SQLite

#endif
#ifdef pTrigger
 #undef pTrigger
#endif
#ifdef tmask
 #undef tmask
#endif

/* This is the Walker callback from checkConstraintUnchanged().  Set
** pWalker->eCode to 0 if this expression node references any of the
** columns that are being modifed by an UPDATE statement.
*/
static int checkConstraintExprNode(Walker *pWalker, Expr *pExpr){
  if( pExpr->op==TK_COLUMN
   && pExpr->iColumn>=0
   && pWalker->u.aiCol[pExpr->iColumn]>=0
  ){
    pWalker->eCode = 0;
  }
  return WRC_Continue;
}

/*
** pExpr is a CHECK constraint on a row that is being UPDATE-ed.  The
** only columns that are modified by the UPDATE are those for which
** aiChng[i]>=0.  Return true if CHECK constraint pExpr does not use
** any of the changing columns.  In other words, return true if this
** CHECK constraint can be skipped when validating the new row in
** the UPDATE statement.
*/
static int checkConstraintUnchanged(Expr *pExpr, int *aiChng){
  Walker w;
  memset(&w, 0, sizeof(w));
  w.eCode = 1;
  w.xExprCallback = checkConstraintExprNode;
  w.u.aiCol = aiChng;
  sqlite3WalkExpr(&w, pExpr);
  return w.eCode;
}

/*
** Generate code to do constraint checks prior to an INSERT or an UPDATE
** on table pTab.
**
** The regNewData parameter is the first register in a range that contains
** the data to be inserted or the data after the update.  There will be

#ifndef SQLITE_OMIT_CHECK
  if( pTab->pCheck && (db->flags & SQLITE_IgnoreChecks)==0 ){
    ExprList *pCheck = pTab->pCheck;
    pParse->ckBase = regNewData+1;
    onError = overrideError!=OE_Default ? overrideError : OE_Abort;
    for(i=0; i<pCheck->nExpr; i++){
      int allOk = sqlite3VdbeMakeLabel(v);
      Expr *pExpr = pCheck->a[i].pExpr;
      if( aiChng && checkConstraintUnchanged(pExpr, aiChng) ) continue;
      sqlite3ExprIfTrue(pParse, pExpr, allOk, SQLITE_JUMPIFNULL);
      if( onError==OE_Ignore ){
        sqlite3VdbeGoto(v, ignoreDest);
      }else{
        char *zName = pCheck->a[i].zName;
        if( zName==0 ) zName = pTab->zName;
        if( onError==OE_Replace ) onError = OE_Abort; /* IMP: R-15569-63625 */
        sqlite3HaltConstraint(pParse, SQLITE_CONSTRAINT_CHECK,

  union {                                   /* Extra data for callback */
    NameContext *pNC;                          /* Naming context */
    int n;                                     /* A counter */
    int iCur;                                  /* A cursor number */
    SrcList *pSrcList;                         /* FROM clause */
    struct SrcCount *pSrcCount;                /* Counting column references */
    struct CCurHint *pCCurHint;                /* Used by codeCursorHint() */
    int *aiCol;                                /* array of column indexes */
  } u;
};

/* Forward declarations */
int sqlite3WalkExpr(Walker*, Expr*);
int sqlite3WalkExprList(Walker*, ExprList*);
int sqlite3WalkSelect(Walker*, Select*);