Fix handling Inf and Nan values in GiST pairing heap comparator

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
index 893d7765b6cd77208f83180ed6c8feec4a9a2c10..636aa62b680042a99c32d79afad4cd2632004ecf 100644 (file)
--- 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/float.h"
 #include "utils/lsyscache.h"
 #include "utils/memutils.h"
 #include "utils/rel.h"
@@ -36,8 +37,10 @@ pairingheap_GISTSearchItem_cmp(const pairingheap_node *a, const pairingheap_node
    /* 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;
    }
 
    /* Heap items go before inner pages, to ensure a depth-first search */

diff --git a/src/test/regress/expected/create_index.out b/src/test/regress/expected/create_index.out
index c8700f5c9c6c4d9a664f1cc3ba848e25e42ff48b..c53c802bf8660b484c034bb49dfb0f5306f98693 100644 (file)
--- a/src/test/regress/expected/create_index.out
+++ b/src/test/regress/expected/create_index.out
@@ -523,16 +523,16 @@ SELECT * FROM point_tbl ORDER BY f1 <-> '0,1';
 SELECT * FROM point_tbl ORDER BY f1 <-> '0,1';
         f1         
 -------------------
- (10,10)
- (NaN,NaN)
  (0,0)
  (1e-300,-1e-300)
  (-3,4)
  (-10,0)
+ (10,10)
  (-5,-12)
  (5.1,34.5)
- 
  (1e+300,Infinity)
+ 
+ (NaN,NaN)
 (10 rows)
 
 EXPLAIN (COSTS OFF)
@@ -561,15 +561,15 @@ SELECT * FROM point_tbl WHERE f1 IS NOT NULL ORDER BY f1 <-> '0,1';
 SELECT * FROM point_tbl WHERE f1 IS NOT NULL ORDER BY f1 <-> '0,1';
         f1         
 -------------------
- (10,10)
- (NaN,NaN)
  (0,0)
  (1e-300,-1e-300)
  (-3,4)
  (-10,0)
+ (10,10)
  (-5,-12)
  (5.1,34.5)
  (1e+300,Infinity)
+ (NaN,NaN)
 (9 rows)
 
 EXPLAIN (COSTS OFF)