*** ./parse_expr.c.orig	2009-02-10 22:50:47.000000000 +0100
--- ./parse_expr.c	2009-02-11 06:45:37.000000000 +0100
***************
*** 36,41 ****
--- 36,44 ----
  
  bool		Transform_null_equals = false;
  
+ /* Hook for plugins to get control in transformExpr */
+ ParseExprTransform_hook_type ParseExprTransform_hook = NULL;
+ 
  static Node *transformParamRef(ParseState *pstate, ParamRef *pref);
  static Node *transformAExprOp(ParseState *pstate, A_Expr *a);
  static Node *transformAExprAnd(ParseState *pstate, A_Expr *a);
***************
*** 97,105 ****
--- 100,118 ----
   * a Const.  More care is needed for node types that are used as both
   * input and output of transformExpr; see SubLink for example.
   */
+  
  Node *
  transformExpr(ParseState *pstate, Node *expr)
  {
+ 	if (ParseExprTransform_hook)
+ 		return (*ParseExprTransform_hook) (pstate, expr);
+ 	else
+ 		return standard_transformExpr(pstate, expr);
+ }
+  
+ Node *
+ standard_transformExpr(ParseState *pstate, Node *expr)
+ {
  	Node	   *result = NULL;
  
  	if (expr == NULL)
***************
*** 107,113 ****
  
  	/* Guard against stack overflow due to overly complex expressions */
  	check_stack_depth();
! 
  	switch (nodeTag(expr))
  	{
  		case T_ColumnRef:
--- 120,126 ----
  
  	/* Guard against stack overflow due to overly complex expressions */
  	check_stack_depth();
! 	
  	switch (nodeTag(expr))
  	{
  		case T_ColumnRef:
***************
*** 313,319 ****
  			/* should not reach here */
  			elog(ERROR, "unrecognized node type: %d", (int) nodeTag(expr));
  			break;
! 	}
  
  	return result;
  }
--- 326,332 ----
  			/* should not reach here */
  			elog(ERROR, "unrecognized node type: %d", (int) nodeTag(expr));
  			break;
! 	}	
  
  	return result;
  }