diff --git a/src/backend/catalog/heap.c b/src/backend/catalog/heap.c
index ab8a475923..6c3ff762df 100644
--- a/src/backend/catalog/heap.c
+++ b/src/backend/catalog/heap.c
@@ -125,7 +125,6 @@ static void SetRelationNumChecks(Relation rel, int numchecks);
 static Node *cookConstraint(ParseState *pstate,
 							Node *raw_constraint,
 							char *relname);
-static List *insert_ordered_unique_oid(List *list, Oid datum);
 
 
 /* ----------------------------------------------------------------
@@ -3384,57 +3383,21 @@ heap_truncate_find_FKs(List *relationIds)
 		if (!list_member_oid(relationIds, con->confrelid))
 			continue;
 
-		/* Add referencer unless already in input or result list */
+		/* Add referencer to result, unless present in input list */
 		if (!list_member_oid(relationIds, con->conrelid))
-			result = insert_ordered_unique_oid(result, con->conrelid);
+			result = lappend_oid(result, con->conrelid);
 	}
 
 	systable_endscan(fkeyScan);
 	table_close(fkeyRel, AccessShareLock);
 
+	/* Now sort and de-duplicate the result list */
+	list_sort(result, list_oid_cmp);
+	list_deduplicate_oid(result);
+
 	return result;
 }
 
-/*
- * insert_ordered_unique_oid
- *		Insert a new Oid into a sorted list of Oids, preserving ordering,
- *		and eliminating duplicates
- *
- * Building the ordered list this way is O(N^2), but with a pretty small
- * constant, so for the number of entries we expect it will probably be
- * faster than trying to apply qsort().  It seems unlikely someone would be
- * trying to truncate a table with thousands of dependent tables ...
- */
-static List *
-insert_ordered_unique_oid(List *list, Oid datum)
-{
-	ListCell   *prev;
-
-	/* Does the datum belong at the front? */
-	if (list == NIL || datum < linitial_oid(list))
-		return lcons_oid(datum, list);
-	/* Does it match the first entry? */
-	if (datum == linitial_oid(list))
-		return list;			/* duplicate, so don't insert */
-	/* No, so find the entry it belongs after */
-	prev = list_head(list);
-	for (;;)
-	{
-		ListCell   *curr = lnext(list, prev);
-
-		if (curr == NULL || datum < lfirst_oid(curr))
-			break;				/* it belongs after 'prev', before 'curr' */
-
-		if (datum == lfirst_oid(curr))
-			return list;		/* duplicate, so don't insert */
-
-		prev = curr;
-	}
-	/* Insert datum into list after 'prev' */
-	lappend_cell_oid(list, prev, datum);
-	return list;
-}
-
 /*
  * StorePartitionKey
  *		Store information about the partition key rel into the catalog
diff --git a/src/backend/nodes/list.c b/src/backend/nodes/list.c
index 279d7a91c4..0b8686d262 100644
--- a/src/backend/nodes/list.c
+++ b/src/backend/nodes/list.c
@@ -1297,6 +1297,34 @@ list_concat_unique_oid(List *list1, const List *list2)
 	return list1;
 }
 
+/*
+ * Remove adjacent duplicates in a list of OIDs.
+ *
+ * It is caller's responsibility to have sorted the list to bring duplicates
+ * together, perhaps via list_sort(list, list_oid_cmp).
+ */
+void
+list_deduplicate_oid(List *list)
+{
+	int			len;
+
+	Assert(IsOidList(list));
+	len = list_length(list);
+	if (len > 1)
+	{
+		ListCell   *elements = list->elements;
+		int			i = 0;
+
+		for (int j = 1; j < len; j++)
+		{
+			if (elements[i].oid_value != elements[j].oid_value)
+				elements[++i].oid_value = elements[j].oid_value;
+		}
+		list->length = i + 1;
+	}
+	check_list_invariants(list);
+}
+
 /*
  * Free all storage in a list, and optionally the pointed-to elements
  */
@@ -1444,3 +1472,19 @@ list_sort(List *list, list_sort_comparator cmp)
 	if (len > 1)
 		qsort(list->elements, len, sizeof(ListCell), (qsort_comparator) cmp);
 }
+
+/*
+ * list_sort comparator for sorting a list into ascending OID order.
+ */
+int
+list_oid_cmp(const ListCell *p1, const ListCell *p2)
+{
+	Oid			v1 = lfirst_oid(p1);
+	Oid			v2 = lfirst_oid(p2);
+
+	if (v1 < v2)
+		return -1;
+	if (v1 > v2)
+		return 1;
+	return 0;
+}
diff --git a/src/backend/utils/cache/relcache.c b/src/backend/utils/cache/relcache.c
index 3ca9a9f358..7aa5d7c7fa 100644
--- a/src/backend/utils/cache/relcache.c
+++ b/src/backend/utils/cache/relcache.c
@@ -285,7 +285,6 @@ static TupleDesc GetPgIndexDescriptor(void);
 static void AttrDefaultFetch(Relation relation);
 static void CheckConstraintFetch(Relation relation);
 static int	CheckConstraintCmp(const void *a, const void *b);
-static List *insert_ordered_oid(List *list, Oid datum);
 static void InitIndexAmRoutine(Relation relation);
 static void IndexSupportInitialize(oidvector *indclass,
 								   RegProcedure *indexSupport,
@@ -4387,8 +4386,8 @@ RelationGetIndexList(Relation relation)
 		if (!index->indislive)
 			continue;
 
-		/* Add index's OID to result list in the proper order */
-		result = insert_ordered_oid(result, index->indexrelid);
+		/* add index's OID to result list */
+		result = lappend_oid(result, index->indexrelid);
 
 		/*
 		 * Invalid, non-unique, non-immediate or predicate indexes aren't
@@ -4413,6 +4412,9 @@ RelationGetIndexList(Relation relation)
 
 	table_close(indrel, AccessShareLock);
 
+	/* Sort the result list into OID order, per API spec. */
+	list_sort(result, list_oid_cmp);
+
 	/* Now save a copy of the completed list in the relcache entry. */
 	oldcxt = MemoryContextSwitchTo(CacheMemoryContext);
 	oldlist = relation->rd_indexlist;
@@ -4494,13 +4496,16 @@ RelationGetStatExtList(Relation relation)
 	{
 		Oid			oid = ((Form_pg_statistic_ext) GETSTRUCT(htup))->oid;
 
-		result = insert_ordered_oid(result, oid);
+		result = lappend_oid(result, oid);
 	}
 
 	systable_endscan(indscan);
 
 	table_close(indrel, AccessShareLock);
 
+	/* Sort the result list into OID order, per API spec. */
+	list_sort(result, list_oid_cmp);
+
 	/* Now save a copy of the completed list in the relcache entry. */
 	oldcxt = MemoryContextSwitchTo(CacheMemoryContext);
 	oldlist = relation->rd_statlist;
@@ -4515,39 +4520,6 @@ RelationGetStatExtList(Relation relation)
 	return result;
 }
 
-/*
- * insert_ordered_oid
- *		Insert a new Oid into a sorted list of Oids, preserving ordering
- *
- * Building the ordered list this way is O(N^2), but with a pretty small
- * constant, so for the number of entries we expect it will probably be
- * faster than trying to apply qsort().  Most tables don't have very many
- * indexes...
- */
-static List *
-insert_ordered_oid(List *list, Oid datum)
-{
-	ListCell   *prev;
-
-	/* Does the datum belong at the front? */
-	if (list == NIL || datum < linitial_oid(list))
-		return lcons_oid(datum, list);
-	/* No, so find the entry it belongs after */
-	prev = list_head(list);
-	for (;;)
-	{
-		ListCell   *curr = lnext(list, prev);
-
-		if (curr == NULL || datum < lfirst_oid(curr))
-			break;				/* it belongs after 'prev', before 'curr' */
-
-		prev = curr;
-	}
-	/* Insert datum into list after 'prev' */
-	lappend_cell_oid(list, prev, datum);
-	return list;
-}
-
 /*
  * RelationGetPrimaryKeyIndex -- get OID of the relation's primary key index
  *
diff --git a/src/include/nodes/pg_list.h b/src/include/nodes/pg_list.h
index 6be26a2074..418f000629 100644
--- a/src/include/nodes/pg_list.h
+++ b/src/include/nodes/pg_list.h
@@ -563,6 +563,8 @@ extern List *list_concat_unique_ptr(List *list1, const List *list2);
 extern List *list_concat_unique_int(List *list1, const List *list2);
 extern List *list_concat_unique_oid(List *list1, const List *list2);
 
+extern void list_deduplicate_oid(List *list);
+
 extern void list_free(List *list);
 extern void list_free_deep(List *list);
 
@@ -573,4 +575,6 @@ extern List *list_copy_deep(const List *oldlist);
 typedef int (*list_sort_comparator) (const ListCell *a, const ListCell *b);
 extern void list_sort(List *list, list_sort_comparator cmp);
 
+extern int	list_oid_cmp(const ListCell *p1, const ListCell *p2);
+
 #endif							/* PG_LIST_H */