Add alternate expected output for pg_buffercache with 4-node cluster

The existing expected output assumes a 2-node cluster. CI uses a
standard demo cluster with 1 coordinator + 3 primaries (4 nodes),
producing 4 rows from gp_buffercache_summary and a different buffer
count match result. Add pg_buffercache_1.out for this configuration.

Author: lss602726449

contrib/pg_buffercache/expected/pg_buffercache_1.out

@@ -0,0 +1,173 @@
+CREATE EXTENSION pg_buffercache;
+select count(*) = (select setting::bigint
+                   from pg_settings
+                   where name = 'shared_buffers')
+from pg_buffercache;
+ ?column?
+----------
+ t
+(1 row)
+
+select buffers_used + buffers_unused > 0,
+        buffers_dirty <= buffers_used,
+        buffers_pinned <= buffers_used
+from pg_buffercache_summary();
+ ?column? | ?column? | ?column?
+----------+----------+----------
+ t        | t        | t
+(1 row)
+
+SELECT count(*) > 0 FROM pg_buffercache_usage_counts() WHERE buffers >= 0;
+ ?column?
+----------
+ t
+(1 row)
+
+-- Check that the functions / views can't be accessed by default. To avoid
+-- having to create a dedicated user, use the pg_database_owner pseudo-role.
+SET ROLE pg_database_owner;
+SELECT * FROM pg_buffercache;
+ERROR:  permission denied for view pg_buffercache
+SELECT * FROM pg_buffercache_pages() AS p (wrong int);
+ERROR:  permission denied for function pg_buffercache_pages
+SELECT * FROM pg_buffercache_summary();
+ERROR:  permission denied for function pg_buffercache_summary
+SELECT * FROM pg_buffercache_usage_counts();
+ERROR:  permission denied for function pg_buffercache_usage_counts
+RESET role;
+SELECT count(*) > 0 FROM pg_buffercache_usage_counts() WHERE buffers >= 0;
+ ?column?
+----------
+ t
+(1 row)
+
+-- Test GPDB functions/views
+SELECT count(*) = (select setting::bigint
+                   from pg_settings
+                   where name = 'shared_buffers') *
+                   (select count(*) from gp_segment_configuration where role='p')
+                   as buffers
+FROM gp_buffercache;
+ buffers
+---------
+ t
+(1 row)
+
+SELECT buffers_used + buffers_unused > 0,
+        buffers_dirty <= buffers_used,
+        buffers_pinned <= buffers_used
+FROM gp_buffercache_summary;
+ ?column? | ?column? | ?column?
+----------+----------+----------
+ t        | t        | t
+ t        | t        | t
+ t        | t        | t
+ t        | t        | t
+(4 rows)
+
+SELECT buffers_used + buffers_unused > 0,
+        buffers_dirty <= buffers_used,
+        buffers_pinned <= buffers_used
+FROM gp_buffercache_summary_aggregated;
+ ?column? | ?column? | ?column?
+----------+----------+----------
+ t        | t        | t
+(1 row)
+
+SELECT count(*) > 0 FROM gp_buffercache_usage_counts WHERE buffers >= 0;
+ ?column?
+----------
+ t
+(1 row)
+
+SELECT count(*) > 0 FROM gp_buffercache_usage_counts_aggregated WHERE buffers >= 0;
+ ?column?
+----------
+ t
+(1 row)
+
+-- Check that the functions / views can't be accessed by default.
+SET ROLE pg_database_owner;
+-- GPDB
+SELECT * FROM pg_buffercache_summary;
+ERROR:  permission denied for view pg_buffercache_summary
+SELECT * FROM pg_buffercache_usage_counts;
+ERROR:  permission denied for view pg_buffercache_usage_counts
+SELECT * FROM gp_buffercache;
+ERROR:  permission denied for view gp_buffercache
+SELECT * FROM gp_buffercache_summary;
+ERROR:  permission denied for view gp_buffercache_summary
+SELECT * FROM gp_buffercache_usage_counts;
+ERROR:  permission denied for view gp_buffercache_usage_counts
+SELECT * FROM gp_buffercache_summary_aggregated;
+ERROR:  permission denied for view gp_buffercache_summary_aggregated
+SELECT * FROM gp_buffercache_usage_counts_aggregated;
+ERROR:  permission denied for view gp_buffercache_usage_counts_aggregated
+RESET ROLE;
+-- Check that pg_monitor is allowed to query view / function
+SET ROLE pg_monitor;
+SELECT count(*) > 0 FROM pg_buffercache;
+ ?column?
+----------
+ t
+(1 row)
+
+SELECT buffers_used + buffers_unused > 0 FROM pg_buffercache_summary();
+ ?column?
+----------
+ t
+(1 row)
+
+SELECT count(*) > 0 FROM pg_buffercache_usage_counts();
+ ?column?
+----------
+ t
+(1 row)
+
+-- GPDB
+SELECT count(*) > 0 FROM pg_buffercache_summary;
+ ?column?
+----------
+ t
+(1 row)
+
+SELECT count(*) > 0 FROM pg_buffercache_usage_counts;
+ ?column?
+----------
+ t
+(1 row)
+
+SELECT count(*) > 0 FROM gp_buffercache;
+ ?column?
+----------
+ t
+(1 row)
+
+SELECT buffers_used + buffers_unused > 0 FROM gp_buffercache_summary;
+ ?column?
+----------
+ t
+ t
+ t
+ t
+(4 rows)
+
+SELECT buffers_used + buffers_unused > 0 FROM gp_buffercache_summary_aggregated;
+ ?column?
+----------
+ t
+(1 row)
+
+SELECT count(*) > 0 FROM gp_buffercache_usage_counts;
+ ?column?
+----------
+ t
+(1 row)
+
+SELECT count(*) > 0 FROM gp_buffercache_usage_counts_aggregated;
+ ?column?
+----------
+ t
+(1 row)
+
+RESET ROLE;