QUERY PLAN                                 
----------------------------------------------------------------------------
 Hash Join  (cost=xxx rows=620 width=406)
   Hash Cond: (t1.oid = t2.oid)
   ->  Seq Scan on pg_class t1  (cost=xxx rows=620 width=207)
   ->  Hash  (cost=xxx rows=620 width=207)
         ->  Seq Scan on pg_class t2  (cost=xxx rows=620 width=207)
(5 rows)

                                 QUERY PLAN                                 
----------------------------------------------------------------------------
 Hash Join  (cost=xxx rows=1 width=406)
   Hash Cond: (t1.oid = t2.oid)
   ->  Seq Scan on pg_class t1  (cost=xxx rows=620 width=207)
   ->  Hash  (cost=xxx rows=620 width=207)
         ->  Seq Scan on pg_class t2  (cost=xxx rows=620 width=207)
(5 rows)