Avoid trying to fetch metapage of an SPGist partitioned index.

This is necessary when spgcanreturn() is invoked on a partitioned
index, and the failure might be reachable in other scenarios as
well.  The rest of what spgGetCache() does is perfectly sensible
for a partitioned index, so we should allow it to go through.

I think the main takeaway from this is that we lack sufficient test
coverage for non-btree partitioned indexes.  Therefore, I added
simple test cases for brin and gin as well as spgist (hash and
gist AMs were covered already in indexing.sql).

Per bug #18256 from Alexander Lakhin.  Although the known test case
only fails since v16 (3c569049b), I've got no faith at all that there
aren't other ways to reach this problem; so back-patch to all
supported branches.

Discussion: https://postgr.es/m/18256-0b0e1b6e4a620f1b@postgresql.org

2 files changed, 59 insertions, 0 deletions

diff --git a/src/test/regress/expected/indexing.out b/src/test/regress/expected/indexing.out
index 368e735de24..e17879b794f 100644
--- a/src/test/regress/expected/indexing.out
+++ b/src/test/regress/expected/indexing.out
@@ -1282,6 +1282,45 @@ select tableoid::regclass, * from idxpart order by a;
 (8 rows)
 
 drop table idxpart;
+-- Test some other non-btree index types
+create table idxpart (a int, b text, c int[]) partition by range (a);
+create table idxpart1 partition of idxpart for values from (0) to (100000);
+set enable_seqscan to off;
+create index idxpart_brin on idxpart using brin(b);
+explain (costs off) select * from idxpart where b = 'abcd';
+                QUERY PLAN                 
+-------------------------------------------
+ Bitmap Heap Scan on idxpart1 idxpart
+   Recheck Cond: (b = 'abcd'::text)
+   ->  Bitmap Index Scan on idxpart1_b_idx
+         Index Cond: (b = 'abcd'::text)
+(4 rows)
+
+drop index idxpart_brin;
+create index idxpart_spgist on idxpart using spgist(b);
+explain (costs off) select * from idxpart where b = 'abcd';
+                QUERY PLAN                 
+-------------------------------------------
+ Bitmap Heap Scan on idxpart1 idxpart
+   Recheck Cond: (b = 'abcd'::text)
+   ->  Bitmap Index Scan on idxpart1_b_idx
+         Index Cond: (b = 'abcd'::text)
+(4 rows)
+
+drop index idxpart_spgist;
+create index idxpart_gin on idxpart using gin(c);
+explain (costs off) select * from idxpart where c @> array[42];
+                  QUERY PLAN                  
+----------------------------------------------
+ Bitmap Heap Scan on idxpart1 idxpart
+   Recheck Cond: (c @> '{42}'::integer[])
+   ->  Bitmap Index Scan on idxpart1_c_idx
+         Index Cond: (c @> '{42}'::integer[])
+(4 rows)
+
+drop index idxpart_gin;
+reset enable_seqscan;
+drop table idxpart;
 -- intentionally leave some objects around
 create table idxpart (a int) partition by range (a);
 create table idxpart1 partition of idxpart for values from (0) to (100);
diff --git a/src/test/regress/sql/indexing.sql b/src/test/regress/sql/indexing.sql
index 6f60d1dc0fd..a48a3177faf 100644
--- a/src/test/regress/sql/indexing.sql
+++ b/src/test/regress/sql/indexing.sql
@@ -668,6 +668,26 @@ insert into idxpart values (857142, 'six');
 select tableoid::regclass, * from idxpart order by a;
 drop table idxpart;
 
+-- Test some other non-btree index types
+create table idxpart (a int, b text, c int[]) partition by range (a);
+create table idxpart1 partition of idxpart for values from (0) to (100000);
+set enable_seqscan to off;
+
+create index idxpart_brin on idxpart using brin(b);
+explain (costs off) select * from idxpart where b = 'abcd';
+drop index idxpart_brin;
+
+create index idxpart_spgist on idxpart using spgist(b);
+explain (costs off) select * from idxpart where b = 'abcd';
+drop index idxpart_spgist;
+
+create index idxpart_gin on idxpart using gin(c);
+explain (costs off) select * from idxpart where c @> array[42];
+drop index idxpart_gin;
+
+reset enable_seqscan;
+drop table idxpart;
+
 -- intentionally leave some objects around
 create table idxpart (a int) partition by range (a);
 create table idxpart1 partition of idxpart for values from (0) to (100);