Check activate snapshot consistency between nodes in check_mx

src/test/regress/expected/check_mx.out

@@ -10,3 +10,29 @@ SELECT bool_and(metadatasynced) FROM pg_dist_node WHERE noderole = 'primary';
  t
 (1 row)
 
+-- Create the necessary test utility function
+CREATE OR REPLACE FUNCTION activate_node_snapshot()
+    RETURNS text[]
+    LANGUAGE C STRICT
+    AS 'citus';
+-- Following tests capture the difference between the metadata in the worker nodes and the
+-- coordinator. It is expected to see no rows. However if the tests fail, we list the
+-- problematic queries in the activate_node_snapshot() result set.
+-- list all metadata that is missing in the worker nodes
+SELECT unnest(activate_node_snapshot())
+    EXCEPT
+SELECT unnest(result::text[]) AS unnested_result
+FROM run_command_on_workers($$SELECT activate_node_snapshot()$$);
+                                                                                                                                                                                                                                                                                   unnest
+---------------------------------------------------------------------
+(0 rows)
+
+-- list all the metadata that is missing on the coordinator
+SELECT unnest(result::text[]) AS unnested_result
+FROM run_command_on_workers($$SELECT activate_node_snapshot()$$)
+    EXCEPT
+SELECT unnest(activate_node_snapshot());
+                                                                                                                                                                                                                                                                        unnested_result
+---------------------------------------------------------------------
+(0 rows)
+

src/test/regress/sql/check_mx.sql

@@ -1,3 +1,25 @@
 SHOW citus.enable_metadata_sync;
 
 SELECT bool_and(metadatasynced) FROM pg_dist_node WHERE noderole = 'primary';
+
+-- Create the necessary test utility function
+CREATE OR REPLACE FUNCTION activate_node_snapshot()
+    RETURNS text[]
+    LANGUAGE C STRICT
+    AS 'citus';
+
+-- Following tests capture the difference between the metadata in the worker nodes and the
+-- coordinator. It is expected to see no rows. However if the tests fail, we list the
+-- problematic queries in the activate_node_snapshot() result set.
+
+-- list all metadata that is missing in the worker nodes
+SELECT unnest(activate_node_snapshot())
+    EXCEPT
+SELECT unnest(result::text[]) AS unnested_result
+FROM run_command_on_workers($$SELECT activate_node_snapshot()$$);
+
+-- list all the metadata that is missing on the coordinator
+SELECT unnest(result::text[]) AS unnested_result
+FROM run_command_on_workers($$SELECT activate_node_snapshot()$$)
+    EXCEPT
+SELECT unnest(activate_node_snapshot());