Adds the necessary regress tests

src/test/regress/expected/multi_cluster_management.out

@@ -25,6 +25,15 @@ SELECT citus_is_coordinator();
  t
 (1 row)
 
+-- I am primary node (fails beacuse not set in pg_dist)
+select citus_is_primary_node();
+WARNING:  could not find the current node in pg_dist_node
+DETAIL:  If this is the coordinator node, consider adding it into the metadata by using citus_set_coordinator_host() UDF. Otherwise, if you're going to use this node as a worker node for a new cluster, make sure to add this node into the metadata from the coordinator by using citus_add_node() UDF.
+ citus_is_primary_node
+---------------------------------------------------------------------
+
+(1 row)
+
 -- make sure coordinator is always in metadata.
 SELECT citus_set_coordinator_host('localhost');
  citus_set_coordinator_host
@@ -32,6 +41,13 @@ SELECT citus_set_coordinator_host('localhost');
 
 (1 row)
 
+-- I am primary node
+select citus_is_primary_node();
+ citus_is_primary_node
+---------------------------------------------------------------------
+ t
+(1 row)
+
 -- workers are not coordinator
 SELECT result FROM run_command_on_workers('SELECT citus_is_coordinator()');
  result
@@ -40,6 +56,14 @@ SELECT result FROM run_command_on_workers('SELECT citus_is_coordinator()');
  f
 (2 rows)
 
+-- primary workers are primary node
+SELECT result FROM run_command_on_workers('SELECT citus_is_primary_node()');
+ result
+---------------------------------------------------------------------
+ t
+ t
+(2 rows)
+
 -- get the active nodes
 SELECT master_get_active_worker_nodes();
  master_get_active_worker_nodes

src/test/regress/sql/multi_cluster_management.sql

@@ -14,12 +14,18 @@ RESET citus.metadata_sync_mode;
 -- I am coordinator
 SELECT citus_is_coordinator();
 
+-- I am primary node
+select citus.citus_is_primary_node();
+
 -- make sure coordinator is always in metadata.
 SELECT citus_set_coordinator_host('localhost');
 
 -- workers are not coordinator
 SELECT result FROM run_command_on_workers('SELECT citus_is_coordinator()');
 
+-- primary workers are primary node
+SELECT result FROM run_command_on_workers('SELECT citus_is_primary_node()');
+
 -- get the active nodes
 SELECT master_get_active_worker_nodes();