I started adding the Having Clause and it works quite fine for

sequential scans! (I think it will also work with hash, index, etc
but I did not check it out! I made some High level changes which
should work for all access methods, but maybe I'm wrong. Please
let me know.)

Now it is possible to make queries like:

select s.sname, max(p.pid), min(p.pid) from part p, supplier s
where s.sid=p.sid group by s.sname having max(pid)=6 and min(pid)=1
or avg(pid)=4;

Having does not work yet for queries that contain a subselect
statement in the Having clause, I'll try to fix this in the next
days.

If there are some bugs, please let me know, I'll start to read the
mailinglists now!

Now here is the patch against the original 6.3 version (no snapshot!!):

Stefan

src/backend/optimizer/plan/planner.c

@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/optimizer/plan/planner.c,v 1.23 1998/02/26 04:32:51 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/optimizer/plan/planner.c,v 1.24 1998/03/30 16:36:04 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -59,6 +59,115 @@ make_groupPlan(List **tlist, bool tuplePerGroup,
  *
  *****************************************************************************/
 
+
+/***S*H***/ /* Anfang */
+
+static List *
+check_having_qual_for_aggs(Node *clause, List *subplanTargetList)
+{
+	List	   *t;
+	List	   *agg_list = NIL;
+
+	if (IsA(clause, Var))
+	{
+	  TargetEntry *subplanVar;
+	  
+	  /*
+	   * Ha! A Var node!
+	   */
+	  subplanVar = match_varid((Var *) clause, subplanTargetList);
+	  
+	  /*
+	   * Change the varno & varattno fields of the var node.
+	   *
+	   */
+	  ((Var *) clause)->varattno = subplanVar->resdom->resno;
+	  return NIL;
+	}
+        /***S*H***/
+	else if (is_funcclause(clause) || not_clause(clause) || 
+		 or_clause(clause) || and_clause(clause))
+	{
+
+		/*
+		 * This is a function. Recursively call this routine for its
+		 * arguments...
+		 */
+		foreach(t, ((Expr *) clause)->args)
+		{
+			agg_list = nconc(agg_list,
+					   check_having_qual_for_aggs(lfirst(t), subplanTargetList));
+		}
+		return agg_list;
+	}
+	else if (IsA(clause, Aggreg))
+	{
+		return lcons(clause,
+		    check_having_qual_for_aggs(((Aggreg *) clause)->target, subplanTargetList));
+		
+	}
+	else if (IsA(clause, ArrayRef))
+	{
+		ArrayRef   *aref = (ArrayRef *) clause;
+
+		/*
+		 * This is an arrayref. Recursively call this routine for its
+		 * expression and its index expression...
+		 */
+		foreach(t, aref->refupperindexpr)
+		{
+			agg_list = nconc(agg_list,
+					 check_having_qual_for_aggs(lfirst(t), subplanTargetList));
+		}
+		foreach(t, aref->reflowerindexpr)
+		{
+			agg_list = nconc(agg_list,
+					 check_having_qual_for_aggs(lfirst(t), subplanTargetList));
+		}
+		agg_list = nconc(agg_list,
+				 check_having_qual_for_aggs(aref->refexpr, subplanTargetList));
+		agg_list = nconc(agg_list,
+				 check_having_qual_for_aggs(aref->refassgnexpr, subplanTargetList));
+
+		return agg_list;
+	}
+	else if (is_opclause(clause))
+	{
+
+		/*
+		 * This is an operator. Recursively call this routine for both its
+		 * left and right operands
+		 */
+		Node	   *left = (Node *) get_leftop((Expr *) clause);
+		Node	   *right = (Node *) get_rightop((Expr *) clause);
+
+		if (left != (Node *) NULL)
+			agg_list = nconc(agg_list,
+					 check_having_qual_for_aggs(left, subplanTargetList));
+		if (right != (Node *) NULL)
+			agg_list = nconc(agg_list,
+					 check_having_qual_for_aggs(right, subplanTargetList));
+
+		return agg_list;
+	}
+	else if (IsA(clause, Param) ||IsA(clause, Const))
+	{
+		/* do nothing! */
+		return NIL;
+	}
+	else
+	{
+
+		/*
+		 * Ooops! we can not handle that!
+		 */
+		elog(ERROR, "check_having_qual_for_aggs: Can not handle this having_qual!\n");
+		return NIL;
+	}
+}
+/***S*H***/ /* Ende */
+
+
 Plan *
 planner(Query *parse)
 {
@@ -181,7 +290,22 @@ union_planner(Query *parse)
 		 * the result tuple of the subplans.
 		 */
 		((Agg *) result_plan)->aggs =
-			set_agg_tlist_references((Agg *) result_plan);
+			set_agg_tlist_references((Agg *) result_plan); 
+
+		/***S*H***/
+		if(parse->havingQual!=NULL) {
+		  List	   *clause;
+
+		  /***S*H***/ /* set qpqual of having clause */
+		  ((Agg *) result_plan)->plan.qual=cnfify((Expr *)parse->havingQual,true);
+
+		  foreach(clause, ((Agg *) result_plan)->plan.qual)
+		    {
+		      ((Agg *) result_plan)->aggs = nconc(((Agg *) result_plan)->aggs,
+			 check_having_qual_for_aggs((Node *) lfirst(clause),
+				       ((Agg *) result_plan)->plan.lefttree->targetlist));
+		    }
+		}
 	}
 
 	/*
@@ -429,3 +553,6 @@ pg_checkretval(Oid rettype, QueryTreeList *queryTreeList)
 	/* success */
 	return;
 }
+
+
+

src/backend/optimizer/plan/setrefs.c

@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/optimizer/plan/setrefs.c,v 1.19 1998/02/26 04:32:53 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/optimizer/plan/setrefs.c,v 1.20 1998/03/30 16:36:14 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -839,6 +839,7 @@ replace_agg_clause(Node *clause, List *subplanTargetList)
 	}
 }
 
+
 /*
  * del_agg_tlist_references
  *	  Remove the Agg nodes from the target list