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1474 lines (1373 loc) · 57.6 KB
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/*
**
** 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