pgstattuple: Add pgstathashindex.

Since pgstattuple v1.5 hasn't been released yet, no need for a new
extension version.  The new function exposes statistics about hash
indexes similar to what other pgstatindex functions return for other
index types.

Ashutosh Sharma, reviewed by Kuntal Ghosh.  Substantial further
revisions by me.

1 files changed, 4 insertions, 0 deletions

diff --git a/contrib/pgstattuple/sql/pgstattuple.sql b/contrib/pgstattuple/sql/pgstattuple.sql
index d22c9f1c46d..81fd5d693b4 100644
--- a/contrib/pgstattuple/sql/pgstattuple.sql
+++ b/contrib/pgstattuple/sql/pgstattuple.sql
@@ -47,3 +47,7 @@ select pg_relpages(relname) from pg_class where relname = 'test_pkey';
 create index test_ginidx on test using gin (b);
 
 select * from pgstatginindex('test_ginidx');
+
+create index test_hashidx on test using hash (b);
+
+select * from pgstathashindex('test_hashidx');