/*
**
** 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; 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++){
int iCol = pIdx->aiColumn[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; 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");
}
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(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; i<pFKey->nCol; i++){
int iReg = aiCol[i] + regData + 1;
sqlite3VdbeAddOp2(v, OP_IsNull, iReg, iOk);
}
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, 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; i<nCol; i++){
sqlite3VdbeAddOp2(v, OP_Copy, 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( pTab==pFKey->pFrom && nIncr==1 ){
int iJump = sqlite3VdbeCurrentAddr(v) + nCol + 1;
for(i=0; i<nCol; i++){
int iChild = aiCol[i]+1+regData;
int iParent = pIdx->aiColumn[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), P4_TRANSIENT);
sqlite3VdbeAddOp4Int(v, OP_Found, iCur, iOk, regRec, 0);
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);
sqlite3VdbeAddOp1(v, OP_Close, iCur);
}
/*
** 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:
**
** <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) */
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 ){
Column *pCol;
iCol = pIdx->aiColumn[i];
pCol = &pTab->aCol[iCol];
if( pTab->iPKey==iCol ) iCol = -1;
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 <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) && !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 */
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;
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;
int isIgnore = 0;
/* 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; i<pFKey->nCol; i++){
if( aiCol[i]==pTab->iPKey ){
aiCol[i] = -1;
}
#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].zName;
rcauth = sqlite3AuthReadCol(pParse, pTo->zName, zCol, iDb);
isIgnore = (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,isIgnore);
}
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,isIgnore);
}
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 ){
struct SrcList_item *pItem = pSrc->a;
pItem->pTab = pFKey->pFrom;
pItem->zName = pFKey->pFrom->zName;
pItem->pTab->nRef++;
pItem->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);
}
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 ){
FKey *p;
int i;
for(p=pTab->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;
locateFkeyIndex(pParse, pTab, p, &pIdx, 0);
if( pIdx ){
for(i=0; i<pIdx->nColumn; 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; i<p->nCol; 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; i<p->nCol; i++){
char *zKey = p->aCol[i].zCol;
int iKey;
for(iKey=0; iKey<pTab->nCol; 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 = 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( locateFkeyIndex(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 );
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;
}
/* Disable lookaside memory allocation */
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(sqlite3 *db, Table *pTab){
FKey *pFKey; /* Iterator variable */
FKey *pNext; /* Copy of pFKey->pNextFrom */
assert( db==0 || sqlite3SchemaMutexHeld(db, 0, pTab->pSchema) );
for(pFKey=pTab->pFKey; pFKey; pFKey=pNext){
/* Remove the FK from the fkeyHash hash table. */
if( !db || 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, sqlite3Strlen30(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 */