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Diffstat (limited to 'src/fkey.c')
| -rw-r--r-- | src/fkey.c | 1475 |
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diff --git a/src/fkey.c b/src/fkey.c new file mode 100644 index 0000000..cae6bb1 --- /dev/null +++ b/src/fkey.c @@ -0,0 +1,1475 @@ +/* +** +** 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_FOREIGNKEY 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_FOREIGNKEY +** 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 for 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 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. +*/ +int sqlite3FkLocateIndex( + 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].zCnName, zKey) ){ + return 0; + } + } + }else if( paiCol ){ + assert( nCol>1 ); + aiCol = (int *)sqlite3DbMallocRawNN(pParse->db, nCol*sizeof(int)); + if( !aiCol ) return 1; + *paiCol = aiCol; + } + + for(pIdx=pParent->pIndex; pIdx; pIdx=pIdx->pNext){ + if( pIdx->nKeyCol==nCol && IsUniqueIndex(pIdx) && pIdx->pPartIdxWhere==0 ){ + /* 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. */ + if( IsPrimaryKeyIndex(pIdx) ){ + if( aiCol ){ + int i; + for(i=0; i<nCol; i++) aiCol[i] = pFKey->aCol[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; i<nCol; i++){ + i16 iCol = pIdx->aiColumn[i]; /* Index of column in parent tbl */ + const char *zDfltColl; /* Def. collation for column */ + char *zIdxCol; /* Name of indexed column */ + + if( iCol<0 ) break; /* No foreign keys against expression indexes */ + + /* 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 = sqlite3ColumnColl(&pParent->aCol[iCol]); + if( !zDfltColl ) zDfltColl = sqlite3StrBINARY; + if( sqlite3StrICmp(pIdx->azColl[i], zDfltColl) ) break; + + zIdxCol = pParent->aCol[iCol].zCnName; + for(j=0; j<nCol; j++){ + if( sqlite3StrICmp(pFKey->aCol[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 - \"%w\" referencing \"%w\"", + pFKey->pFrom->zName, pFKey->zTo); + } + 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 isIgnore /* If true, pretend pTab contains all NULL values */ +){ + 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(pParse); /* jump here if parent key found */ + + sqlite3VdbeVerifyAbortable(v, + (!pFKey->isDeferred + && !(pParse->db->flags & SQLITE_DeferFKs) + && !pParse->pToplevel + && !pParse->isMultiWrite) ? OE_Abort : OE_Ignore); + + /* 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); + VdbeCoverage(v); + } + for(i=0; i<pFKey->nCol; i++){ + int iReg = sqlite3TableColumnToStorage(pFKey->pFrom,aiCol[i]) + regData + 1; + sqlite3VdbeAddOp2(v, OP_IsNull, iReg, iOk); VdbeCoverage(v); + } + + if( isIgnore==0 ){ + 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, + sqlite3TableColumnToStorage(pFKey->pFrom,aiCol[0])+1+regData, regTemp); + iMustBeInt = sqlite3VdbeAddOp2(v, OP_MustBeInt, regTemp, 0); + VdbeCoverage(v); + + /* 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); VdbeCoverage(v); + sqlite3VdbeChangeP5(v, SQLITE_NOTNULL); + } + + sqlite3OpenTable(pParse, iCur, iDb, pTab, OP_OpenRead); + sqlite3VdbeAddOp3(v, OP_NotExists, iCur, 0, regTemp); VdbeCoverage(v); + sqlite3VdbeGoto(v, iOk); + sqlite3VdbeJumpHere(v, sqlite3VdbeCurrentAddr(v)-2); + sqlite3VdbeJumpHere(v, iMustBeInt); + sqlite3ReleaseTempReg(pParse, regTemp); + }else{ + int nCol = pFKey->nCol; + int regTemp = sqlite3GetTempRange(pParse, nCol); + + sqlite3VdbeAddOp3(v, OP_OpenRead, iCur, pIdx->tnum, iDb); + sqlite3VdbeSetP4KeyInfo(pParse, pIdx); + for(i=0; i<nCol; i++){ + sqlite3VdbeAddOp2(v, OP_Copy, + sqlite3TableColumnToStorage(pFKey->pFrom, aiCol[i])+1+regData, + regTemp+i); + } + + /* 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 any of the parent-key values are NULL, then the row cannot match + ** itself. So set JUMPIFNULL to make sure we do the OP_Found if any + ** of the parent-key values are NULL (at this point it is known that + ** none of the child key values are). + */ + if( pTab==pFKey->pFrom && nIncr==1 ){ + int iJump = sqlite3VdbeCurrentAddr(v) + nCol + 1; + for(i=0; i<nCol; i++){ + int iChild = sqlite3TableColumnToStorage(pFKey->pFrom,aiCol[i]) + +1+regData; + int iParent = 1+regData; + iParent += sqlite3TableColumnToStorage(pIdx->pTable, + pIdx->aiColumn[i]); + assert( pIdx->aiColumn[i]>=0 ); + assert( aiCol[i]!=pTab->iPKey ); + if( pIdx->aiColumn[i]==pTab->iPKey ){ + /* The parent key is a composite key that includes the IPK column */ + iParent = regData; + } + sqlite3VdbeAddOp3(v, OP_Ne, iChild, iJump, iParent); VdbeCoverage(v); + sqlite3VdbeChangeP5(v, SQLITE_JUMPIFNULL); + } + sqlite3VdbeGoto(v, iOk); + } + + sqlite3VdbeAddOp4(v, OP_Affinity, regTemp, nCol, 0, + sqlite3IndexAffinityStr(pParse->db,pIdx), nCol); + sqlite3VdbeAddOp4Int(v, OP_Found, iCur, iOk, regTemp, nCol); + VdbeCoverage(v); + sqlite3ReleaseTempRange(pParse, regTemp, nCol); + } + } + + if( !pFKey->isDeferred && !(pParse->db->flags & SQLITE_DeferFKs) + && !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, SQLITE_CONSTRAINT_FOREIGNKEY, + OE_Abort, 0, P4_STATIC, P5_ConstraintFK); + }else{ + if( nIncr>0 && pFKey->isDeferred==0 ){ + sqlite3MayAbort(pParse); + } + sqlite3VdbeAddOp2(v, OP_FkCounter, pFKey->isDeferred, nIncr); + } + + sqlite3VdbeResolveLabel(v, iOk); + sqlite3VdbeAddOp1(v, OP_Close, iCur); +} + + +/* +** Return an Expr object that refers to a memory register corresponding +** to column iCol of table pTab. +** +** regBase is the first of an array of register that contains the data +** for pTab. regBase itself holds the rowid. regBase+1 holds the first +** column. regBase+2 holds the second column, and so forth. +*/ +static Expr *exprTableRegister( + Parse *pParse, /* Parsing and code generating context */ + Table *pTab, /* The table whose content is at r[regBase]... */ + int regBase, /* Contents of table pTab */ + i16 iCol /* Which column of pTab is desired */ +){ + Expr *pExpr; + Column *pCol; + const char *zColl; + sqlite3 *db = pParse->db; + + pExpr = sqlite3Expr(db, TK_REGISTER, 0); + if( pExpr ){ + if( iCol>=0 && iCol!=pTab->iPKey ){ + pCol = &pTab->aCol[iCol]; + pExpr->iTable = regBase + sqlite3TableColumnToStorage(pTab,iCol) + 1; + pExpr->affExpr = pCol->affinity; + zColl = sqlite3ColumnColl(pCol); + if( zColl==0 ) zColl = db->pDfltColl->zName; + pExpr = sqlite3ExprAddCollateString(pParse, pExpr, zColl); + }else{ + pExpr->iTable = regBase; + pExpr->affExpr = SQLITE_AFF_INTEGER; + } + } + return pExpr; +} + +/* +** Return an Expr object that refers to column iCol of table pTab which +** has cursor iCur. +*/ +static Expr *exprTableColumn( + sqlite3 *db, /* The database connection */ + Table *pTab, /* The table whose column is desired */ + int iCursor, /* The open cursor on the table */ + i16 iCol /* The column that is wanted */ +){ + Expr *pExpr = sqlite3Expr(db, TK_COLUMN, 0); + if( pExpr ){ + assert( ExprUseYTab(pExpr) ); + pExpr->y.pTab = pTab; + pExpr->iTable = iCursor; + pExpr->iColumn = iCol; + } + return pExpr; +} + +/* +** 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. +** +** Parameter nIncr is passed -1 when inserting a row (as this may decrease +** the number of FK violations in the db) or +1 when deleting one (as this +** may increase the number of FK constraint problems). +** +** 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". +** +** INSERT immediate Decrement the "immediate constraint counter". +** +** DELETE deferred Increment the "deferred constraint counter". +** +** 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, /* The child table to be scanned */ + Table *pTab, /* The parent table */ + Index *pIdx, /* Index on parent covering the foreign key */ + FKey *pFKey, /* The foreign key linking pSrc to pTab */ + int *aiCol, /* Map from pIdx cols to child table cols */ + int regData, /* Parent row 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==0 || pIdx->pTable==pTab ); + assert( pIdx==0 || pIdx->nKeyCol==pFKey->nCol ); + assert( pIdx!=0 || pFKey->nCol==1 ); + assert( pIdx!=0 || HasRowid(pTab) ); + + if( nIncr<0 ){ + iFkIfZero = sqlite3VdbeAddOp2(v, OP_FkIfZero, pFKey->isDeferred, 0); + VdbeCoverage(v); + } + + /* Create an Expr object representing an SQL expression like: + ** + ** <parent-key1> = <child-key1> AND <parent-key2> = <child-key2> ... + ** + ** 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; i<pFKey->nCol; i++){ + Expr *pLeft; /* Value from parent table row */ + Expr *pRight; /* Column ref to child table */ + Expr *pEq; /* Expression (pLeft = pRight) */ + i16 iCol; /* Index of column in child table */ + const char *zCol; /* Name of column in child table */ + + iCol = pIdx ? pIdx->aiColumn[i] : -1; + pLeft = exprTableRegister(pParse, pTab, regData, iCol); + iCol = aiCol ? aiCol[i] : pFKey->aCol[0].iFrom; + assert( iCol>=0 ); + zCol = pFKey->pFrom->aCol[iCol].zCnName; + pRight = sqlite3Expr(db, TK_ID, zCol); + pEq = sqlite3PExpr(pParse, TK_EQ, pLeft, pRight); + pWhere = sqlite3ExprAnd(pParse, pWhere, pEq); + } + + /* If the child table is the same as the parent table, then add terms + ** to the WHERE clause that prevent this entry from being scanned. + ** The added WHERE clause terms are like this: + ** + ** $current_rowid!=rowid + ** NOT( $current_a==a AND $current_b==b AND ... ) + ** + ** The first form is used for rowid tables. The second form is used + ** for WITHOUT ROWID tables. In the second form, the *parent* key is + ** (a,b,...). Either the parent or primary key could be used to + ** uniquely identify the current row, but the parent key is more convenient + ** as the required values have already been loaded into registers + ** by the caller. + */ + if( pTab==pFKey->pFrom && nIncr>0 ){ + Expr *pNe; /* Expression (pLeft != pRight) */ + Expr *pLeft; /* Value from parent table row */ + Expr *pRight; /* Column ref to child table */ + if( HasRowid(pTab) ){ + pLeft = exprTableRegister(pParse, pTab, regData, -1); + pRight = exprTableColumn(db, pTab, pSrc->a[0].iCursor, -1); + pNe = sqlite3PExpr(pParse, TK_NE, pLeft, pRight); + }else{ + Expr *pEq, *pAll = 0; + assert( pIdx!=0 ); + for(i=0; i<pIdx->nKeyCol; i++){ + i16 iCol = pIdx->aiColumn[i]; + assert( iCol>=0 ); + pLeft = exprTableRegister(pParse, pTab, regData, iCol); + pRight = sqlite3Expr(db, TK_ID, pTab->aCol[iCol].zCnName); + pEq = sqlite3PExpr(pParse, TK_IS, pLeft, pRight); + pAll = sqlite3ExprAnd(pParse, pAll, pEq); + } + pNe = sqlite3PExpr(pParse, TK_NOT, pAll, 0); + } + pWhere = sqlite3ExprAnd(pParse, pWhere, pNe); + } + + /* 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. For each row found, increment either the deferred or immediate + ** foreign key constraint counter. */ + if( pParse->nErr==0 ){ + pWInfo = sqlite3WhereBegin(pParse, pSrc, pWhere, 0, 0, 0, 0, 0); + sqlite3VdbeAddOp2(v, OP_FkCounter, pFKey->isDeferred, nIncr); + if( pWInfo ){ + sqlite3WhereEnd(pWInfo); + } + } + + /* Clean up the WHERE clause constructed above. */ + sqlite3ExprDelete(db, pWhere); + if( iFkIfZero ){ + sqlite3VdbeJumpHereOrPopInst(v, iFkIfZero); + } +} + +/* +** This function returns a linked list of FKey objects (connected by +** FKey.pNextTo) holding all children of table pTab. 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){ + return (FKey *)sqlite3HashFind(&pTab->pSchema->fkeyHash, pTab->zName); +} + +/* +** 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); + } +} + +/* +** Clear the apTrigger[] cache of CASCADE triggers for all foreign keys +** in a particular database. This needs to happen when the schema +** changes. +*/ +void sqlite3FkClearTriggerCache(sqlite3 *db, int iDb){ + HashElem *k; + Hash *pHash = &db->aDb[iDb].pSchema->tblHash; + for(k=sqliteHashFirst(pHash); k; k=sqliteHashNext(k)){ + Table *pTab = sqliteHashData(k); + FKey *pFKey; + if( !IsOrdinaryTable(pTab) ) continue; + for(pFKey=pTab->u.tab.pFKey; pFKey; pFKey=pFKey->pNextFrom){ + fkTriggerDelete(db, pFKey->apTrigger[0]); pFKey->apTrigger[0] = 0; + fkTriggerDelete(db, pFKey->apTrigger[1]); pFKey->apTrigger[1] = 0; + } + } +} + +/* +** 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 <tbl>" 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) && IsOrdinaryTable(pTab) ){ + int iSkip = 0; + Vdbe *v = sqlite3GetVdbe(pParse); + + assert( v ); /* VDBE has already been allocated */ + assert( IsOrdinaryTable(pTab) ); + 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->u.tab.pFKey; p; p=p->pNextFrom){ + if( p->isDeferred || (db->flags & SQLITE_DeferFKs) ) break; + } + if( !p ) return; + iSkip = sqlite3VdbeMakeLabel(pParse); + sqlite3VdbeAddOp2(v, OP_FkIfZero, 1, iSkip); VdbeCoverage(v); + } + + pParse->disableTriggers = 1; + sqlite3DeleteFrom(pParse, sqlite3SrcListDup(db, pName, 0), 0, 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. + ** + ** If the SQLITE_DeferFKs flag is set, then this is not required, as + ** the statement transaction will not be rolled back even if FK + ** constraints are violated. + */ + if( (db->flags & SQLITE_DeferFKs)==0 ){ + sqlite3VdbeVerifyAbortable(v, OE_Abort); + sqlite3VdbeAddOp2(v, OP_FkIfZero, 0, sqlite3VdbeCurrentAddr(v)+2); + VdbeCoverage(v); + sqlite3HaltConstraint(pParse, SQLITE_CONSTRAINT_FOREIGNKEY, + OE_Abort, 0, P4_STATIC, P5_ConstraintFK); + } + + if( iSkip ){ + sqlite3VdbeResolveLabel(v, iSkip); + } + } +} + + +/* +** The second argument points to an FKey object representing a foreign key +** for which pTab is the child table. An UPDATE statement against pTab +** is currently being processed. For each column of the table that is +** actually updated, the corresponding element in the aChange[] array +** is zero or greater (if a column is unmodified the corresponding element +** is set to -1). If the rowid column is modified by the UPDATE statement +** the bChngRowid argument is non-zero. +** +** This function returns true if any of the columns that are part of the +** child key for FK constraint *p are modified. +*/ +static int fkChildIsModified( + Table *pTab, /* Table being updated */ + FKey *p, /* Foreign key for which pTab is the child */ + int *aChange, /* Array indicating modified columns */ + int bChngRowid /* True if rowid is modified by this update */ +){ + int i; + for(i=0; i<p->nCol; i++){ + int iChildKey = p->aCol[i].iFrom; + if( aChange[iChildKey]>=0 ) return 1; + if( iChildKey==pTab->iPKey && bChngRowid ) return 1; + } + return 0; +} + +/* +** The second argument points to an FKey object representing a foreign key +** for which pTab is the parent table. An UPDATE statement against pTab +** is currently being processed. For each column of the table that is +** actually updated, the corresponding element in the aChange[] array +** is zero or greater (if a column is unmodified the corresponding element +** is set to -1). If the rowid column is modified by the UPDATE statement +** the bChngRowid argument is non-zero. +** +** This function returns true if any of the columns that are part of the +** parent key for FK constraint *p are modified. +*/ +static int fkParentIsModified( + Table *pTab, + FKey *p, + int *aChange, + int bChngRowid +){ + int i; + for(i=0; i<p->nCol; i++){ + char *zKey = p->aCol[i].zCol; + int iKey; + for(iKey=0; iKey<pTab->nCol; iKey++){ + if( aChange[iKey]>=0 || (iKey==pTab->iPKey && bChngRowid) ){ + Column *pCol = &pTab->aCol[iKey]; + if( zKey ){ + if( 0==sqlite3StrICmp(pCol->zCnName, zKey) ) return 1; + }else if( pCol->colFlags & COLFLAG_PRIMKEY ){ + return 1; + } + } + } + } + return 0; +} + +/* +** Return true if the parser passed as the first argument is being +** used to code a trigger that is really a "SET NULL" action belonging +** to trigger pFKey. +*/ +static int isSetNullAction(Parse *pParse, FKey *pFKey){ + Parse *pTop = sqlite3ParseToplevel(pParse); + if( pTop->pTriggerPrg ){ + Trigger *p = pTop->pTriggerPrg->pTrigger; + if( (p==pFKey->apTrigger[0] && pFKey->aAction[0]==OE_SetNull) + || (p==pFKey->apTrigger[1] && pFKey->aAction[1]==OE_SetNull) + ){ + return 1; + } + } + return 0; +} + +/* +** 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 */ + int *aChange, /* Array indicating UPDATEd columns (or 0) */ + int bChngRowid /* True if rowid is UPDATEd */ +){ + sqlite3 *db = pParse->db; /* Database handle */ + 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; + if( !IsOrdinaryTable(pTab) ) return; + + iDb = sqlite3SchemaToIndex(db, pTab->pSchema); + zDb = db->aDb[iDb].zDbSName; + + /* 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->u.tab.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; + int bIgnore = 0; + + if( aChange + && sqlite3_stricmp(pTab->zName, pFKey->zTo)!=0 + && fkChildIsModified(pTab, pFKey, aChange, bChngRowid)==0 + ){ + continue; + } + + /* 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 || sqlite3FkLocateIndex(pParse, pTo, pFKey, &pIdx, &aiFree) ){ + assert( isIgnoreErrors==0 || (regOld!=0 && regNew==0) ); + if( !isIgnoreErrors || db->mallocFailed ) return; + if( pTo==0 ){ + /* If isIgnoreErrors is true, then a table is being dropped. In this + ** case SQLite runs a "DELETE FROM xxx" on the table being dropped + ** before actually dropping it in order to check FK constraints. + ** If the parent table of an FK constraint on the current table is + ** missing, behave as if it is empty. i.e. decrement the relevant + ** FK counter for each row of the current table with non-NULL keys. + */ + Vdbe *v = sqlite3GetVdbe(pParse); + int iJump = sqlite3VdbeCurrentAddr(v) + pFKey->nCol + 1; + for(i=0; i<pFKey->nCol; i++){ + int iFromCol, iReg; + iFromCol = pFKey->aCol[i].iFrom; + iReg = sqlite3TableColumnToStorage(pFKey->pFrom,iFromCol) + regOld+1; + sqlite3VdbeAddOp2(v, OP_IsNull, iReg, iJump); VdbeCoverage(v); + } + sqlite3VdbeAddOp2(v, OP_FkCounter, pFKey->isDeferred, -1); + } + continue; + } + assert( pFKey->nCol==1 || (aiFree && pIdx) ); + + if( aiFree ){ + aiCol = aiFree; + }else{ + iCol = pFKey->aCol[0].iFrom; + aiCol = &iCol; + } + for(i=0; i<pFKey->nCol; i++){ + if( aiCol[i]==pTab->iPKey ){ + aiCol[i] = -1; + } + assert( pIdx==0 || pIdx->aiColumn[i]>=0 ); +#ifndef SQLITE_OMIT_AUTHORIZATION + /* Request permission to read the parent key columns. If the + ** authorization callback returns SQLITE_IGNORE, behave as if any + ** values read from the parent table are NULL. */ + if( db->xAuth ){ + int rcauth; + char *zCol = pTo->aCol[pIdx ? pIdx->aiColumn[i] : pTo->iPKey].zCnName; + rcauth = sqlite3AuthReadCol(pParse, pTo->zName, zCol, iDb); + bIgnore = (rcauth==SQLITE_IGNORE); + } +#endif + } + + /* 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, bIgnore); + } + if( regNew!=0 && !isSetNullAction(pParse, pFKey) ){ + /* 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. + ** + ** If this operation is being performed as part of a trigger program + ** that is actually a "SET NULL" action belonging to this very + ** foreign key, then omit this scan altogether. As all child key + ** values are guaranteed to be NULL, it is not possible for adding + ** this row to cause an FK violation. */ + fkLookupParent(pParse, iDb, pTo, pIdx, pFKey, aiCol, regNew, +1, bIgnore); + } + + sqlite3DbFree(db, aiFree); + } + + /* Loop through all the foreign key constraints that refer to this table. + ** (the "child" constraints) */ + for(pFKey = sqlite3FkReferences(pTab); pFKey; pFKey=pFKey->pNextTo){ + Index *pIdx = 0; /* Foreign key index for pFKey */ + SrcList *pSrc; + int *aiCol = 0; + + if( aChange && fkParentIsModified(pTab, pFKey, aChange, bChngRowid)==0 ){ + continue; + } + + if( !pFKey->isDeferred && !(db->flags & SQLITE_DeferFKs) + && !pParse->pToplevel && !pParse->isMultiWrite + ){ + assert( regOld==0 && regNew!=0 ); + /* Inserting a single row into a parent table cannot cause (or fix) + ** an immediate foreign key violation. So do nothing in this case. */ + continue; + } + + if( sqlite3FkLocateIndex(pParse, pTab, pFKey, &pIdx, &aiCol) ){ + if( !isIgnoreErrors || db->mallocFailed ) return; + continue; + } + assert( aiCol || pFKey->nCol==1 ); + + /* Create a SrcList structure containing the child table. We need the + ** child table as a SrcList for sqlite3WhereBegin() */ + pSrc = sqlite3SrcListAppend(pParse, 0, 0, 0); + if( pSrc ){ + SrcItem *pItem = pSrc->a; + pItem->pTab = pFKey->pFrom; + pItem->zName = pFKey->pFrom->zName; + pItem->pTab->nTabRef++; + pItem->iCursor = pParse->nTab++; + + if( regNew!=0 ){ + fkScanChildren(pParse, pSrc, pTab, pIdx, pFKey, aiCol, regNew, -1); + } + if( regOld!=0 ){ + int eAction = pFKey->aAction[aChange!=0]; + fkScanChildren(pParse, pSrc, pTab, pIdx, pFKey, aiCol, regOld, 1); + /* If this is a deferred FK constraint, or a CASCADE or SET NULL + ** action applies, then any foreign key violations caused by + ** removing the parent key will be rectified by the action trigger. + ** So do not set the "may-abort" flag in this case. + ** + ** Note 1: If the FK is declared "ON UPDATE CASCADE", then the + ** may-abort flag will eventually be set on this statement anyway + ** (when this function is called as part of processing the UPDATE + ** within the action trigger). + ** + ** Note 2: At first glance it may seem like SQLite could simply omit + ** all OP_FkCounter related scans when either CASCADE or SET NULL + ** applies. The trouble starts if the CASCADE or SET NULL action + ** trigger causes other triggers or action rules attached to the + ** child table to fire. In these cases the fk constraint counters + ** might be set incorrectly if any OP_FkCounter related scans are + ** omitted. */ + if( !pFKey->isDeferred && eAction!=OE_Cascade && eAction!=OE_SetNull ){ + sqlite3MayAbort(pParse); + } + } + pItem->zName = 0; + 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 && IsOrdinaryTable(pTab) ){ + FKey *p; + int i; + for(p=pTab->u.tab.pFKey; p; p=p->pNextFrom){ + for(i=0; i<p->nCol; i++) mask |= COLUMN_MASK(p->aCol[i].iFrom); + } + for(p=sqlite3FkReferences(pTab); p; p=p->pNextTo){ + Index *pIdx = 0; + sqlite3FkLocateIndex(pParse, pTab, p, &pIdx, 0); + if( pIdx ){ + for(i=0; i<pIdx->nKeyCol; i++){ + assert( pIdx->aiColumn[i]>=0 ); + 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 +** non-zero. If there is no foreign key related processing, this function +** returns zero. +** +** For an UPDATE, this function returns 2 if: +** +** * There are any FKs for which pTab is the child and the parent table +** and any FK processing at all is required (even of a different FK), or +** +** * the UPDATE modifies one or more parent keys for which the action is +** not "NO ACTION" (i.e. is CASCADE, SET DEFAULT or SET NULL). +** +** Or, assuming some other foreign key processing is required, 1. +*/ +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 */ +){ + int eRet = 1; /* Value to return if bHaveFK is true */ + int bHaveFK = 0; /* If FK processing is required */ + if( pParse->db->flags&SQLITE_ForeignKeys && IsOrdinaryTable(pTab) ){ + 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. */ + bHaveFK = (sqlite3FkReferences(pTab) || pTab->u.tab.pFKey); + }else{ + /* This is an UPDATE. Foreign key processing is only required if the + ** operation modifies one or more child or parent key columns. */ + FKey *p; + + /* Check if any child key columns are being modified. */ + for(p=pTab->u.tab.pFKey; p; p=p->pNextFrom){ + if( fkChildIsModified(pTab, p, aChange, chngRowid) ){ + if( 0==sqlite3_stricmp(pTab->zName, p->zTo) ) eRet = 2; + bHaveFK = 1; + } + } + + /* Check if any parent key columns are being modified. */ + for(p=sqlite3FkReferences(pTab); p; p=p->pNextTo){ + if( fkParentIsModified(pTab, p, aChange, chngRowid) ){ + if( p->aAction[1]!=OE_None ) return 2; + bHaveFK = 1; + } + } + } + } + return bHaveFK ? eRet : 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" 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]; + if( action==OE_Restrict && (db->flags & SQLITE_DeferFKs) ){ + return 0; + } + pTrigger = pFKey->apTrigger[iAction]; + + if( action!=OE_None && !pTrigger ){ + 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 = 0; /* 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( sqlite3FkLocateIndex(pParse, pTab, pFKey, &pIdx, &aiCol) ) return 0; + assert( aiCol || pFKey->nCol==1 ); + + for(i=0; i<pFKey->nCol; 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 ); + assert( pIdx!=0 || (pTab->iPKey>=0 && pTab->iPKey<pTab->nCol) ); + assert( pIdx==0 || pIdx->aiColumn[i]>=0 ); + sqlite3TokenInit(&tToCol, + pTab->aCol[pIdx ? pIdx->aiColumn[i] : pTab->iPKey].zCnName); + sqlite3TokenInit(&tFromCol, pFKey->pFrom->aCol[iFromCol].zCnName); + + /* 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, + sqlite3ExprAlloc(db, TK_ID, &tOld, 0), + sqlite3ExprAlloc(db, TK_ID, &tToCol, 0)), + sqlite3ExprAlloc(db, TK_ID, &tFromCol, 0) + ); + pWhere = sqlite3ExprAnd(pParse, 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, + sqlite3ExprAlloc(db, TK_ID, &tOld, 0), + sqlite3ExprAlloc(db, TK_ID, &tToCol, 0)), + sqlite3PExpr(pParse, TK_DOT, + sqlite3ExprAlloc(db, TK_ID, &tNew, 0), + sqlite3ExprAlloc(db, TK_ID, &tToCol, 0)) + ); + pWhen = sqlite3ExprAnd(pParse, pWhen, pEq); + } + + if( action!=OE_Restrict && (action!=OE_Cascade || pChanges) ){ + Expr *pNew; + if( action==OE_Cascade ){ + pNew = sqlite3PExpr(pParse, TK_DOT, + sqlite3ExprAlloc(db, TK_ID, &tNew, 0), + sqlite3ExprAlloc(db, TK_ID, &tToCol, 0)); + }else if( action==OE_SetDflt ){ + Column *pCol = pFKey->pFrom->aCol + iFromCol; + Expr *pDflt; + if( pCol->colFlags & COLFLAG_GENERATED ){ + testcase( pCol->colFlags & COLFLAG_VIRTUAL ); + testcase( pCol->colFlags & COLFLAG_STORED ); + pDflt = 0; + }else{ + pDflt = sqlite3ColumnExpr(pFKey->pFrom, pCol); + } + if( pDflt ){ + pNew = sqlite3ExprDup(db, pDflt, 0); + }else{ + pNew = sqlite3ExprAlloc(db, TK_NULL, 0, 0); + } + }else{ + pNew = sqlite3ExprAlloc(db, TK_NULL, 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 ){ + int iDb = sqlite3SchemaToIndex(db, pTab->pSchema); + Token tFrom; + Token tDb; + Expr *pRaise; + + tFrom.z = zFrom; + tFrom.n = nFrom; + tDb.z = db->aDb[iDb].zDbSName; + tDb.n = sqlite3Strlen30(tDb.z); + + pRaise = sqlite3Expr(db, TK_RAISE, "FOREIGN KEY constraint failed"); + if( pRaise ){ + pRaise->affExpr = OE_Abort; + } + pSelect = sqlite3SelectNew(pParse, + sqlite3ExprListAppend(pParse, 0, pRaise), + sqlite3SrcListAppend(pParse, 0, &tDb, &tFrom), + pWhere, + 0, 0, 0, 0, 0 + ); + pWhere = 0; + } + + /* Disable lookaside memory allocation */ + DisableLookaside; + + pTrigger = (Trigger *)sqlite3DbMallocZero(db, + sizeof(Trigger) + /* struct Trigger */ + sizeof(TriggerStep) + /* Single step in trigger program */ + nFrom + 1 /* Space for pStep->zTarget */ + ); + if( pTrigger ){ + pStep = pTrigger->step_list = (TriggerStep *)&pTrigger[1]; + pStep->zTarget = (char *)&pStep[1]; + memcpy((char *)pStep->zTarget, 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); + pTrigger->pWhen = sqlite3ExprDup(db, pWhen, EXPRDUP_REDUCE); + } + } + + /* Re-enable the lookaside buffer, if it was disabled earlier. */ + EnableLookaside; + + sqlite3ExprDelete(db, pWhere); + sqlite3ExprDelete(db, pWhen); + sqlite3ExprListDelete(db, pList); + sqlite3SelectDelete(db, pSelect); + if( db->mallocFailed==1 ){ + fkTriggerDelete(db, pTrigger); + return 0; + } + assert( pStep!=0 ); + assert( pTrigger!=0 ); + + switch( action ){ + case OE_Restrict: + pStep->op = TK_SELECT; + break; + case OE_Cascade: + if( !pChanges ){ + pStep->op = TK_DELETE; + break; + } + /* no break */ deliberate_fall_through + 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 */ + int *aChange, /* Array indicating UPDATEd columns (or 0) */ + int bChngRowid /* True if rowid is UPDATEd */ +){ + /* 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){ + if( aChange==0 || fkParentIsModified(pTab, pFKey, aChange, bChngRowid) ){ + Trigger *pAct = fkActionTrigger(pParse, pTab, pFKey, pChanges); + if( pAct ){ + sqlite3CodeRowTriggerDirect(pParse, pAct, 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(sqlite3 *db, Table *pTab){ + FKey *pFKey; /* Iterator variable */ + FKey *pNext; /* Copy of pFKey->pNextFrom */ + + assert( IsOrdinaryTable(pTab) ); + assert( db!=0 ); + for(pFKey=pTab->u.tab.pFKey; pFKey; pFKey=pNext){ + assert( db==0 || sqlite3SchemaMutexHeld(db, 0, pTab->pSchema) ); + + /* Remove the FK from the fkeyHash hash table. */ + if( db->pnBytesFreed==0 ){ + if( pFKey->pPrevTo ){ + pFKey->pPrevTo->pNextTo = pFKey->pNextTo; + }else{ + void *p = (void *)pFKey->pNextTo; + const char *z = (p ? pFKey->pNextTo->zTo : pFKey->zTo); + sqlite3HashInsert(&pTab->pSchema->fkeyHash, z, p); + } + if( pFKey->pNextTo ){ + pFKey->pNextTo->pPrevTo = pFKey->pPrevTo; + } + } + + /* EV: R-30323-21917 Each foreign key constraint in SQLite is + ** classified as either immediate or deferred. + */ + assert( pFKey->isDeferred==0 || pFKey->isDeferred==1 ); + + /* Delete any triggers created to implement actions for this FK. */ +#ifndef SQLITE_OMIT_TRIGGER + fkTriggerDelete(db, pFKey->apTrigger[0]); + fkTriggerDelete(db, pFKey->apTrigger[1]); +#endif + + pNext = pFKey->pNextFrom; + sqlite3DbFree(db, pFKey); + } +} +#endif /* ifndef SQLITE_OMIT_FOREIGN_KEY */ |