Ensure pg_dump_sort.c sorts null vs non-null namespace consistently.

tglsfdc · tglsfdc · commit abd04e0dd8a5 · 2018-08-07T13:13:42.000-04:00
The original coding here (which is, I believe, my fault) supposed that it didn't need to concern itself with the possibility that one object of a given type-priority has a namespace while another doesn't. But that's not reliably true anymore, if it ever was; and if it does happen then it's possible that DOTypeNameCompare returns self-inconsistent comparison results. That leads to unspecified behavior in qsort() and a resultant weird output order from pg_dump. This should end up being only a cosmetic problem, because any ordering constraints that actually matter should be enforced by the later dependency-based sort. Still, it's a bug, so back-patch. Report and fix by Jacob Champion, though I editorialized on his patch to the extent of making NULL sort after non-NULL, for consistency with our usual sorting definitions. Discussion: https://postgr.es/m/CABAq_6Hw+V-Kj7PNfD5tgOaWT_-qaYkc+SRmJkPLeUjYXLdxwQ@mail.gmail.com
diff --git a/src/bin/pg_dump/pg_dump_sort.c b/src/bin/pg_dump/pg_dump_sort.c
@@ -257,25 +257,32 @@ DOTypeNameCompare(const void *p1, const void *p2)
 	DumpableObject *obj2 = *(DumpableObject *const *) p2;
 	int			cmpval;
 
-	/* Sort by type */
+	/* Sort by type's priority */
 	cmpval = newObjectTypePriority[obj1->objType] -
 		newObjectTypePriority[obj2->objType];
 
 	if (cmpval != 0)
 		return cmpval;
 
 	/*
-	 * Sort by namespace.  Note that all objects of the same type should
-	 * either have or not have a namespace link, so we needn't be fancy about
-	 * cases where one link is null and the other not.
+	 * Sort by namespace.  Typically, all objects of the same priority would
+	 * either have or not have a namespace link, but there are exceptions.
+	 * Sort NULL namespace after non-NULL in such cases.
 	 */
-	if (obj1->namespace && obj2->namespace)
+	if (obj1->namespace)
 	{
-		cmpval = strcmp(obj1->namespace->dobj.name,
-						obj2->namespace->dobj.name);
-		if (cmpval != 0)
-			return cmpval;
+		if (obj2->namespace)
+		{
+			cmpval = strcmp(obj1->namespace->dobj.name,
+							obj2->namespace->dobj.name);
+			if (cmpval != 0)
+				return cmpval;
+		}
+		else
+			return -1;
 	}
+	else if (obj2->namespace)
+		return 1;
 
 	/* Sort by name */
 	cmpval = strcmp(obj1->name, obj2->name);
