Fix EquivalenceClass code to handle volatile sort expressions in a more

predictable manner; in particular that if you say ORDER BY output-column-ref,
it will in fact sort by that specific column even if there are multiple
syntactic matches.  An example is
	SELECT random() AS a, random() AS b FROM ... ORDER BY b, a;
While the use-case for this might be a bit debatable, it worked as expected
in earlier releases, so we should preserve the behavior for 8.3.  Per my
recent proposal.

While at it, fix convert_subquery_pathkeys() to handle RelabelType stripping
in both directions; it needs this for the same reasons make_sort_from_pathkeys
does.

src/backend/nodes/outfuncs.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/nodes/outfuncs.c,v 1.315 2007/10/11 18:05:27 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/nodes/outfuncs.c,v 1.316 2007/11/08 21:49:47 tgl Exp $
  *
  * NOTES
  *	  Every node type that can appear in stored rules' parsetrees *must*
@@ -1405,6 +1405,7 @@ _outEquivalenceClass(StringInfo str, EquivalenceClass *node)
 	WRITE_BOOL_FIELD(ec_has_volatile);
 	WRITE_BOOL_FIELD(ec_below_outer_join);
 	WRITE_BOOL_FIELD(ec_broken);
+	WRITE_UINT_FIELD(ec_sortref);
 }
 
 static void

src/backend/optimizer/path/equivclass.c

@@ -10,7 +10,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/path/equivclass.c,v 1.3 2007/07/07 20:46:45 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/path/equivclass.c,v 1.4 2007/11/08 21:49:47 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -294,6 +294,7 @@ process_equivalence(PlannerInfo *root, RestrictInfo *restrictinfo,
 		ec->ec_has_volatile = false;
 		ec->ec_below_outer_join = below_outer_join;
 		ec->ec_broken = false;
+		ec->ec_sortref = 0;
 		ec->ec_merged = NULL;
 		em1 = add_eq_member(ec, item1, item1_relids, false, item1_type);
 		em2 = add_eq_member(ec, item2, item2_relids, false, item2_type);
@@ -354,6 +355,9 @@ add_eq_member(EquivalenceClass *ec, Expr *expr, Relids relids,
  *	  class it is a member of; if none, build a new single-member
  *	  EquivalenceClass for it.
  *
+ * sortref is the SortGroupRef of the originating SortClause, if any,
+ * or zero if not.
+ *
  * This can be used safely both before and after EquivalenceClass merging;
  * since it never causes merging it does not invalidate any existing ECs
  * or PathKeys.
@@ -367,7 +371,8 @@ EquivalenceClass *
 get_eclass_for_sort_expr(PlannerInfo *root,
 						 Expr *expr,
 						 Oid expr_datatype,
-						 List *opfamilies)
+						 List *opfamilies,
+						 Index sortref)
 {
 	EquivalenceClass *newec;
 	EquivalenceMember *newem;
@@ -382,7 +387,9 @@ get_eclass_for_sort_expr(PlannerInfo *root,
 		EquivalenceClass *cur_ec = (EquivalenceClass *) lfirst(lc1);
 		ListCell   *lc2;
 
-		/* we allow matching to a volatile EC here */
+		/* Never match to a volatile EC */
+		if (cur_ec->ec_has_volatile)
+			continue;
 
 		if (!equal(opfamilies, cur_ec->ec_opfamilies))
 			continue;
@@ -423,6 +430,7 @@ get_eclass_for_sort_expr(PlannerInfo *root,
 	newec->ec_has_volatile = contain_volatile_functions((Node *) expr);
 	newec->ec_below_outer_join = false;
 	newec->ec_broken = false;
+	newec->ec_sortref = sortref;
 	newec->ec_merged = NULL;
 	newem = add_eq_member(newec, expr, pull_varnos((Node *) expr),
 						  false, expr_datatype);

src/backend/optimizer/path/pathkeys.c

@@ -11,7 +11,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/path/pathkeys.c,v 1.88 2007/11/08 19:25:37 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/path/pathkeys.c,v 1.89 2007/11/08 21:49:47 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -46,6 +46,7 @@ static bool pathkey_is_redundant(PathKey *new_pathkey, List *pathkeys);
 static PathKey *make_pathkey_from_sortinfo(PlannerInfo *root,
 						   Expr *expr, Oid ordering_op,
 						   bool nulls_first,
+						   Index sortref,
 						   bool canonicalize);
 static Var *find_indexkey_var(PlannerInfo *root, RelOptInfo *rel,
 				  AttrNumber varattno);
@@ -233,6 +234,9 @@ canonicalize_pathkeys(PlannerInfo *root, List *pathkeys)
  *	  a PathKey.  If canonicalize = true, the result is a "canonical"
  *	  PathKey, otherwise not.  (But note it might be redundant anyway.)
  *
+ * If the PathKey is being generated from a SortClause, sortref should be
+ * the SortClause's SortGroupRef; otherwise zero.
+ *
  * canonicalize should always be TRUE after EquivalenceClass merging has
  * been performed, but FALSE if we haven't done EquivalenceClass merging yet.
  */
@@ -240,6 +244,7 @@ static PathKey *
 make_pathkey_from_sortinfo(PlannerInfo *root,
 						   Expr *expr, Oid ordering_op,
 						   bool nulls_first,
+						   Index sortref,
 						   bool canonicalize)
 {
 	Oid			opfamily,
@@ -303,7 +308,8 @@ make_pathkey_from_sortinfo(PlannerInfo *root,
 	}
 
 	/* Now find or create a matching EquivalenceClass */
-	eclass = get_eclass_for_sort_expr(root, expr, opcintype, opfamilies);
+	eclass = get_eclass_for_sort_expr(root, expr, opcintype, opfamilies,
+									  sortref);
 
 	/* And finally we can find or create a PathKey node */
 	if (canonicalize)
@@ -525,6 +531,7 @@ build_index_pathkeys(PlannerInfo *root,
 											  indexkey,
 											  sortop,
 											  nulls_first,
+											  0,
 											  true);
 
 		/* Add to list unless redundant */
@@ -597,41 +604,87 @@ convert_subquery_pathkeys(PlannerInfo *root, RelOptInfo *rel,
 		PathKey	   *sub_pathkey = (PathKey *) lfirst(i);
 		EquivalenceClass *sub_eclass = sub_pathkey->pk_eclass;
 		PathKey	   *best_pathkey = NULL;
+
+		if (sub_eclass->ec_has_volatile)
+		{
+			/*
+			 * If the sub_pathkey's EquivalenceClass is volatile, then it must
+			 * have come from an ORDER BY clause, and we have to match it to
+			 * that same targetlist entry.
+			 */
+			TargetEntry *tle;
+
+			if (sub_eclass->ec_sortref == 0)		/* can't happen */
+				elog(ERROR, "volatile EquivalenceClass has no sortref");
+			tle = get_sortgroupref_tle(sub_eclass->ec_sortref, sub_tlist);
+			Assert(tle);
+			/* resjunk items aren't visible to outer query */
+			if (!tle->resjunk)
+			{
+				/* We can represent this sub_pathkey */
+				EquivalenceMember *sub_member;
+				Expr	   *outer_expr;
+				EquivalenceClass *outer_ec;
+
+				Assert(list_length(sub_eclass->ec_members) == 1);
+				sub_member = (EquivalenceMember *) linitial(sub_eclass->ec_members);
+				outer_expr = (Expr *)
+					makeVar(rel->relid,
+							tle->resno,
+							exprType((Node *) tle->expr),
+							exprTypmod((Node *) tle->expr),
+							0);
+				outer_ec =
+					get_eclass_for_sort_expr(root,
+											 outer_expr,
+											 sub_member->em_datatype,
+											 sub_eclass->ec_opfamilies,
+											 0);
+				best_pathkey =
+					make_canonical_pathkey(root,
+										   outer_ec,
+										   sub_pathkey->pk_opfamily,
+										   sub_pathkey->pk_strategy,
+										   sub_pathkey->pk_nulls_first);
+			}
+		}
+		else
+		{
+			/*
+			 * Otherwise, the sub_pathkey's EquivalenceClass could contain
+			 * multiple elements (representing knowledge that multiple items
+			 * are effectively equal).  Each element might match none, one, or
+			 * more of the output columns that are visible to the outer
+			 * query. This means we may have multiple possible representations
+			 * of the sub_pathkey in the context of the outer query.  Ideally
+			 * we would generate them all and put them all into an EC of the
+			 * outer query, thereby propagating equality knowledge up to the
+			 * outer query.  Right now we cannot do so, because the outer
+			 * query's EquivalenceClasses are already frozen when this is
+			 * called. Instead we prefer the one that has the highest "score"
+			 * (number of EC peers, plus one if it matches the outer
+			 * query_pathkeys). This is the most likely to be useful in the
+			 * outer query.
+			 */
 			int			best_score = -1;
 			ListCell   *j;
 
-		/*
-		 * The sub_pathkey's EquivalenceClass could contain multiple elements
-		 * (representing knowledge that multiple items are effectively equal).
-		 * Each element might match none, one, or more of the output columns
-		 * that are visible to the outer query. This means we may have
-		 * multiple possible representations of the sub_pathkey in the context
-		 * of the outer query.  Ideally we would generate them all and put
-		 * them all into an EC of the outer query, thereby propagating
-		 * equality knowledge up to the outer query.  Right now we cannot do
-		 * so, because the outer query's EquivalenceClasses are already frozen
-		 * when this is called. Instead we prefer the one that has the highest
-		 * "score" (number of EC peers, plus one if it matches the outer
-		 * query_pathkeys). This is the most likely to be useful in the outer
-		 * query.
-		 */
 			foreach(j, sub_eclass->ec_members)
 			{
 				EquivalenceMember *sub_member = (EquivalenceMember *) lfirst(j);
 				Expr	   *sub_expr = sub_member->em_expr;
-			Expr	   *rtarg;
+				Expr	   *sub_stripped;
 				ListCell   *k;
 
 				/*
-			 * We handle two cases: the sub_pathkey key can be either an exact
+				 * We handle two cases: the sub_pathkey key can be either an
-			 * match for a targetlist entry, or a RelabelType of a targetlist
+				 * exact match for a targetlist entry, or it could match after
-			 * entry.  (The latter case is worth extra code because it arises
+				 * stripping RelabelType nodes.  (We need that case since
-			 * frequently in connection with varchar fields.)
+				 * make_pathkey_from_sortinfo could add or remove RelabelType.)
 				 */
-			if (IsA(sub_expr, RelabelType))
+				sub_stripped = sub_expr;
-				rtarg = ((RelabelType *) sub_expr)->arg;
+				while (sub_stripped && IsA(sub_stripped, RelabelType))
-			else
+					sub_stripped = ((RelabelType *) sub_stripped)->arg;
-				rtarg = NULL;
 
 				foreach(k, sub_tlist)
 				{
@@ -655,7 +708,15 @@ convert_subquery_pathkeys(PlannerInfo *root, RelOptInfo *rel,
 									exprTypmod((Node *) tle->expr),
 									0);
 					}
-				else if (rtarg && equal(tle->expr, rtarg))
+					else
+					{
+						Expr	   *tle_stripped;
+
+						tle_stripped = tle->expr;
+						while (tle_stripped && IsA(tle_stripped, RelabelType))
+							tle_stripped = ((RelabelType *) tle_stripped)->arg;
+
+						if (equal(tle_stripped, sub_stripped))
 						{
 							/* Match after discarding RelabelType */
 							outer_expr = (Expr *)
@@ -664,20 +725,24 @@ convert_subquery_pathkeys(PlannerInfo *root, RelOptInfo *rel,
 										exprType((Node *) tle->expr),
 										exprTypmod((Node *) tle->expr),
 										0);
+							if (exprType((Node *) outer_expr) !=
+								exprType((Node *) sub_expr))
 								outer_expr = (Expr *)
-						makeRelabelType((Expr *) outer_expr,
+									makeRelabelType(outer_expr,
-										((RelabelType *) sub_expr)->resulttype,
+													exprType((Node *) sub_expr),
-									 ((RelabelType *) sub_expr)->resulttypmod,
+													-1,
-								   ((RelabelType *) sub_expr)->relabelformat);
+													COERCE_DONTCARE);
 						}
 						else
 							continue;
+					}
 
 					/* Found a representation for this sub_pathkey */
 					outer_ec = get_eclass_for_sort_expr(root,
 														outer_expr,
 														sub_member->em_datatype,
-													sub_eclass->ec_opfamilies);
+														sub_eclass->ec_opfamilies,
+														0);
 					outer_pk = make_canonical_pathkey(root,
 													  outer_ec,
 													  sub_pathkey->pk_opfamily,
@@ -696,6 +761,7 @@ convert_subquery_pathkeys(PlannerInfo *root, RelOptInfo *rel,
 					}
 				}
 			}
+		}
 
 		/*
 		 * If we couldn't find a representation of this sub_pathkey, we're
@@ -795,6 +861,7 @@ make_pathkeys_for_sortclauses(PlannerInfo *root,
 											 sortkey,
 											 sortcl->sortop,
 											 sortcl->nulls_first,
+											 sortcl->tleSortGroupRef,
 											 canonicalize);
 
 		/* Canonical form eliminates redundant ordering keys */
@@ -843,12 +910,14 @@ cache_mergeclause_eclasses(PlannerInfo *root, RestrictInfo *restrictinfo)
 			get_eclass_for_sort_expr(root,
 									 (Expr *) get_leftop(clause),
 									 lefttype,
-									 restrictinfo->mergeopfamilies);
+									 restrictinfo->mergeopfamilies,
+									 0);
 		restrictinfo->right_ec =
 			get_eclass_for_sort_expr(root,
 									 (Expr *) get_rightop(clause),
 									 righttype,
-									 restrictinfo->mergeopfamilies);
+									 restrictinfo->mergeopfamilies,
+									 0);
 	}
 	else
 		Assert(restrictinfo->right_ec != NULL);

src/backend/optimizer/plan/createplan.c

@@ -10,7 +10,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/plan/createplan.c,v 1.233 2007/11/08 19:25:37 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/plan/createplan.c,v 1.234 2007/11/08 21:49:47 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -2730,27 +2730,45 @@ make_sort_from_pathkeys(PlannerInfo *root, Plan *lefttree, List *pathkeys,
 	foreach(i, pathkeys)
 	{
 		PathKey	   *pathkey = (PathKey *) lfirst(i);
+		EquivalenceClass *ec = pathkey->pk_eclass;
 		TargetEntry *tle = NULL;
 		Oid			pk_datatype = InvalidOid;
 		Oid			sortop;
 		ListCell   *j;
 
+		if (ec->ec_has_volatile)
+		{
 			/*
-		 * We can sort by any non-constant expression listed in the pathkey's
+			 * If the pathkey's EquivalenceClass is volatile, then it must
-		 * EquivalenceClass.  For now, we take the first one that corresponds
+			 * have come from an ORDER BY clause, and we have to match it to
-		 * to an available item in the tlist. If there isn't any, use the first
+			 * that same targetlist entry.
-		 * one that is an expression in the input's vars.  (The non-const
+			 */
-		 * restriction only matters if the EC is below_outer_join; but if it
+			if (ec->ec_sortref == 0)		/* can't happen */
-		 * isn't, it won't contain consts anyway, else we'd have discarded
+				elog(ERROR, "volatile EquivalenceClass has no sortref");
-		 * the pathkey as redundant.)
+			tle = get_sortgroupref_tle(ec->ec_sortref, tlist);
+			Assert(tle);
+			Assert(list_length(ec->ec_members) == 1);
+			pk_datatype = ((EquivalenceMember *) linitial(ec->ec_members))->em_datatype;
+		}
+		else
+		{
+			/*
+			 * Otherwise, we can sort by any non-constant expression listed in
+			 * the pathkey's EquivalenceClass.  For now, we take the first one
+			 * that corresponds to an available item in the tlist.  If there
+			 * isn't any, use the first one that is an expression in the
+			 * input's vars.  (The non-const restriction only matters if the
+			 * EC is below_outer_join; but if it isn't, it won't contain
+			 * consts anyway, else we'd have discarded the pathkey as
+			 * redundant.)
 			 *
 			 * XXX if we have a choice, is there any way of figuring out which
-		 * might be cheapest to execute?  (For example, int4lt is likely much
+			 * might be cheapest to execute?  (For example, int4lt is likely
-		 * cheaper to execute than numericlt, but both might appear in the
+			 * much cheaper to execute than numericlt, but both might appear
-		 * same equivalence class...)  Not clear that we ever will have an
+			 * in the same equivalence class...)  Not clear that we ever will
-		 * interesting choice in practice, so it may not matter.
+			 * have an interesting choice in practice, so it may not matter.
 			 */
-		foreach(j, pathkey->pk_eclass->ec_members)
+			foreach(j, ec->ec_members)
 			{
 				EquivalenceMember *em = (EquivalenceMember *) lfirst(j);
 
@@ -2778,12 +2796,13 @@ make_sort_from_pathkeys(PlannerInfo *root, Plan *lefttree, List *pathkeys,
 					break;			/* found expr already in tlist */
 				}
 			}
+
 			if (!tle)
 			{
 				/* No matching tlist item; look for a computable expression */
 				Expr   *sortexpr = NULL;
 
-			foreach(j, pathkey->pk_eclass->ec_members)
+				foreach(j, ec->ec_members)
 				{
 					EquivalenceMember *em = (EquivalenceMember *) lfirst(j);
 					List	   *exprvars;
@@ -2815,7 +2834,8 @@ make_sort_from_pathkeys(PlannerInfo *root, Plan *lefttree, List *pathkeys,
 				{
 					/* copy needed so we don't modify input's tlist below */
 					tlist = copyObject(tlist);
-				lefttree = (Plan *) make_result(root, tlist, NULL, lefttree);
+					lefttree = (Plan *) make_result(root, tlist, NULL,
+													lefttree);
 				}
 
 				/*
@@ -2828,6 +2848,7 @@ make_sort_from_pathkeys(PlannerInfo *root, Plan *lefttree, List *pathkeys,
 				tlist = lappend(tlist, tle);
 				lefttree->targetlist = tlist;	/* just in case NIL before */
 			}
+		}
 
 		/*
 		 * Look up the correct sort operator from the PathKey's slightly

src/backend/optimizer/util/tlist.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/util/tlist.c,v 1.75 2007/11/08 19:25:37 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/util/tlist.c,v 1.76 2007/11/08 21:49:47 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -131,6 +131,29 @@ add_to_flat_tlist(List *tlist, List *vars)
 	return tlist;
 }
 
+
+/*
+ * get_sortgroupref_tle
+ *		Find the targetlist entry matching the given SortGroupRef index,
+ *		and return it.
+ */
+TargetEntry *
+get_sortgroupref_tle(Index sortref, List *targetList)
+{
+	ListCell   *l;
+
+	foreach(l, targetList)
+	{
+		TargetEntry *tle = (TargetEntry *) lfirst(l);
+
+		if (tle->ressortgroupref == sortref)
+			return tle;
+	}
+
+	elog(ERROR, "ORDER/GROUP BY expression not found in targetlist");
+	return NULL;				/* keep compiler quiet */
+}
+
 /*
  * get_sortgroupclause_tle
  *		Find the targetlist entry matching the given SortClause
@@ -143,19 +166,7 @@ TargetEntry *
 get_sortgroupclause_tle(SortClause *sortClause,
 						List *targetList)
 {
-	Index		refnumber = sortClause->tleSortGroupRef;
+	return get_sortgroupref_tle(sortClause->tleSortGroupRef, targetList);
-	ListCell   *l;
-
-	foreach(l, targetList)
-	{
-		TargetEntry *tle = (TargetEntry *) lfirst(l);
-
-		if (tle->ressortgroupref == refnumber)
-			return tle;
-	}
-
-	elog(ERROR, "ORDER/GROUP BY expression not found in targetlist");
-	return NULL;				/* keep compiler quiet */
 }
 
 /*

src/include/nodes/relation.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/nodes/relation.h,v 1.147 2007/10/11 18:05:27 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/nodes/relation.h,v 1.148 2007/11/08 21:49:48 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -449,7 +449,10 @@ typedef struct IndexOptInfo
  * which is a case that can't arise otherwise since clauses containing
  * volatile functions are never considered mergejoinable.  We mark such
  * EquivalenceClasses specially to prevent them from being merged with
- * ordinary EquivalenceClasses.
+ * ordinary EquivalenceClasses.  Also, for volatile expressions we have
+ * to be careful to match the EquivalenceClass to the correct targetlist
+ * entry: consider SELECT random() AS a, random() AS b ... ORDER BY b,a.
+ * So we record the SortGroupRef of the originating sort clause.
  *
  * We allow equality clauses appearing below the nullable side of an outer join
  * to form EquivalenceClasses, but these have a slightly different meaning:
@@ -472,6 +475,7 @@ typedef struct EquivalenceClass
 	bool		ec_has_volatile;	/* the (sole) member is a volatile expr */
 	bool		ec_below_outer_join;	/* equivalence applies below an OJ */
 	bool		ec_broken;			/* failed to generate needed clauses? */
+	Index		ec_sortref;			/* originating sortclause label, or 0 */
 	struct EquivalenceClass *ec_merged;		/* set if merged into another EC */
 } EquivalenceClass;
 

src/include/optimizer/paths.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/optimizer/paths.h,v 1.99 2007/09/26 18:51:51 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/optimizer/paths.h,v 1.100 2007/11/08 21:49:48 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -115,7 +115,8 @@ extern void reconsider_outer_join_clauses(PlannerInfo *root);
 extern EquivalenceClass *get_eclass_for_sort_expr(PlannerInfo *root,
 						 Expr *expr,
 						 Oid expr_datatype,
-						 List *opfamilies);
+						 List *opfamilies,
+						 Index sortref);
 extern void generate_base_implied_equalities(PlannerInfo *root);
 extern List *generate_join_implied_equalities(PlannerInfo *root,
 											  RelOptInfo *joinrel,

src/include/optimizer/tlist.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/optimizer/tlist.h,v 1.46 2007/11/08 19:25:37 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/optimizer/tlist.h,v 1.47 2007/11/08 21:49:48 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -23,6 +23,8 @@ extern TargetEntry *tlist_member_ignore_relabel(Node *node, List *targetlist);
 extern List *flatten_tlist(List *tlist);
 extern List *add_to_flat_tlist(List *tlist, List *vars);
 
+extern TargetEntry *get_sortgroupref_tle(Index sortref,
+						List *targetList);
 extern TargetEntry *get_sortgroupclause_tle(SortClause *sortClause,
 						List *targetList);
 extern Node *get_sortgroupclause_expr(SortClause *sortClause,