. */
000941 if( db->xAuth ){
000942 int rcauth;
000943 char *zCol = pTo->aCol[pIdx ? pIdx->aiColumn[i] : pTo->iPKey].zName;
000944 rcauth = sqlite3AuthReadCol(pParse, pTo->zName, zCol, iDb);
000945 bIgnore = (rcauth==SQLITE_IGNORE);
000946 }
000947 #endif
000948 }
000949
000950 /* Take a shared-cache advisory read-lock on the parent table. Allocate
000951 ** a cursor to use to search the unique index on the parent key columns
000952 ** in the parent table. */
000953 sqlite3TableLock(pParse, iDb, pTo->tnum, 0, pTo->zName);
000954 pParse->nTab++;
000955
000956 if( regOld!=0 ){
000957 /* A row is being removed from the child table. Search for the parent.
000958 ** If the parent does not exist, removing the child row resolves an
000959 ** outstanding foreign key constraint violation. */
000960 fkLookupParent(pParse, iDb, pTo, pIdx, pFKey, aiCol, regOld, -1, bIgnore);
000961 }
000962 if( regNew!=0 && !isSetNullAction(pParse, pFKey) ){
000963 /* A row is being added to the child table. If a parent row cannot
000964 ** be found, adding the child row has violated the FK constraint.
000965 **
000966 ** If this operation is being performed as part of a trigger program
000967 ** that is actually a "SET NULL" action belonging to this very
000968 ** foreign key, then omit this scan altogether. As all child key
000969 ** values are guaranteed to be NULL, it is not possible for adding
000970 ** this row to cause an FK violation. */
000971 fkLookupParent(pParse, iDb, pTo, pIdx, pFKey, aiCol, regNew, +1, bIgnore);
000972 }
000973
000974 sqlite3DbFree(db, aiFree);
000975 }
000976
000977 /* Loop through all the foreign key constraints that refer to this table.
000978 ** (the "child" constraints) */
000979 for(pFKey = sqlite3FkReferences(pTab); pFKey; pFKey=pFKey->pNextTo){
000980 Index *pIdx = 0; /* Foreign key index for pFKey */
000981 SrcList *pSrc;
000982 int *aiCol = 0;
000983
000984 if( aChange && fkParentIsModified(pTab, pFKey, aChange, bChngRowid)==0 ){
000985 continue;
000986 }
000987
000988 if( !pFKey->isDeferred && !(db->flags & SQLITE_DeferFKs)
000989 && !pParse->pToplevel && !pParse->isMultiWrite
000990 ){
000991 assert( regOld==0 && regNew!=0 );
000992 /* Inserting a single row into a parent table cannot cause (or fix)
000993 ** an immediate foreign key violation. So do nothing in this case. */
000994 continue;
000995 }
000996
000997 if( sqlite3FkLocateIndex(pParse, pTab, pFKey, &pIdx, &aiCol) ){
000998 if( !isIgnoreErrors || db->mallocFailed ) return;
000999 continue;
001000 }
001001 assert( aiCol || pFKey->nCol==1 );
001002
001003 /* Create a SrcList structure containing the child table. We need the
001004 ** child table as a SrcList for sqlite3WhereBegin() */
001005 pSrc = sqlite3SrcListAppend(db, 0, 0, 0);
001006 if( pSrc ){
001007 struct SrcList_item *pItem = pSrc->a;
001008 pItem->pTab = pFKey->pFrom;
001009 pItem->zName = pFKey->pFrom->zName;
001010 pItem->pTab->nTabRef++;
001011 pItem->iCursor = pParse->nTab++;
001012
001013 if( regNew!=0 ){
001014 fkScanChildren(pParse, pSrc, pTab, pIdx, pFKey, aiCol, regNew, -1);
001015 }
001016 if( regOld!=0 ){
001017 int eAction = pFKey->aAction[aChange!=0];
001018 fkScanChildren(pParse, pSrc, pTab, pIdx, pFKey, aiCol, regOld, 1);
001019 /* If this is a deferred FK constraint, or a CASCADE or SET NULL
001020 ** action applies, then any foreign key violations caused by
001021 ** removing the parent key will be rectified by the action trigger.
001022 ** So do not set the "may-abort" flag in this case.
001023 **
001024 ** Note 1: If the FK is declared "ON UPDATE CASCADE", then the
001025 ** may-abort flag will eventually be set on this statement anyway
001026 ** (when this function is called as part of processing the UPDATE
001027 ** within the action trigger).
001028 **
001029 ** Note 2: At first glance it may seem like SQLite could simply omit
001030 ** all OP_FkCounter related scans when either CASCADE or SET NULL
001031 ** applies. The trouble starts if the CASCADE or SET NULL action
001032 ** trigger causes other triggers or action rules attached to the
001033 ** child table to fire. In these cases the fk constraint counters
001034 ** might be set incorrectly if any OP_FkCounter related scans are
001035 ** omitted. */
001036 if( !pFKey->isDeferred && eAction!=OE_Cascade && eAction!=OE_SetNull ){
001037 sqlite3MayAbort(pParse);
001038 }
001039 }
001040 pItem->zName = 0;
001041 sqlite3SrcListDelete(db, pSrc);
001042 }
001043 sqlite3DbFree(db, aiCol);
001044 }
001045 }
001046
001047 #define COLUMN_MASK(x) (((x)>31) ? 0xffffffff : ((u32)1<<(x)))
001048
001049 /*
001050 ** This function is called before generating code to update or delete a
001051 ** row contained in table pTab.
001052 */
001053 u32 sqlite3FkOldmask(
001054 Parse *pParse, /* Parse context */
001055 Table *pTab /* Table being modified */
001056 ){
001057 u32 mask = 0;
001058 if( pParse->db->flags&SQLITE_ForeignKeys ){
001059 FKey *p;
001060 int i;
001061 for(p=pTab->pFKey; p; p=p->pNextFrom){
001062 for(i=0; i<p->nCol; i++) mask |= COLUMN_MASK(p->aCol[i].iFrom);
001063 }
001064 for(p=sqlite3FkReferences(pTab); p; p=p->pNextTo){
001065 Index *pIdx = 0;
001066 sqlite3FkLocateIndex(pParse, pTab, p, &pIdx, 0);
001067 if( pIdx ){
001068 for(i=0; i<pIdx->nKeyCol; i++){
001069 assert( pIdx->aiColumn[i]>=0 );
001070 mask |= COLUMN_MASK(pIdx->aiColumn[i]);
001071 }
001072 }
001073 }
001074 }
001075 return mask;
001076 }
001077
001078
001079 /*
001080 ** This function is called before generating code to update or delete a
001081 ** row contained in table pTab. If the operation is a DELETE, then
001082 ** parameter aChange is passed a NULL value. For an UPDATE, aChange points
001083 ** to an array of size N, where N is the number of columns in table pTab.
001084 ** If the i'th column is not modified by the UPDATE, then the corresponding
001085 ** entry in the aChange[] array is set to -1. If the column is modified,
001086 ** the value is 0 or greater. Parameter chngRowid is set to true if the
001087 ** UPDATE statement modifies the rowid fields of the table.
001088 **
001089 ** If any foreign key processing will be required, this function returns
001090 ** true. If there is no foreign key related processing, this function
001091 ** returns false.
001092 */
001093 int sqlite3FkRequired(
001094 Parse *pParse, /* Parse context */
001095 Table *pTab, /* Table being modified */
001096 int *aChange, /* Non-NULL for UPDATE operations */
001097 int chngRowid /* True for UPDATE that affects rowid */
001098 ){
001099 if( pParse->db->flags&SQLITE_ForeignKeys ){
001100 if( !aChange ){
001101 /* A DELETE operation. Foreign key processing is required if the
001102 ** table in question is either the child or parent table for any
001103 ** foreign key constraint. */
001104 return (sqlite3FkReferences(pTab) || pTab->pFKey);
001105 }else{
001106 /* This is an UPDATE. Foreign key processing is only required if the
001107 ** operation modifies one or more child or parent key columns. */
001108 FKey *p;
001109
001110 /* Check if any child key columns are being modified. */
001111 for(p=pTab->pFKey; p; p=p->pNextFrom){
001112 if( fkChildIsModified(pTab, p, aChange, chngRowid) ) return 1;
001113 }
001114
001115 /* Check if any parent key columns are being modified. */
001116 for(p=sqlite3FkReferences(pTab); p; p=p->pNextTo){
001117 if( fkParentIsModified(pTab, p, aChange, chngRowid) ) return 1;
001118 }
001119 }
001120 }
001121 return 0;
001122 }
001123
001124 /*
001125 ** This function is called when an UPDATE or DELETE operation is being
001126 ** compiled on table pTab, which is the parent table of foreign-key pFKey.
001127 ** If the current operation is an UPDATE, then the pChanges parameter is
001128 ** passed a pointer to the list of columns being modified. If it is a
001129 ** DELETE, pChanges is passed a NULL pointer.
001130 **
001131 ** It returns a pointer to a Trigger structure containing a trigger
001132 ** equivalent to the ON UPDATE or ON DELETE action specified by pFKey.
001133 ** If the action is "NO ACTION" or "RESTRICT", then a NULL pointer is
001134 ** returned (these actions require no special handling by the triggers
001135 ** sub-system, code for them is created by fkScanChildren()).
001136 **
001137 ** For example, if pFKey is the foreign key and pTab is table "p" in
001138 ** the following schema:
001139 **
001140 ** CREATE TABLE p(pk PRIMARY KEY);
001141 ** CREATE TABLE c(ck REFERENCES p ON DELETE CASCADE);
001142 **
001143 ** then the returned trigger structure is equivalent to:
001144 **
001145 ** CREATE TRIGGER ... DELETE ON p BEGIN
001146 ** DELETE FROM c WHERE ck = old.pk;
001147 ** END;
001148 **
001149 ** The returned pointer is cached as part of the foreign key object. It
001150 ** is eventually freed along with the rest of the foreign key object by
001151 ** sqlite3FkDelete().
001152 */
001153 static Trigger *fkActionTrigger(
001154 Parse *pParse, /* Parse context */
001155 Table *pTab, /* Table being updated or deleted from */
001156 FKey *pFKey, /* Foreign key to get action for */
001157 ExprList *pChanges /* Change-list for UPDATE, NULL for DELETE */
001158 ){
001159 sqlite3 *db = pParse->db; /* Database handle */
001160 int action; /* One of OE_None, OE_Cascade etc. */
001161 Trigger *pTrigger; /* Trigger definition to return */
001162 int iAction = (pChanges!=0); /* 1 for UPDATE, 0 for DELETE */
001163
001164 action = pFKey->aAction[iAction];
001165 if( action==OE_Restrict && (db->flags & SQLITE_DeferFKs) ){
001166 return 0;
001167 }
001168 pTrigger = pFKey->apTrigger[iAction];
001169
001170 if( action!=OE_None && !pTrigger ){
001171 char const *zFrom; /* Name of child table */
001172 int nFrom; /* Length in bytes of zFrom */
001173 Index *pIdx = 0; /* Parent key index for this FK */
001174 int *aiCol = 0; /* child table cols -> parent key cols */
001175 TriggerStep *pStep = 0; /* First (only) step of trigger program */
001176 Expr *pWhere = 0; /* WHERE clause of trigger step */
001177 ExprList *pList = 0; /* Changes list if ON UPDATE CASCADE */
001178 Select *pSelect = 0; /* If RESTRICT, "SELECT RAISE(...)" */
001179 int i; /* Iterator variable */
001180 Expr *pWhen = 0; /* WHEN clause for the trigger */
001181
001182 if( sqlite3FkLocateIndex(pParse, pTab, pFKey, &pIdx, &aiCol) ) return 0;
001183 assert( aiCol || pFKey->nCol==1 );
001184
001185 for(i=0; i<pFKey->nCol; i++){
001186 Token tOld = { "old", 3 }; /* Literal "old" token */
001187 Token tNew = { "new", 3 }; /* Literal "new" token */
001188 Token tFromCol; /* Name of column in child table */
001189 Token tToCol; /* Name of column in parent table */
001190 int iFromCol; /* Idx of column in child table */
001191 Expr *pEq; /* tFromCol = OLD.tToCol */
001192
001193 iFromCol = aiCol ? aiCol[i] : pFKey->aCol[0].iFrom;
001194 assert( iFromCol>=0 );
001195 assert( pIdx!=0 || (pTab->iPKey>=0 && pTab->iPKey<pTab->nCol) );
001196 assert( pIdx==0 || pIdx->aiColumn[i]>=0 );
001197 sqlite3TokenInit(&tToCol,
001198 pTab->aCol[pIdx ? pIdx->aiColumn[i] : pTab->iPKey].zName);
001199 sqlite3TokenInit(&tFromCol, pFKey->pFrom->aCol[iFromCol].zName);
001200
001201 /* Create the expression "OLD.zToCol = zFromCol". It is important
001202 ** that the "OLD.zToCol" term is on the LHS of the = operator, so
001203 ** that the affinity and collation sequence associated with the
001204 ** parent table are used for the comparison. */
001205 pEq = sqlite3PExpr(pParse, TK_EQ,
001206 sqlite3PExpr(pParse, TK_DOT,
001207 sqlite3ExprAlloc(db, TK_ID, &tOld, 0),
001208 sqlite3ExprAlloc(db, TK_ID, &tToCol, 0)),
001209 sqlite3ExprAlloc(db, TK_ID, &tFromCol, 0)
001210 );
001211 pWhere = sqlite3ExprAnd(db, pWhere, pEq);
001212
001213 /* For ON UPDATE, construct the next term of the WHEN clause.
001214 ** The final WHEN clause will be like this:
001215 **
001216 ** WHEN NOT(old.col1 IS new.col1 AND ... AND old.colN IS new.colN)
001217 */
001218 if( pChanges ){
001219 pEq = sqlite3PExpr(pParse, TK_IS,
001220 sqlite3PExpr(pParse, TK_DOT,
001221 sqlite3ExprAlloc(db, TK_ID, &tOld, 0),
001222 sqlite3ExprAlloc(db, TK_ID, &tToCol, 0)),
001223 sqlite3PExpr(pParse, TK_DOT,
001224 sqlite3ExprAlloc(db, TK_ID, &tNew, 0),
001225 sqlite3ExprAlloc(db, TK_ID, &tToCol, 0))
001226 );
001227 pWhen = sqlite3ExprAnd(db, pWhen, pEq);
001228 }
001229
001230 if( action!=OE_Restrict && (action!=OE_Cascade || pChanges) ){
001231 Expr *pNew;
001232 if( action==OE_Cascade ){
001233 pNew = sqlite3PExpr(pParse, TK_DOT,
001234 sqlite3ExprAlloc(db, TK_ID, &tNew, 0),
001235 sqlite3ExprAlloc(db, TK_ID, &tToCol, 0));
001236 }else if( action==OE_SetDflt ){
001237 Expr *pDflt = pFKey->pFrom->aCol[iFromCol].pDflt;
001238 if( pDflt ){
001239 pNew = sqlite3ExprDup(db, pDflt, 0);
001240 }else{
001241 pNew = sqlite3ExprAlloc(db, TK_NULL, 0, 0);
001242 }
001243 }else{
001244 pNew = sqlite3ExprAlloc(db, TK_NULL, 0, 0);
001245 }
001246 pList = sqlite3ExprListAppend(pParse, pList, pNew);
001247 sqlite3ExprListSetName(pParse, pList, &tFromCol, 0);
001248 }
001249 }
001250 sqlite3DbFree(db, aiCol);
001251
001252 zFrom = pFKey->pFrom->zName;
001253 nFrom = sqlite3Strlen30(zFrom);
001254
001255 if( action==OE_Restrict ){
001256 Token tFrom;
001257 Expr *pRaise;
001258
001259 tFrom.z = zFrom;
001260 tFrom.n = nFrom;
001261 pRaise = sqlite3Expr(db, TK_RAISE, "FOREIGN KEY constraint failed");
001262 if( pRaise ){
001263 pRaise->affinity = OE_Abort;
001264 }
001265 pSelect = sqlite3SelectNew(pParse,
001266 sqlite3ExprListAppend(pParse, 0, pRaise),
001267 sqlite3SrcListAppend(db, 0, &tFrom, 0),
001268 pWhere,
001269 0, 0, 0, 0, 0, 0
001270 );
001271 pWhere = 0;
001272 }
001273
001274 /* Disable lookaside memory allocation */
001275 db->lookaside.bDisable++;
001276
001277 pTrigger = (Trigger *)sqlite3DbMallocZero(db,
001278 sizeof(Trigger) + /* struct Trigger */
001279 sizeof(TriggerStep) + /* Single step in trigger program */
001280 nFrom + 1 /* Space for pStep->zTarget */
001281 );
001282 if( pTrigger ){
001283 pStep = pTrigger->step_list = (TriggerStep *)&pTrigger[1];
001284 pStep->zTarget = (char *)&pStep[1];
001285 memcpy((char *)pStep->zTarget, zFrom, nFrom);
001286
001287 pStep->pWhere = sqlite3ExprDup(db, pWhere, EXPRDUP_REDUCE);
001288 pStep->pExprList = sqlite3ExprListDup(db, pList, EXPRDUP_REDUCE);
001289 pStep->pSelect = sqlite3SelectDup(db, pSelect, EXPRDUP_REDUCE);
001290 if( pWhen ){
001291 pWhen = sqlite3PExpr(pParse, TK_NOT, pWhen, 0);
001292 pTrigger->pWhen = sqlite3ExprDup(db, pWhen, EXPRDUP_REDUCE);
001293 }
001294 }
001295
001296 /* Re-enable the lookaside buffer, if it was disabled earlier. */
001297 db->lookaside.bDisable--;
001298
001299 sqlite3ExprDelete(db, pWhere);
001300 sqlite3ExprDelete(db, pWhen);
001301 sqlite3ExprListDelete(db, pList);
001302 sqlite3SelectDelete(db, pSelect);
001303 if( db->mallocFailed==1 ){
001304 fkTriggerDelete(db, pTrigger);
001305 return 0;
001306 }
001307 assert( pStep!=0 );
001308
001309 switch( action ){
001310 case OE_Restrict:
001311 pStep->op = TK_SELECT;
001312 break;
001313 case OE_Cascade:
001314 if( !pChanges ){
001315 pStep->op = TK_DELETE;
001316 break;
001317 }
001318 default:
001319 pStep->op = TK_UPDATE;
001320 }
001321 pStep->pTrig = pTrigger;
001322 pTrigger->pSchema = pTab->pSchema;
001323 pTrigger->pTabSchema = pTab->pSchema;
001324 pFKey->apTrigger[iAction] = pTrigger;
001325 pTrigger->op = (pChanges ? TK_UPDATE : TK_DELETE);
001326 }
001327
001328 return pTrigger;
001329 }
001330
001331 /*
001332 ** This function is called when deleting or updating a row to implement
001333 ** any required CASCADE, SET NULL or SET DEFAULT actions.
001334 */
001335 void sqlite3FkActions(
001336 Parse *pParse, /* Parse context */
001337 Table *pTab, /* Table being updated or deleted from */
001338 ExprList *pChanges, /* Change-list for UPDATE, NULL for DELETE */
001339 int regOld, /* Address of array containing old row */
001340 int *aChange, /* Array indicating UPDATEd columns (or 0) */
001341 int bChngRowid /* True if rowid is UPDATEd */
001342 ){
001343 /* If foreign-key support is enabled, iterate through all FKs that
001344 ** refer to table pTab. If there is an action associated with the FK
001345 ** for this operation (either update or delete), invoke the associated
001346 ** trigger sub-program. */
001347 if( pParse->db->flags&SQLITE_ForeignKeys ){
001348 FKey *pFKey; /* Iterator variable */
001349 for(pFKey = sqlite3FkReferences(pTab); pFKey; pFKey=pFKey->pNextTo){
001350 if( aChange==0 || fkParentIsModified(pTab, pFKey, aChange, bChngRowid) ){
001351 Trigger *pAct = fkActionTrigger(pParse, pTab, pFKey, pChanges);
001352 if( pAct ){
001353 sqlite3CodeRowTriggerDirect(pParse, pAct, pTab, regOld, OE_Abort, 0);
001354 }
001355 }
001356 }
001357 }
001358 }
001359
001360 #endif /* ifndef SQLITE_OMIT_TRIGGER */
001361
001362 /*
001363 ** Free all memory associated with foreign key definitions attached to
001364 ** table pTab. Remove the deleted foreign keys from the Schema.fkeyHash
001365 ** hash table.
001366 */
001367 void sqlite3FkDelete(sqlite3 *db, Table *pTab){
001368 FKey *pFKey; /* Iterator variable */
001369 FKey *pNext; /* Copy of pFKey->pNextFrom */
001370
001371 assert( db==0 || IsVirtual(pTab)
001372 || sqlite3SchemaMutexHeld(db, 0, pTab->pSchema) );
001373 for(pFKey=pTab->pFKey; pFKey; pFKey=pNext){
001374
001375 /* Remove the FK from the fkeyHash hash table. */
001376 if( !db || db->pnBytesFreed==0 ){
001377 if( pFKey->pPrevTo ){
001378 pFKey->pPrevTo->pNextTo = pFKey->pNextTo;
001379 }else{
001380 void *p = (void *)pFKey->pNextTo;
001381 const char *z = (p ? pFKey->pNextTo->zTo : pFKey->zTo);
001382 sqlite3HashInsert(&pTab->pSchema->fkeyHash, z, p);
001383 }
001384 if( pFKey->pNextTo ){
001385 pFKey->pNextTo->pPrevTo = pFKey->pPrevTo;
001386 }
001387 }
001388
001389 /* EV: R-30323-21917 Each foreign key constraint in SQLite is
001390 ** classified as either immediate or deferred.
001391 */
001392 assert( pFKey->isDeferred==0 || pFKey->isDeferred==1 );
001393
001394 /* Delete any triggers created to implement actions for this FK. */
001395 #ifndef SQLITE_OMIT_TRIGGER
001396 fkTriggerDelete(db, pFKey->apTrigger[0]);
001397 fkTriggerDelete(db, pFKey->apTrigger[1]);
001398 #endif
001399
001400 pNext = pFKey->pNextFrom;
001401 sqlite3DbFree(db, pFKey);
001402 }
001403 }
001404 #endif /* ifndef SQLITE_OMIT_FOREIGN_KEY */