SELECT * FROM pg_stat_activity;

QUERY PLAN
-------------------------------------------------------------------------------
 Update on foo_table  (cost=0.00..1271.14 rows=1 width=55)
   ->  Seq Scan on foo_table  (cost=0.00..1271.14 rows=1 width=55)
         Filter: (id = 2::bigint)
(3 rows)

SELECT relname, idx_tup_fetch + seq_tup_read as TotalReads from pg_stat_all_tables WHERE idx_tup_fetch + seq_tup_read != 0 order by TotalReads;

SELECT * FROM pg_stat_all_tables ORDER BY seq_scan DESC;