Fix handling Inf and Nan values in GiST pairing heap comparator

akorotkov · akorotkov · commit 111fb7e42e33 · 2019-09-08T21:58:17.000+03:00
Previously plain float comparison was used in GiST pairing heap. Such comparison doesn't provide proper ordering for value sets containing Inf and Nan values. This commit fixes that by usage of float8_cmp_internal(). Note, there is remaining problem with NULL distances, which are represented as Inf in pairing heap. It would be fixes in subsequent commit. Backpatch to all supported versions. Reported-by: Andrey Borodin Discussion: https://postgr.es/m/CAPpHfdsNvNdA0DBS%2BwMpFrgwT6C3-q50sFVGLSiuWnV3FqOJuQ%40mail.gmail.com Author: Alexander Korotkov Reviewed-by: Heikki Linnakangas Backpatch-through: 9.4
diff --git a/src/backend/access/gist/gistscan.c b/src/backend/access/gist/gistscan.c
@@ -17,6 +17,7 @@
 #include "access/gist_private.h"
 #include "access/gistscan.h"
 #include "access/relscan.h"
+#include "utils/builtins.h"
 #include "utils/memutils.h"
 #include "utils/rel.h"
 
@@ -36,8 +37,10 @@ GISTSearchTreeItemComparator(const RBNode *a, const RBNode *b, void *arg)
 	/* Order according to distance comparison */
 	for (i = 0; i < scan->numberOfOrderBys; i++)
 	{
-		if (sa->distances[i] != sb->distances[i])
-			return (sa->distances[i] > sb->distances[i]) ? 1 : -1;
+		int			cmp = float8_cmp_internal(sa->distances[i], sb->distances[i]);
+
+		if (cmp != 0)
+			return cmp;
 	}
 
 	return 0;
