SQLite

        }
        if( i==nCol ) break;      /* pIdx is usable */
      }
    }
  }

  if( pParse && !pIdx ){
    if( !pParse->disableTriggers ){
      sqlite3ErrorMsg(pParse, "foreign key mismatch");
    }
    sqlite3DbFree(pParse->db, aiCol);
    return 1;
  }

  *ppIdx = pIdx;
  return 0;
}

  int regNew                      /* New row data is stored here */
){
  sqlite3 *db = pParse->db;       /* Database handle */
  Vdbe *v;                        /* VM to write code to */
  FKey *pFKey;                    /* Used to iterate through FKs */
  int iDb;                        /* Index of database containing pTab */
  const char *zDb;                /* Name of database containing pTab */
  int isIgnoreErrors = pParse->disableTriggers;

  assert( ( pChanges &&  (regOld==0)!=(regNew==0))    /* UPDATE operation */
       || (!pChanges && !regOld &&  regNew)           /* INSERT operation */
       || (!pChanges &&  regOld && !regNew)           /* DELETE operation */
  );

  /* If foreign-keys are disabled, this function is a no-op. */

    int iCol;
    int i;

    /* Find the parent table of this foreign key. Also find a unique index 
    ** on the parent key columns in the parent table. If either of these 
    ** schema items cannot be located, set an error in pParse and return 
    ** early.  */
    if( pParse->disableTriggers ){
      pTo = sqlite3FindTable(db, pFKey->zTo, zDb);
    }else{
      pTo = sqlite3LocateTable(pParse, 0, pFKey->zTo, zDb);
    }
    if( !pTo || locateFkeyIndex(pParse, pTo, pFKey, &pIdx, &aiFree) ){
      if( !isIgnoreErrors || db->mallocFailed ) return;
      continue;
    }
    assert( pFKey->nCol==1 || (aiFree && pIdx) );

    /* If the key does not overlap with the pChanges list, skip this FK. */
    if( pChanges ){
      /* TODO */
    }

    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 );

    /* Check if this update statement has modified any of the child key 
    ** columns for this foreign key constraint. If it has not, there is 
    ** no need to search the child table for rows in violation. This is
    ** just an optimization. Things would work fine without this check.  */
    if( pChanges ){

    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;
}

    execsql "DROP TABLE $t"
  }
  execsql { PRAGMA foreign_keys = ON }
}

execsql { PRAGMA foreign_keys = on }













set FkeySimpleSchema {
  PRAGMA foreign_keys = on;
  CREATE TABLE t1(a PRIMARY KEY, b);
  CREATE TABLE t2(c REFERENCES t1(a) /D/ , d);

  CREATE TABLE t3(a PRIMARY KEY, b);
  CREATE TABLE t4(c REFERENCES t3 /D/, d);

} {1 {foreign key constraint failed}}
do_test fkey2-14.2.2.6 {
  catchsql { UPDATE t4 SET b = 1 }
} {0 {}}
do_test fkey2-14.2.2.7 {
  execsql { INSERT INTO t3 VALUES(1, NULL, 1) }
} {}

do_test fkey-2.14.3.1 {
  drop_all_tables
  execsql {
    CREATE TABLE t1(a, b REFERENCES nosuchtable);
    DROP TABLE t1;
  }
} {}
do_test fkey-2.14.3.2 {
  execsql {
    CREATE TABLE t1(a PRIMARY KEY, b);
    INSERT INTO t1 VALUES('a', 1);
    CREATE TABLE t2(x REFERENCES t1);
    INSERT INTO t2 VALUES('a');
  }
} {}
do_test fkey-2.14.3.3 {
  catchsql { DROP TABLE t1 }
} {1 {foreign key constraint failed}}
do_test fkey-2.14.3.4 {
  execsql {
    DELETE FROM t2;
    DROP TABLE t1;
  }
} {}
do_test fkey-2.14.3.4 {
  catchsql { INSERT INTO t2 VALUES('x') }
} {1 {no such table: main.t1}}
do_test fkey-2.14.3.5 {
  execsql {
    CREATE TABLE t1(x PRIMARY KEY);
    INSERT INTO t1 VALUES('x');
  }
  execsql { INSERT INTO t2 VALUES('x') }
} {}
do_test fkey-2.14.3.6 {
  catchsql { DROP TABLE t1 }
} {1 {foreign key constraint failed}}
do_test fkey-2.14.3.7 {
  execsql {
    DROP TABLE t2;
    DROP TABLE t1;
  }
} {}
do_test fkey-2.14.3.8 {
  execsql {
    CREATE TABLE pp(x, y, PRIMARY KEY(x, y));
    CREATE TABLE cc(a, b, FOREIGN KEY(a, b) REFERENCES pp(x, z));
  }
  catchsql { INSERT INTO cc VALUES(1, 2) }
} {1 {foreign key mismatch}}
do_test fkey-2.14.3.9 {
  execsql { DROP TABLE cc }
} {}

#-------------------------------------------------------------------------
# The following tests, fkey2-15.*, test that unnecessary FK related scans 
# and lookups are avoided when the constraint counters are zero.
#
drop_all_tables
proc execsqlS {zSql} {