Fix intarray's GiST opclasses to not fail for empty arrays with <@.

contrib/intarray considers "arraycol <@ constant-array" to be indexable,
but its GiST opclass code fails to reliably find index entries for empty
array values (which of course should trivially match such queries).
This is because the test condition to see whether we should descend
through a non-leaf node is wrong.

Unfortunately, empty array entries could be anywhere in the index,
as these index opclasses are currently designed.  So there's no way
to fix this except by lobotomizing <@ indexscans to scan the whole
index ... which is what this patch does.  That's pretty unfortunate:
the performance is now actually worse than a seqscan, in most cases.
We'd be better off to remove <@ from the GiST opclasses entirely,
and perhaps a future non-back-patchable patch will do so.

In the meantime, applications whose performance is adversely impacted
have a couple of options.  They could switch to a GIN index, which
doesn't have this bug, or they could replace "arraycol <@ constant-array"
with "arraycol <@ constant-array AND arraycol && constant-array".
That will provide about the same performance as before, and it will find
all non-empty subsets of the given constant-array, which is all that
could reliably be expected of the query before.

While at it, add some more regression test cases to improve code
coverage of contrib/intarray.

In passing, adjust resize_intArrayType so that when it's returning an
empty array, it uses construct_empty_array for that rather than
cowboy hacking on the input array.  While the hack produces an array
that looks valid for most purposes, it isn't bitwise equal to empty
arrays produced by other code paths, which could have subtle odd
effects.  I don't think this code path is performance-critical
enough to justify such shortcuts.  (Back-patch this part only as far
as v11; before commit 01783ac36 we were not careful about this in
other intarray code paths either.)

Back-patch the <@ fixes to all supported versions, since this was
broken from day one.

Patch by me; thanks to Alexander Korotkov for review.

Discussion: https://postgr.es/m/458.1565114141@sss.pgh.pa.us

diff --git a/contrib/intarray/_int_gist.c b/contrib/intarray/_int_gist.c
index b2a84a9b68b3a78d99406560c9adc1e998a96108..b2f5a3addf648d20ddeef0b2ebca8adc3ba60782 100644 (file)
--- a/contrib/intarray/_int_gist.c
+++ b/contrib/intarray/_int_gist.c
@@ -96,8 +96,13 @@ g_int_consistent(PG_FUNCTION_ARGS)
                                retval = inner_int_contains(query,
                                                                                        (ArrayType *) DatumGetPointer(entry->key));
                        else
-                               retval = inner_int_overlap((ArrayType *) DatumGetPointer(entry->key),
-                                                                                  query);
+                       {
+                               /*
+                                * Unfortunately, because empty arrays could be anywhere in
+                                * the index, we must search the whole tree.
+                                */
+                               retval = true;
+                       }
                        break;
                default:
                        retval = FALSE;

diff --git a/contrib/intarray/_intbig_gist.c b/contrib/intarray/_intbig_gist.c
index 6dae7c91c126f187374f8f2e9ef7e27b4b802368..f3c1ab764dcc07d343947ba80a8239030d93eefe 100644 (file)
--- a/contrib/intarray/_intbig_gist.c
+++ b/contrib/intarray/_intbig_gist.c
@@ -591,7 +591,13 @@ g_intbig_consistent(PG_FUNCTION_ARGS)
                                }
                        }
                        else
-                               retval = _intbig_overlap((GISTTYPE *) DatumGetPointer(entry->key), query);
+                       {
+                               /*
+                                * Unfortunately, because empty arrays could be anywhere in
+                                * the index, we must search the whole tree.
+                                */
+                               retval = true;
+                       }
                        break;
                default:
                        retval = FALSE;

diff --git a/contrib/intarray/expected/_int.out b/contrib/intarray/expected/_int.out
index 0a5dd463acb087180fa64a0d45c3bb2f39fc3d15..77f827b1f68b346efef9a1f866c433cc2435c90c 100644 (file)
--- a/contrib/intarray/expected/_int.out
+++ b/contrib/intarray/expected/_int.out
@@ -407,6 +407,18 @@ SELECT count(*) from test__int WHERE a @> '{20,23}';
     12
 (1 row)
 
+SELECT count(*) from test__int WHERE a <@ '{73,23,20}';
+ count 
+-------
+    10
+(1 row)
+
+SELECT count(*) from test__int WHERE a = '{73,23,20}';
+ count 
+-------
+     1
+(1 row)
+
 SELECT count(*) from test__int WHERE a @@ '50&68';
  count 
 -------
@@ -425,6 +437,19 @@ SELECT count(*) from test__int WHERE a @@ '(20&23)|(50&68)';
     21
 (1 row)
 
+SELECT count(*) from test__int WHERE a @@ '20 | !21';
+ count 
+-------
+  6566
+(1 row)
+
+SELECT count(*) from test__int WHERE a @@ '!20 & !21';
+ count 
+-------
+  6343
+(1 row)
+
+SET enable_seqscan = off;  -- not all of these would use index by default
 CREATE INDEX text_idx on test__int using gist ( a gist__int_ops );
 SELECT count(*) from test__int WHERE a && '{23,50}';
  count 
@@ -456,6 +481,18 @@ SELECT count(*) from test__int WHERE a @> '{20,23}';
     12
 (1 row)
 
+SELECT count(*) from test__int WHERE a <@ '{73,23,20}';
+ count 
+-------
+    10
+(1 row)
+
+SELECT count(*) from test__int WHERE a = '{73,23,20}';
+ count 
+-------
+     1
+(1 row)
+
 SELECT count(*) from test__int WHERE a @@ '50&68';
  count 
 -------
@@ -474,6 +511,18 @@ SELECT count(*) from test__int WHERE a @@ '(20&23)|(50&68)';
     21
 (1 row)
 
+SELECT count(*) from test__int WHERE a @@ '20 | !21';
+ count 
+-------
+  6566
+(1 row)
+
+SELECT count(*) from test__int WHERE a @@ '!20 & !21';
+ count 
+-------
+  6343
+(1 row)
+
 DROP INDEX text_idx;
 CREATE INDEX text_idx on test__int using gist ( a gist__intbig_ops );
 SELECT count(*) from test__int WHERE a && '{23,50}';
@@ -506,6 +555,18 @@ SELECT count(*) from test__int WHERE a @> '{20,23}';
     12
 (1 row)
 
+SELECT count(*) from test__int WHERE a <@ '{73,23,20}';
+ count 
+-------
+    10
+(1 row)
+
+SELECT count(*) from test__int WHERE a = '{73,23,20}';
+ count 
+-------
+     1
+(1 row)
+
 SELECT count(*) from test__int WHERE a @@ '50&68';
  count 
 -------
@@ -524,6 +585,18 @@ SELECT count(*) from test__int WHERE a @@ '(20&23)|(50&68)';
     21
 (1 row)
 
+SELECT count(*) from test__int WHERE a @@ '20 | !21';
+ count 
+-------
+  6566
+(1 row)
+
+SELECT count(*) from test__int WHERE a @@ '!20 & !21';
+ count 
+-------
+  6343
+(1 row)
+
 DROP INDEX text_idx;
 CREATE INDEX text_idx on test__int using gin ( a gin__int_ops );
 SELECT count(*) from test__int WHERE a && '{23,50}';
@@ -556,6 +629,18 @@ SELECT count(*) from test__int WHERE a @> '{20,23}';
     12
 (1 row)
 
+SELECT count(*) from test__int WHERE a <@ '{73,23,20}';
+ count 
+-------
+    10
+(1 row)
+
+SELECT count(*) from test__int WHERE a = '{73,23,20}';
+ count 
+-------
+     1
+(1 row)
+
 SELECT count(*) from test__int WHERE a @@ '50&68';
  count 
 -------
@@ -574,3 +659,16 @@ SELECT count(*) from test__int WHERE a @@ '(20&23)|(50&68)';
     21
 (1 row)
 
+SELECT count(*) from test__int WHERE a @@ '20 | !21';
+ count 
+-------
+  6566
+(1 row)
+
+SELECT count(*) from test__int WHERE a @@ '!20 & !21';
+ count 
+-------
+  6343
+(1 row)
+
+RESET enable_seqscan;

diff --git a/contrib/intarray/sql/_int.sql b/contrib/intarray/sql/_int.sql
index 44e1a729b4f0dbf29d8b829d0b6c96b00897457e..fd3be8f271c8fd3bed1b70d32896ade35262220c 100644 (file)
--- a/contrib/intarray/sql/_int.sql
+++ b/contrib/intarray/sql/_int.sql
@@ -81,9 +81,15 @@ SELECT count(*) from test__int WHERE a @@ '23|50';
 SELECT count(*) from test__int WHERE a @> '{23,50}';
 SELECT count(*) from test__int WHERE a @@ '23&50';
 SELECT count(*) from test__int WHERE a @> '{20,23}';
+SELECT count(*) from test__int WHERE a <@ '{73,23,20}';
+SELECT count(*) from test__int WHERE a = '{73,23,20}';
 SELECT count(*) from test__int WHERE a @@ '50&68';
 SELECT count(*) from test__int WHERE a @> '{20,23}' or a @> '{50,68}';
 SELECT count(*) from test__int WHERE a @@ '(20&23)|(50&68)';
+SELECT count(*) from test__int WHERE a @@ '20 | !21';
+SELECT count(*) from test__int WHERE a @@ '!20 & !21';
+
+SET enable_seqscan = off;  -- not all of these would use index by default
 
 CREATE INDEX text_idx on test__int using gist ( a gist__int_ops );
 
@@ -92,9 +98,13 @@ SELECT count(*) from test__int WHERE a @@ '23|50';
 SELECT count(*) from test__int WHERE a @> '{23,50}';
 SELECT count(*) from test__int WHERE a @@ '23&50';
 SELECT count(*) from test__int WHERE a @> '{20,23}';
+SELECT count(*) from test__int WHERE a <@ '{73,23,20}';
+SELECT count(*) from test__int WHERE a = '{73,23,20}';
 SELECT count(*) from test__int WHERE a @@ '50&68';
 SELECT count(*) from test__int WHERE a @> '{20,23}' or a @> '{50,68}';
 SELECT count(*) from test__int WHERE a @@ '(20&23)|(50&68)';
+SELECT count(*) from test__int WHERE a @@ '20 | !21';
+SELECT count(*) from test__int WHERE a @@ '!20 & !21';
 
 DROP INDEX text_idx;
 CREATE INDEX text_idx on test__int using gist ( a gist__intbig_ops );
@@ -104,9 +114,13 @@ SELECT count(*) from test__int WHERE a @@ '23|50';
 SELECT count(*) from test__int WHERE a @> '{23,50}';
 SELECT count(*) from test__int WHERE a @@ '23&50';
 SELECT count(*) from test__int WHERE a @> '{20,23}';
+SELECT count(*) from test__int WHERE a <@ '{73,23,20}';
+SELECT count(*) from test__int WHERE a = '{73,23,20}';
 SELECT count(*) from test__int WHERE a @@ '50&68';
 SELECT count(*) from test__int WHERE a @> '{20,23}' or a @> '{50,68}';
 SELECT count(*) from test__int WHERE a @@ '(20&23)|(50&68)';
+SELECT count(*) from test__int WHERE a @@ '20 | !21';
+SELECT count(*) from test__int WHERE a @@ '!20 & !21';
 
 DROP INDEX text_idx;
 CREATE INDEX text_idx on test__int using gin ( a gin__int_ops );
@@ -116,6 +130,12 @@ SELECT count(*) from test__int WHERE a @@ '23|50';
 SELECT count(*) from test__int WHERE a @> '{23,50}';
 SELECT count(*) from test__int WHERE a @@ '23&50';
 SELECT count(*) from test__int WHERE a @> '{20,23}';
+SELECT count(*) from test__int WHERE a <@ '{73,23,20}';
+SELECT count(*) from test__int WHERE a = '{73,23,20}';
 SELECT count(*) from test__int WHERE a @@ '50&68';
 SELECT count(*) from test__int WHERE a @> '{20,23}' or a @> '{50,68}';
 SELECT count(*) from test__int WHERE a @@ '(20&23)|(50&68)';
+SELECT count(*) from test__int WHERE a @@ '20 | !21';
+SELECT count(*) from test__int WHERE a @@ '!20 & !21';
+
+RESET enable_seqscan;