/* ** ** The author disclaims copyright to this source code. In place of ** a legal notice, here is a blessing: ** ** May you do good and not evil. ** May you find forgiveness for yourself and forgive others. ** May you share freely, never taking more than you give. ** ************************************************************************* ** This file contains code used by the compiler to add foreign key ** support to compiled SQL statements. */ #include "sqliteInt.h" #ifndef SQLITE_OMIT_FOREIGN_KEY #ifndef SQLITE_OMIT_TRIGGER /* ** Deferred and Immediate FKs ** -------------------------- ** ** Foreign keys in SQLite come in two flavours: deferred and immediate. ** If an immediate foreign key constraint is violated, SQLITE_CONSTRAINT ** is returned and the current statement transaction rolled back. If a ** deferred foreign key constraint is violated, no action is taken ** immediately. However if the application attempts to commit the ** transaction before fixing the constraint violation, the attempt fails. ** ** Deferred constraints are implemented using a simple counter associated ** with the database handle. The counter is set to zero each time a ** database transaction is opened. Each time a statement is executed ** that causes a foreign key violation, the counter is incremented. Each ** time a statement is executed that removes an existing violation from ** the database, the counter is decremented. When the transaction is ** committed, the commit fails if the current value of the counter is ** greater than zero. This scheme has two big drawbacks: ** ** * When a commit fails due to a deferred foreign key constraint, ** there is no way to tell which foreign constraint is not satisfied, ** or which row it is not satisfied for. ** ** * If the database contains foreign key violations when the ** transaction is opened, this may cause the mechanism to malfunction. ** ** Despite these problems, this approach is adopted as it seems simpler ** than the alternatives. ** ** INSERT operations: ** ** I.1) For each FK for which the table is the child table, search ** the parent table for a match. If none is found increment the ** constraint counter. ** ** I.2) For each FK for which the table is the parent table, ** search the child table for rows that correspond to the new ** row in the parent table. Decrement the counter for each row ** found (as the constraint is now satisfied). ** ** DELETE operations: ** ** D.1) For each FK for which the table is the child table, ** search the parent table for a row that corresponds to the ** deleted row in the child table. If such a row is not found, ** decrement the counter. ** ** D.2) For each FK for which the table is the parent table, search ** the child table for rows that correspond to the deleted row ** in the parent table. For each found increment the counter. ** ** UPDATE operations: ** ** An UPDATE command requires that all 4 steps above are taken, but only ** for FK constraints for which the affected columns are actually ** modified (values must be compared at runtime). ** ** Note that I.1 and D.1 are very similar operations, as are I.2 and D.2. ** This simplifies the implementation a bit. ** ** For the purposes of immediate FK constraints, the OR REPLACE conflict ** resolution is considered to delete rows before the new row is inserted. ** If a delete caused by OR REPLACE violates an FK constraint, an exception ** is thrown, even if the FK constraint would be satisfied after the new ** row is inserted. ** ** Immediate constraints are usually handled similarly. The only difference ** is that the counter used is stored as part of each individual statement ** object (struct Vdbe). If, after the statement has run, its immediate ** constraint counter is greater than zero, it returns SQLITE_CONSTRAINT ** and the statement transaction is rolled back. An exception is an INSERT ** statement that inserts a single row only (no triggers). In this case, ** instead of using a counter, an exception is thrown immediately if the ** INSERT violates a foreign key constraint. This is necessary as such ** an INSERT does not open a statement transaction. ** ** TODO: How should dropping a table be handled? How should renaming a ** table be handled? ** ** ** Query API Notes ** --------------- ** ** Before coding an UPDATE or DELETE row operation, the code-generator ** for those two operations needs to know whether or not the operation ** requires any FK processing and, if so, which columns of the original ** row are required by the FK processing VDBE code (i.e. if FKs were ** implemented using triggers, which of the old.* columns would be ** accessed). No information is required by the code-generator before ** coding an INSERT operation. The functions used by the UPDATE/DELETE ** generation code to query for this information are: ** ** sqlite3FkRequired() - Test to see if FK processing is required. ** sqlite3FkOldmask() - Query for the set of required old.* columns. ** ** ** Externally accessible module functions ** -------------------------------------- ** ** sqlite3FkCheck() - Check for foreign key violations. ** sqlite3FkActions() - Code triggers for ON UPDATE/ON DELETE actions. ** sqlite3FkDelete() - Delete an FKey structure. */ /* ** VDBE Calling Convention ** ----------------------- ** ** Example: ** ** For the following INSERT statement: ** ** CREATE TABLE t1(a, b INTEGER PRIMARY KEY, c); ** INSERT INTO t1 VALUES(1, 2, 3.1); ** ** Register (x): 2 (type integer) ** Register (x+1): 1 (type integer) ** Register (x+2): NULL (type NULL) ** Register (x+3): 3.1 (type real) */ /* ** A foreign key constraint requires that the key columns in the parent ** table are collectively subject to a UNIQUE or PRIMARY KEY constraint. ** Given that pParent is the parent table for foreign key constraint pFKey, ** search the schema a unique index on the parent key columns. ** ** If successful, zero is returned. If the parent key is an INTEGER PRIMARY ** KEY column, then output variable *ppIdx is set to NULL. Otherwise, *ppIdx ** is set to point to the unique index. ** ** If the parent key consists of a single column (the foreign key constraint ** is not a composite foreign key), output variable *paiCol is set to NULL. ** Otherwise, it is set to point to an allocated array of size N, where ** N is the number of columns in the parent key. The first element of the ** array is the index of the child table column that is mapped by the FK ** constraint to the parent table column stored in the left-most column ** of index *ppIdx. The second element of the array is the index of the ** child table column that corresponds to the second left-most column of ** *ppIdx, and so on. ** ** If the required index cannot be found, either because: ** ** 1) The named parent key columns do not exist, or ** ** 2) The named parent key columns do exist, but are not subject to a ** UNIQUE or PRIMARY KEY constraint, or ** ** 3) No parent key columns were provided explicitly as part of the ** foreign key definition, and the parent table does not have a ** PRIMARY KEY, or ** ** 4) No parent key columns were provided explicitly as part of the ** foreign key definition, and the PRIMARY KEY of the parent table ** consists of a a different number of columns to the child key in ** the child table. ** ** then non-zero is returned, and a "foreign key mismatch" error loaded ** into pParse. If an OOM error occurs, non-zero is returned and the ** pParse->db->mallocFailed flag is set. */ static int locateFkeyIndex( Parse *pParse, /* Parse context to store any error in */ Table *pParent, /* Parent table of FK constraint pFKey */ FKey *pFKey, /* Foreign key to find index for */ Index **ppIdx, /* OUT: Unique index on parent table */ int **paiCol /* OUT: Map of index columns in pFKey */ ){ Index *pIdx = 0; /* Value to return via *ppIdx */ int *aiCol = 0; /* Value to return via *paiCol */ int nCol = pFKey->nCol; /* Number of columns in parent key */ char *zKey = pFKey->aCol[0].zCol; /* Name of left-most parent key column */ /* The caller is responsible for zeroing output parameters. */ assert( ppIdx && *ppIdx==0 ); assert( !paiCol || *paiCol==0 ); assert( pParse ); /* If this is a non-composite (single column) foreign key, check if it ** maps to the INTEGER PRIMARY KEY of table pParent. If so, leave *ppIdx ** and *paiCol set to zero and return early. ** ** Otherwise, for a composite foreign key (more than one column), allocate ** space for the aiCol array (returned via output parameter *paiCol). ** Non-composite foreign keys do not require the aiCol array. */ if( nCol==1 ){ /* The FK maps to the IPK if any of the following are true: ** ** 1) There is an INTEGER PRIMARY KEY column and the FK is implicitly ** mapped to the primary key of table pParent, or ** 2) The FK is explicitly mapped to a column declared as INTEGER ** PRIMARY KEY. */ if( pParent->iPKey>=0 ){ if( !zKey ) return 0; if( !sqlite3StrICmp(pParent->aCol[pParent->iPKey].zName, zKey) ) return 0; } }else if( paiCol ){ assert( nCol>1 ); aiCol = (int *)sqlite3DbMallocRaw(pParse->db, nCol*sizeof(int)); if( !aiCol ) return 1; *paiCol = aiCol; } for(pIdx=pParent->pIndex; pIdx; pIdx=pIdx->pNext){ if( pIdx->nColumn==nCol && pIdx->onError!=OE_None ){ /* pIdx is a UNIQUE index (or a PRIMARY KEY) and has the right number ** of columns. If each indexed column corresponds to a foreign key ** column of pFKey, then this index is a winner. */ if( zKey==0 ){ /* If zKey is NULL, then this foreign key is implicitly mapped to ** the PRIMARY KEY of table pParent. The PRIMARY KEY index may be ** identified by the test (Index.autoIndex==2). */ if( pIdx->autoIndex==2 ){ if( aiCol ){ int i; for(i=0; iaCol[i].iFrom; } break; } }else{ /* If zKey is non-NULL, then this foreign key was declared to ** map to an explicit list of columns in table pParent. Check if this ** index matches those columns. Also, check that the index uses ** the default collation sequences for each column. */ int i, j; for(i=0; iaiColumn[i]; /* Index of column in parent tbl */ char *zDfltColl; /* Def. collation for column */ char *zIdxCol; /* Name of indexed column */ /* If the index uses a collation sequence that is different from ** the default collation sequence for the column, this index is ** unusable. Bail out early in this case. */ zDfltColl = pParent->aCol[iCol].zColl; if( !zDfltColl ){ zDfltColl = "BINARY"; } if( sqlite3StrICmp(pIdx->azColl[i], zDfltColl) ) break; zIdxCol = pParent->aCol[iCol].zName; for(j=0; jaCol[j].zCol, zIdxCol)==0 ){ if( aiCol ) aiCol[i] = pFKey->aCol[j].iFrom; break; } } if( j==nCol ) break; } if( i==nCol ) break; /* pIdx is usable */ } } } if( !pIdx ){ if( !pParse->disableTriggers ){ sqlite3ErrorMsg(pParse, "foreign key mismatch"); } sqlite3DbFree(pParse->db, aiCol); return 1; } *ppIdx = pIdx; return 0; } /* ** This function is called when a row is inserted into or deleted from the ** child table of foreign key constraint pFKey. If an SQL UPDATE is executed ** on the child table of pFKey, this function is invoked twice for each row ** affected - once to "delete" the old row, and then again to "insert" the ** new row. ** ** Each time it is called, this function generates VDBE code to locate the ** row in the parent table that corresponds to the row being inserted into ** or deleted from the child table. If the parent row can be found, no ** special action is taken. Otherwise, if the parent row can *not* be ** found in the parent table: ** ** Operation | FK type | Action taken ** -------------------------------------------------------------------------- ** INSERT immediate Increment the "immediate constraint counter". ** ** DELETE immediate Decrement the "immediate constraint counter". ** ** INSERT deferred Increment the "deferred constraint counter". ** ** DELETE deferred Decrement the "deferred constraint counter". ** ** These operations are identified in the comment at the top of this file ** (fkey.c) as "I.1" and "D.1". */ static void fkLookupParent( Parse *pParse, /* Parse context */ int iDb, /* Index of database housing pTab */ Table *pTab, /* Parent table of FK pFKey */ Index *pIdx, /* Unique index on parent key columns in pTab */ FKey *pFKey, /* Foreign key constraint */ int *aiCol, /* Map from parent key columns to child table columns */ int regData, /* Address of array containing child table row */ int nIncr /* Increment constraint counter by this */ ){ int i; /* Iterator variable */ Vdbe *v = sqlite3GetVdbe(pParse); /* Vdbe to add code to */ int iCur = pParse->nTab - 1; /* Cursor number to use */ int iOk = sqlite3VdbeMakeLabel(v); /* jump here if parent key found */ /* If nIncr is less than zero, then check at runtime if there are any ** outstanding constraints to resolve. If there are not, there is no need ** to check if deleting this row resolves any outstanding violations. ** ** Check if any of the key columns in the child table row are NULL. If ** any are, then the constraint is considered satisfied. No need to ** search for a matching row in the parent table. */ if( nIncr<0 ){ sqlite3VdbeAddOp2(v, OP_FkIfZero, pFKey->isDeferred, iOk); } for(i=0; inCol; i++){ int iReg = aiCol[i] + regData + 1; sqlite3VdbeAddOp2(v, OP_IsNull, iReg, iOk); } if( pIdx==0 ){ /* If pIdx is NULL, then the parent key is the INTEGER PRIMARY KEY ** column of the parent table (table pTab). */ int iMustBeInt; /* Address of MustBeInt instruction */ int regTemp = sqlite3GetTempReg(pParse); /* Invoke MustBeInt to coerce the child key value to an integer (i.e. ** apply the affinity of the parent key). If this fails, then there ** is no matching parent key. Before using MustBeInt, make a copy of ** the value. Otherwise, the value inserted into the child key column ** will have INTEGER affinity applied to it, which may not be correct. */ sqlite3VdbeAddOp2(v, OP_SCopy, aiCol[0]+1+regData, regTemp); iMustBeInt = sqlite3VdbeAddOp2(v, OP_MustBeInt, regTemp, 0); /* If the parent table is the same as the child table, and we are about ** to increment the constraint-counter (i.e. this is an INSERT operation), ** then check if the row being inserted matches itself. If so, do not ** increment the constraint-counter. */ if( pTab==pFKey->pFrom && nIncr==1 ){ sqlite3VdbeAddOp3(v, OP_Eq, regData, iOk, regTemp); } sqlite3OpenTable(pParse, iCur, iDb, pTab, OP_OpenRead); sqlite3VdbeAddOp3(v, OP_NotExists, iCur, 0, regTemp); sqlite3VdbeAddOp2(v, OP_Goto, 0, iOk); sqlite3VdbeJumpHere(v, sqlite3VdbeCurrentAddr(v)-2); sqlite3VdbeJumpHere(v, iMustBeInt); sqlite3ReleaseTempReg(pParse, regTemp); }else{ int nCol = pFKey->nCol; int regTemp = sqlite3GetTempRange(pParse, nCol); int regRec = sqlite3GetTempReg(pParse); KeyInfo *pKey = sqlite3IndexKeyinfo(pParse, pIdx); sqlite3VdbeAddOp3(v, OP_OpenRead, iCur, pIdx->tnum, iDb); sqlite3VdbeChangeP4(v, -1, (char*)pKey, P4_KEYINFO_HANDOFF); for(i=0; ipFrom && nIncr==1 ){ int iJump = sqlite3VdbeCurrentAddr(v) + nCol + 1; for(i=0; iaiColumn[i]+1+regData; sqlite3VdbeAddOp3(v, OP_Ne, iChild, iJump, iParent); } sqlite3VdbeAddOp2(v, OP_Goto, 0, iOk); } sqlite3VdbeAddOp3(v, OP_MakeRecord, regTemp, nCol, regRec); sqlite3VdbeChangeP4(v, -1, sqlite3IndexAffinityStr(v, pIdx), 0); sqlite3VdbeAddOp3(v, OP_Found, iCur, iOk, regRec); sqlite3ReleaseTempReg(pParse, regRec); sqlite3ReleaseTempRange(pParse, regTemp, nCol); } if( !pFKey->isDeferred && !pParse->pToplevel && !pParse->isMultiWrite ){ /* Special case: If this is an INSERT statement that will insert exactly ** one row into the table, raise a constraint immediately instead of ** incrementing a counter. This is necessary as the VM code is being ** generated for will not open a statement transaction. */ assert( nIncr==1 ); sqlite3HaltConstraint( pParse, OE_Abort, "foreign key constraint failed", P4_STATIC ); }else{ if( nIncr>0 && pFKey->isDeferred==0 ){ sqlite3ParseToplevel(pParse)->mayAbort = 1; } sqlite3VdbeAddOp2(v, OP_FkCounter, pFKey->isDeferred, nIncr); } sqlite3VdbeResolveLabel(v, iOk); } /* ** This function is called to generate code executed when a row is deleted ** from the parent table of foreign key constraint pFKey and, if pFKey is ** deferred, when a row is inserted into the same table. When generating ** code for an SQL UPDATE operation, this function may be called twice - ** once to "delete" the old row and once to "insert" the new row. ** ** The code generated by this function scans through the rows in the child ** table that correspond to the parent table row being deleted or inserted. ** For each child row found, one of the following actions is taken: ** ** Operation | FK type | Action taken ** -------------------------------------------------------------------------- ** DELETE immediate Increment the "immediate constraint counter". ** Or, if the ON (UPDATE|DELETE) action is RESTRICT, ** throw a "foreign key constraint failed" exception. ** ** INSERT immediate Decrement the "immediate constraint counter". ** ** DELETE deferred Increment the "deferred constraint counter". ** Or, if the ON (UPDATE|DELETE) action is RESTRICT, ** throw a "foreign key constraint failed" exception. ** ** INSERT deferred Decrement the "deferred constraint counter". ** ** These operations are identified in the comment at the top of this file ** (fkey.c) as "I.2" and "D.2". */ static void fkScanChildren( Parse *pParse, /* Parse context */ SrcList *pSrc, /* SrcList containing the table to scan */ Table *pTab, Index *pIdx, /* Foreign key index */ FKey *pFKey, /* Foreign key relationship */ int *aiCol, /* Map from pIdx cols to child table cols */ int regData, /* Referenced table data starts here */ int nIncr /* Amount to increment deferred counter by */ ){ sqlite3 *db = pParse->db; /* Database handle */ int i; /* Iterator variable */ Expr *pWhere = 0; /* WHERE clause to scan with */ NameContext sNameContext; /* Context used to resolve WHERE clause */ WhereInfo *pWInfo; /* Context used by sqlite3WhereXXX() */ int iFkIfZero = 0; /* Address of OP_FkIfZero */ Vdbe *v = sqlite3GetVdbe(pParse); assert( !pIdx || pIdx->pTable==pTab ); if( nIncr<0 ){ iFkIfZero = sqlite3VdbeAddOp2(v, OP_FkIfZero, pFKey->isDeferred, 0); } /* Create an Expr object representing an SQL expression like: ** ** = AND = ... ** ** The collation sequence used for the comparison should be that of ** the parent key columns. The affinity of the parent key column should ** be applied to each child key value before the comparison takes place. */ for(i=0; inCol; i++){ Expr *pLeft; /* Value from parent table row */ Expr *pRight; /* Column ref to child table */ Expr *pEq; /* Expression (pLeft = pRight) */ int iCol; /* Index of column in child table */ const char *zCol; /* Name of column in child table */ pLeft = sqlite3Expr(db, TK_REGISTER, 0); if( pLeft ){ /* Set the collation sequence and affinity of the LHS of each TK_EQ ** expression to the parent key column defaults. */ if( pIdx ){ int iCol = pIdx->aiColumn[i]; Column *pCol = &pIdx->pTable->aCol[iCol]; pLeft->iTable = regData+iCol+1; pLeft->affinity = pCol->affinity; pLeft->pColl = sqlite3LocateCollSeq(pParse, pCol->zColl); }else{ pLeft->iTable = regData; pLeft->affinity = SQLITE_AFF_INTEGER; } } iCol = aiCol ? aiCol[i] : pFKey->aCol[0].iFrom; assert( iCol>=0 ); zCol = pFKey->pFrom->aCol[iCol].zName; pRight = sqlite3Expr(db, TK_ID, zCol); pEq = sqlite3PExpr(pParse, TK_EQ, pLeft, pRight, 0); pWhere = sqlite3ExprAnd(db, pWhere, pEq); } /* If the child table is the same as the parent table, and this scan ** is taking place as part of a DELETE operation (operation D.2), omit the ** row being deleted from the scan by adding ($rowid != rowid) to the WHERE ** clause, where $rowid is the rowid of the row being deleted. */ if( pTab==pFKey->pFrom && nIncr>0 ){ Expr *pEq; /* Expression (pLeft = pRight) */ Expr *pLeft; /* Value from parent table row */ Expr *pRight; /* Column ref to child table */ pLeft = sqlite3Expr(db, TK_REGISTER, 0); pRight = sqlite3Expr(db, TK_COLUMN, 0); if( pLeft && pRight ){ pLeft->iTable = regData; pLeft->affinity = SQLITE_AFF_INTEGER; pRight->iTable = pSrc->a[0].iCursor; pRight->iColumn = -1; } pEq = sqlite3PExpr(pParse, TK_NE, pLeft, pRight, 0); pWhere = sqlite3ExprAnd(db, pWhere, pEq); } /* Resolve the references in the WHERE clause. */ memset(&sNameContext, 0, sizeof(NameContext)); sNameContext.pSrcList = pSrc; sNameContext.pParse = pParse; sqlite3ResolveExprNames(&sNameContext, pWhere); /* Create VDBE to loop through the entries in pSrc that match the WHERE ** clause. If the constraint is not deferred, throw an exception for ** each row found. Otherwise, for deferred constraints, increment the ** deferred constraint counter by nIncr for each row selected. */ pWInfo = sqlite3WhereBegin(pParse, pSrc, pWhere, 0, 0); if( nIncr>0 && pFKey->isDeferred==0 ){ sqlite3ParseToplevel(pParse)->mayAbort = 1; } sqlite3VdbeAddOp2(v, OP_FkCounter, pFKey->isDeferred, nIncr); if( pWInfo ){ sqlite3WhereEnd(pWInfo); } /* Clean up the WHERE clause constructed above. */ sqlite3ExprDelete(db, pWhere); if( iFkIfZero ){ sqlite3VdbeJumpHere(v, iFkIfZero); } } /* ** This function returns a pointer to the head of a linked list of FK ** constraints for which table pTab is the parent table. For example, ** given the following schema: ** ** CREATE TABLE t1(a PRIMARY KEY); ** CREATE TABLE t2(b REFERENCES t1(a); ** ** Calling this function with table "t1" as an argument returns a pointer ** to the FKey structure representing the foreign key constraint on table ** "t2". Calling this function with "t2" as the argument would return a ** NULL pointer (as there are no FK constraints for which t2 is the parent ** table). */ FKey *sqlite3FkReferences(Table *pTab){ int nName = sqlite3Strlen30(pTab->zName); return (FKey *)sqlite3HashFind(&pTab->pSchema->fkeyHash, pTab->zName, nName); } /* ** The second argument is a Trigger structure allocated by the ** fkActionTrigger() routine. This function deletes the Trigger structure ** and all of its sub-components. ** ** The Trigger structure or any of its sub-components may be allocated from ** the lookaside buffer belonging to database handle dbMem. */ static void fkTriggerDelete(sqlite3 *dbMem, Trigger *p){ if( p ){ TriggerStep *pStep = p->step_list; sqlite3ExprDelete(dbMem, pStep->pWhere); sqlite3ExprListDelete(dbMem, pStep->pExprList); sqlite3SelectDelete(dbMem, pStep->pSelect); sqlite3ExprDelete(dbMem, p->pWhen); sqlite3DbFree(dbMem, p); } } /* ** This function is called to generate code that runs when table pTab is ** being dropped from the database. The SrcList passed as the second argument ** to this function contains a single entry guaranteed to resolve to ** table pTab. ** ** Normally, no code is required. However, if either ** ** (a) The table is the parent table of a FK constraint, or ** (b) The table is the child table of a deferred FK constraint and it is ** determined at runtime that there are outstanding deferred FK ** constraint violations in the database, ** ** then the equivalent of "DELETE FROM " is executed before dropping ** the table from the database. Triggers are disabled while running this ** DELETE, but foreign key actions are not. */ void sqlite3FkDropTable(Parse *pParse, SrcList *pName, Table *pTab){ sqlite3 *db = pParse->db; if( (db->flags&SQLITE_ForeignKeys) && !IsVirtual(pTab) && !pTab->pSelect ){ int iSkip = 0; Vdbe *v = sqlite3GetVdbe(pParse); assert( v ); /* VDBE has already been allocated */ if( sqlite3FkReferences(pTab)==0 ){ /* Search for a deferred foreign key constraint for which this table ** is the child table. If one cannot be found, return without ** generating any VDBE code. If one can be found, then jump over ** the entire DELETE if there are no outstanding deferred constraints ** when this statement is run. */ FKey *p; for(p=pTab->pFKey; p; p=p->pNextFrom){ if( p->isDeferred ) break; } if( !p ) return; iSkip = sqlite3VdbeMakeLabel(v); sqlite3VdbeAddOp2(v, OP_FkIfZero, 1, iSkip); } pParse->disableTriggers = 1; sqlite3DeleteFrom(pParse, sqlite3SrcListDup(db, pName, 0), 0); pParse->disableTriggers = 0; /* If the DELETE has generated immediate foreign key constraint ** violations, halt the VDBE and return an error at this point, before ** any modifications to the schema are made. This is because statement ** transactions are not able to rollback schema changes. */ sqlite3VdbeAddOp2(v, OP_FkIfZero, 0, sqlite3VdbeCurrentAddr(v)+2); sqlite3HaltConstraint( pParse, OE_Abort, "foreign key constraint failed", P4_STATIC ); if( iSkip ){ sqlite3VdbeResolveLabel(v, iSkip); } } } /* ** This function is called when inserting, deleting or updating a row of ** table pTab to generate VDBE code to perform foreign key constraint ** processing for the operation. ** ** For a DELETE operation, parameter regOld is passed the index of the ** first register in an array of (pTab->nCol+1) registers containing the ** rowid of the row being deleted, followed by each of the column values ** of the row being deleted, from left to right. Parameter regNew is passed ** zero in this case. ** ** For an INSERT operation, regOld is passed zero and regNew is passed the ** first register of an array of (pTab->nCol+1) registers containing the new ** row data. ** ** For an UPDATE operation, this function is called twice. Once before ** the original record is deleted from the table using the calling convention ** described for DELETE. Then again after the original record is deleted ** but before the new record is inserted using the INSERT convention. */ void sqlite3FkCheck( Parse *pParse, /* Parse context */ Table *pTab, /* Row is being deleted from this table */ int regOld, /* Previous row data is stored here */ int regNew /* New row data is stored here */ ){ sqlite3 *db = pParse->db; /* Database handle */ Vdbe *v; /* VM to write code to */ FKey *pFKey; /* Used to iterate through FKs */ int iDb; /* Index of database containing pTab */ const char *zDb; /* Name of database containing pTab */ int isIgnoreErrors = pParse->disableTriggers; /* Exactly one of regOld and regNew should be non-zero. */ assert( (regOld==0)!=(regNew==0) ); /* If foreign-keys are disabled, this function is a no-op. */ if( (db->flags&SQLITE_ForeignKeys)==0 ) return; v = sqlite3GetVdbe(pParse); iDb = sqlite3SchemaToIndex(db, pTab->pSchema); zDb = db->aDb[iDb].zName; /* Loop through all the foreign key constraints for which pTab is the ** child table (the table that the foreign key definition is part of). */ for(pFKey=pTab->pFKey; pFKey; pFKey=pFKey->pNextFrom){ Table *pTo; /* Parent table of foreign key pFKey */ Index *pIdx = 0; /* Index on key columns in pTo */ int *aiFree = 0; int *aiCol; int iCol; int i; /* Find the parent table of this foreign key. Also find a unique index ** on the parent key columns in the parent table. If either of these ** schema items cannot be located, set an error in pParse and return ** early. */ if( pParse->disableTriggers ){ pTo = sqlite3FindTable(db, pFKey->zTo, zDb); }else{ pTo = sqlite3LocateTable(pParse, 0, pFKey->zTo, zDb); } if( !pTo || locateFkeyIndex(pParse, pTo, pFKey, &pIdx, &aiFree) ){ if( !isIgnoreErrors || db->mallocFailed ) return; continue; } assert( pFKey->nCol==1 || (aiFree && pIdx) ); if( aiFree ){ aiCol = aiFree; }else{ iCol = pFKey->aCol[0].iFrom; aiCol = &iCol; } for(i=0; inCol; i++){ if( aiCol[i]==pTab->iPKey ){ aiCol[i] = -1; } } /* Take a shared-cache advisory read-lock on the parent table. Allocate ** a cursor to use to search the unique index on the parent key columns ** in the parent table. */ sqlite3TableLock(pParse, iDb, pTo->tnum, 0, pTo->zName); pParse->nTab++; if( regOld!=0 ){ /* A row is being removed from the child table. Search for the parent. ** If the parent does not exist, removing the child row resolves an ** outstanding foreign key constraint violation. */ fkLookupParent(pParse, iDb, pTo, pIdx, pFKey, aiCol, regOld, -1); } if( regNew!=0 ){ /* A row is being added to the child table. If a parent row cannot ** be found, adding the child row has violated the FK constraint. */ fkLookupParent(pParse, iDb, pTo, pIdx, pFKey, aiCol, regNew, +1); } sqlite3DbFree(db, aiFree); } /* Loop through all the foreign key constraints that refer to this table */ for(pFKey = sqlite3FkReferences(pTab); pFKey; pFKey=pFKey->pNextTo){ Index *pIdx = 0; /* Foreign key index for pFKey */ SrcList *pSrc; int *aiCol = 0; if( !pFKey->isDeferred && !pParse->pToplevel && !pParse->isMultiWrite ){ assert( regOld==0 && regNew!=0 ); /* Inserting a single row into a parent table cannot cause an immediate ** foreign key violation. So do nothing in this case. */ continue; } if( locateFkeyIndex(pParse, pTab, pFKey, &pIdx, &aiCol) ){ if( !isIgnoreErrors || db->mallocFailed ) return; continue; } assert( aiCol || pFKey->nCol==1 ); /* Create a SrcList structure containing a single table (the table ** the foreign key that refers to this table is attached to). This ** is required for the sqlite3WhereXXX() interface. */ pSrc = sqlite3SrcListAppend(db, 0, 0, 0); if( pSrc ){ pSrc->a->pTab = pFKey->pFrom; pSrc->a->pTab->nRef++; pSrc->a->iCursor = pParse->nTab++; if( regNew!=0 ){ fkScanChildren(pParse, pSrc, pTab, pIdx, pFKey, aiCol, regNew, -1); } if( regOld!=0 ){ /* If there is a RESTRICT action configured for the current operation ** on the parent table of this FK, then throw an exception ** immediately if the FK constraint is violated, even if this is a ** deferred trigger. That's what RESTRICT means. To defer checking ** the constraint, the FK should specify NO ACTION (represented ** using OE_None). NO ACTION is the default. */ fkScanChildren(pParse, pSrc, pTab, pIdx, pFKey, aiCol, regOld, 1); } sqlite3SrcListDelete(db, pSrc); } sqlite3DbFree(db, aiCol); } } #define COLUMN_MASK(x) (((x)>31) ? 0xffffffff : ((u32)1<<(x))) /* ** This function is called before generating code to update or delete a ** row contained in table pTab. */ u32 sqlite3FkOldmask( Parse *pParse, /* Parse context */ Table *pTab /* Table being modified */ ){ u32 mask = 0; if( pParse->db->flags&SQLITE_ForeignKeys ){ FKey *p; int i; for(p=pTab->pFKey; p; p=p->pNextFrom){ for(i=0; inCol; i++) mask |= COLUMN_MASK(p->aCol[i].iFrom); } for(p=sqlite3FkReferences(pTab); p; p=p->pNextTo){ Index *pIdx = 0; locateFkeyIndex(pParse, pTab, p, &pIdx, 0); if( pIdx ){ for(i=0; inColumn; i++) mask |= COLUMN_MASK(pIdx->aiColumn[i]); } } } return mask; } /* ** This function is called before generating code to update or delete a ** row contained in table pTab. If the operation is a DELETE, then ** parameter aChange is passed a NULL value. For an UPDATE, aChange points ** to an array of size N, where N is the number of columns in table pTab. ** If the i'th column is not modified by the UPDATE, then the corresponding ** entry in the aChange[] array is set to -1. If the column is modified, ** the value is 0 or greater. Parameter chngRowid is set to true if the ** UPDATE statement modifies the rowid fields of the table. ** ** If any foreign key processing will be required, this function returns ** true. If there is no foreign key related processing, this function ** returns false. */ int sqlite3FkRequired( Parse *pParse, /* Parse context */ Table *pTab, /* Table being modified */ int *aChange, /* Non-NULL for UPDATE operations */ int chngRowid /* True for UPDATE that affects rowid */ ){ if( pParse->db->flags&SQLITE_ForeignKeys ){ if( !aChange ){ /* A DELETE operation. Foreign key processing is required if the ** table in question is either the child or parent table for any ** foreign key constraint. */ return (sqlite3FkReferences(pTab) || pTab->pFKey); }else{ /* This is an UPDATE. Foreign key processing is only required if the ** operation modifies one or more child or parent key columns. */ int i; FKey *p; /* Check if any child key columns are being modified. */ for(p=pTab->pFKey; p; p=p->pNextFrom){ for(i=0; inCol; i++){ int iChildKey = p->aCol[i].iFrom; if( aChange[iChildKey]>=0 ) return 1; if( iChildKey==pTab->iPKey && chngRowid ) return 1; } } /* Check if any parent key columns are being modified. */ for(p=sqlite3FkReferences(pTab); p; p=p->pNextTo){ for(i=0; inCol; i++){ char *zKey = p->aCol[i].zCol; int iKey; for(iKey=0; iKeynCol; iKey++){ Column *pCol = &pTab->aCol[iKey]; if( (zKey ? !sqlite3StrICmp(pCol->zName, zKey) : pCol->isPrimKey) ){ if( aChange[iKey]>=0 ) return 1; if( iKey==pTab->iPKey && chngRowid ) return 1; } } } } } } return 0; } /* ** This function is called when an UPDATE or DELETE operation is being ** compiled on table pTab, which is the parent table of foreign-key pFKey. ** If the current operation is an UPDATE, then the pChanges parameter is ** passed a pointer to the list of columns being modified. If it is a ** DELETE, pChanges is passed a NULL pointer. ** ** It returns a pointer to a Trigger structure containing a trigger ** equivalent to the ON UPDATE or ON DELETE action specified by pFKey. ** If the action is "NO ACTION" or "RESTRICT", then a NULL pointer is ** returned (these actions require no special handling by the triggers ** sub-system, code for them is created by fkScanChildren()). ** ** For example, if pFKey is the foreign key and pTab is table "p" in ** the following schema: ** ** CREATE TABLE p(pk PRIMARY KEY); ** CREATE TABLE c(ck REFERENCES p ON DELETE CASCADE); ** ** then the returned trigger structure is equivalent to: ** ** CREATE TRIGGER ... DELETE ON p BEGIN ** DELETE FROM c WHERE ck = old.pk; ** END; ** ** The returned pointer is cached as part of the foreign key object. It ** is eventually freed along with the rest of the foreign key object by ** sqlite3FkDelete(). */ static Trigger *fkActionTrigger( Parse *pParse, /* Parse context */ Table *pTab, /* Table being updated or deleted from */ FKey *pFKey, /* Foreign key to get action for */ ExprList *pChanges /* Change-list for UPDATE, NULL for DELETE */ ){ sqlite3 *db = pParse->db; /* Database handle */ int action; /* One of OE_None, OE_Cascade etc. */ Trigger *pTrigger; /* Trigger definition to return */ int iAction = (pChanges!=0); /* 1 for UPDATE, 0 for DELETE */ action = pFKey->aAction[iAction]; pTrigger = pFKey->apTrigger[iAction]; if( action!=OE_None && !pTrigger ){ u8 enableLookaside; /* Copy of db->lookaside.bEnabled */ char const *zFrom; /* Name of child table */ int nFrom; /* Length in bytes of zFrom */ Index *pIdx = 0; /* Parent key index for this FK */ int *aiCol = 0; /* child table cols -> parent key cols */ TriggerStep *pStep; /* First (only) step of trigger program */ Expr *pWhere = 0; /* WHERE clause of trigger step */ ExprList *pList = 0; /* Changes list if ON UPDATE CASCADE */ Select *pSelect = 0; /* If RESTRICT, "SELECT RAISE(...)" */ int i; /* Iterator variable */ Expr *pWhen = 0; /* WHEN clause for the trigger */ if( locateFkeyIndex(pParse, pTab, pFKey, &pIdx, &aiCol) ) return 0; assert( aiCol || pFKey->nCol==1 ); for(i=0; inCol; i++){ Token tOld = { "old", 3 }; /* Literal "old" token */ Token tNew = { "new", 3 }; /* Literal "new" token */ Token tFromCol; /* Name of column in child table */ Token tToCol; /* Name of column in parent table */ int iFromCol; /* Idx of column in child table */ Expr *pEq; /* tFromCol = OLD.tToCol */ iFromCol = aiCol ? aiCol[i] : pFKey->aCol[0].iFrom; assert( iFromCol>=0 ); tToCol.z = pIdx ? pTab->aCol[pIdx->aiColumn[i]].zName : "oid"; tFromCol.z = pFKey->pFrom->aCol[iFromCol].zName; tToCol.n = sqlite3Strlen30(tToCol.z); tFromCol.n = sqlite3Strlen30(tFromCol.z); /* Create the expression "OLD.zToCol = zFromCol". It is important ** that the "OLD.zToCol" term is on the LHS of the = operator, so ** that the affinity and collation sequence associated with the ** parent table are used for the comparison. */ pEq = sqlite3PExpr(pParse, TK_EQ, sqlite3PExpr(pParse, TK_DOT, sqlite3PExpr(pParse, TK_ID, 0, 0, &tOld), sqlite3PExpr(pParse, TK_ID, 0, 0, &tToCol) , 0), sqlite3PExpr(pParse, TK_ID, 0, 0, &tFromCol) , 0); pWhere = sqlite3ExprAnd(db, pWhere, pEq); /* For ON UPDATE, construct the next term of the WHEN clause. ** The final WHEN clause will be like this: ** ** WHEN NOT(old.col1 IS new.col1 AND ... AND old.colN IS new.colN) */ if( pChanges ){ pEq = sqlite3PExpr(pParse, TK_IS, sqlite3PExpr(pParse, TK_DOT, sqlite3PExpr(pParse, TK_ID, 0, 0, &tOld), sqlite3PExpr(pParse, TK_ID, 0, 0, &tToCol), 0), sqlite3PExpr(pParse, TK_DOT, sqlite3PExpr(pParse, TK_ID, 0, 0, &tNew), sqlite3PExpr(pParse, TK_ID, 0, 0, &tToCol), 0), 0); pWhen = sqlite3ExprAnd(db, pWhen, pEq); } if( action!=OE_Restrict && (action!=OE_Cascade || pChanges) ){ Expr *pNew; if( action==OE_Cascade ){ pNew = sqlite3PExpr(pParse, TK_DOT, sqlite3PExpr(pParse, TK_ID, 0, 0, &tNew), sqlite3PExpr(pParse, TK_ID, 0, 0, &tToCol) , 0); }else if( action==OE_SetDflt ){ Expr *pDflt = pFKey->pFrom->aCol[iFromCol].pDflt; if( pDflt ){ pNew = sqlite3ExprDup(db, pDflt, 0); }else{ pNew = sqlite3PExpr(pParse, TK_NULL, 0, 0, 0); } }else{ pNew = sqlite3PExpr(pParse, TK_NULL, 0, 0, 0); } pList = sqlite3ExprListAppend(pParse, pList, pNew); sqlite3ExprListSetName(pParse, pList, &tFromCol, 0); } } sqlite3DbFree(db, aiCol); zFrom = pFKey->pFrom->zName; nFrom = sqlite3Strlen30(zFrom); if( action==OE_Restrict ){ Token tFrom; Expr *pRaise; tFrom.z = zFrom; tFrom.n = nFrom; pRaise = sqlite3Expr(db, TK_RAISE, "foreign key constraint failed"); if( pRaise ){ pRaise->affinity = OE_Abort; } pSelect = sqlite3SelectNew(pParse, sqlite3ExprListAppend(pParse, 0, pRaise), sqlite3SrcListAppend(db, 0, &tFrom, 0), pWhere, 0, 0, 0, 0, 0, 0 ); pWhere = 0; } /* In the current implementation, pTab->dbMem==0 for all tables except ** for temporary tables used to describe subqueries. And temporary ** tables do not have foreign key constraints. Hence, pTab->dbMem ** should always be 0 there. */ enableLookaside = db->lookaside.bEnabled; db->lookaside.bEnabled = 0; pTrigger = (Trigger *)sqlite3DbMallocZero(db, sizeof(Trigger) + /* struct Trigger */ sizeof(TriggerStep) + /* Single step in trigger program */ nFrom + 1 /* Space for pStep->target.z */ ); if( pTrigger ){ pStep = pTrigger->step_list = (TriggerStep *)&pTrigger[1]; pStep->target.z = (char *)&pStep[1]; pStep->target.n = nFrom; memcpy((char *)pStep->target.z, zFrom, nFrom); pStep->pWhere = sqlite3ExprDup(db, pWhere, EXPRDUP_REDUCE); pStep->pExprList = sqlite3ExprListDup(db, pList, EXPRDUP_REDUCE); pStep->pSelect = sqlite3SelectDup(db, pSelect, EXPRDUP_REDUCE); if( pWhen ){ pWhen = sqlite3PExpr(pParse, TK_NOT, pWhen, 0, 0); pTrigger->pWhen = sqlite3ExprDup(db, pWhen, EXPRDUP_REDUCE); } } /* Re-enable the lookaside buffer, if it was disabled earlier. */ db->lookaside.bEnabled = enableLookaside; sqlite3ExprDelete(db, pWhere); sqlite3ExprDelete(db, pWhen); sqlite3ExprListDelete(db, pList); sqlite3SelectDelete(db, pSelect); if( db->mallocFailed==1 ){ fkTriggerDelete(db, pTrigger); return 0; } switch( action ){ case OE_Restrict: pStep->op = TK_SELECT; break; case OE_Cascade: if( !pChanges ){ pStep->op = TK_DELETE; break; } default: pStep->op = TK_UPDATE; } pStep->pTrig = pTrigger; pTrigger->pSchema = pTab->pSchema; pTrigger->pTabSchema = pTab->pSchema; pFKey->apTrigger[iAction] = pTrigger; pTrigger->op = (pChanges ? TK_UPDATE : TK_DELETE); } return pTrigger; } /* ** This function is called when deleting or updating a row to implement ** any required CASCADE, SET NULL or SET DEFAULT actions. */ void sqlite3FkActions( Parse *pParse, /* Parse context */ Table *pTab, /* Table being updated or deleted from */ ExprList *pChanges, /* Change-list for UPDATE, NULL for DELETE */ int regOld /* Address of array containing old row */ ){ /* If foreign-key support is enabled, iterate through all FKs that ** refer to table pTab. If there is an action associated with the FK ** for this operation (either update or delete), invoke the associated ** trigger sub-program. */ if( pParse->db->flags&SQLITE_ForeignKeys ){ FKey *pFKey; /* Iterator variable */ for(pFKey = sqlite3FkReferences(pTab); pFKey; pFKey=pFKey->pNextTo){ Trigger *pAction = fkActionTrigger(pParse, pTab, pFKey, pChanges); if( pAction ){ sqlite3CodeRowTriggerDirect(pParse, pAction, pTab, regOld, OE_Abort, 0); } } } } #endif /* ifndef SQLITE_OMIT_TRIGGER */ /* ** Free all memory associated with foreign key definitions attached to ** table pTab. Remove the deleted foreign keys from the Schema.fkeyHash ** hash table. */ void sqlite3FkDelete(Table *pTab){ FKey *pFKey; /* Iterator variable */ FKey *pNext; /* Copy of pFKey->pNextFrom */ for(pFKey=pTab->pFKey; pFKey; pFKey=pNext){ /* Remove the FK from the fkeyHash hash table. */ if( pFKey->pPrevTo ){ pFKey->pPrevTo->pNextTo = pFKey->pNextTo; }else{ void *data = (void *)pFKey->pNextTo; const char *z = (data ? pFKey->pNextTo->zTo : pFKey->zTo); sqlite3HashInsert(&pTab->pSchema->fkeyHash, z, sqlite3Strlen30(z), data); } if( pFKey->pNextTo ){ pFKey->pNextTo->pPrevTo = pFKey->pPrevTo; } /* Delete any triggers created to implement actions for this FK. */ #ifndef SQLITE_OMIT_TRIGGER fkTriggerDelete(pTab->dbMem, pFKey->apTrigger[0]); fkTriggerDelete(pTab->dbMem, pFKey->apTrigger[1]); #endif /* Delete the memory allocated for the FK structure. */ pNext = pFKey->pNextFrom; sqlite3DbFree(pTab->dbMem, pFKey); } } #endif /* ifndef SQLITE_OMIT_FOREIGN_KEY */