Cannot drop a column from a reference table on the coordinator

[marcocitus]

The checks for reference + local table joins might be too aggressive as they can show up in the drop trigger.

SELECT master_add_node('localhost', 5432, groupid := 0);
CREATE TABLE ref (a int, b int);
SELECT create_reference_table('ref');
ALTER TABLE ref DROP COLUMN z;
ERROR:  cannot join local tables and reference tables in a transaction block
CONTEXT:  while executing command on 127.0.0.1:5432
SQL statement "SELECT master_unmark_object_distributed(v_obj.classid, v_obj.objid, v_obj.objsubid)"
PL/pgSQL function citus_drop_trigger() line 28 at PERFORM

SELECT worker_apply_shard_ddl_command (102040, 'public', 'ALTER TABLE ref DROP COLUMN z;');
ERROR:  cannot join local tables and reference tables in a transaction block
CONTEXT:  SQL statement "SELECT master_unmark_object_distributed(v_obj.classid, v_obj.objid, v_obj.objsubid)"
PL/pgSQL function citus_drop_trigger() line 28 at PERFORM