SELECT pg_stat_database.datname, 
       pg_stat_database.blks_read,
       pg_stat_database.blks_hit, 
       round((pg_stat_database.blks_hit::double precision 
              / (pg_stat_database.blks_read 
                 + pg_stat_database.blks_hit 
                 +1)::double precision * 100::double precision)::numeric, 2) AS cachehitratio
   FROM pg_stat_database
  WHERE pg_stat_database.datname !~ '^(template(0|1)|postgres)$'::text
  ORDER BY round((pg_stat_database.blks_hit::double precision 
                 / (pg_stat_database.blks_read 
                    + pg_stat_database.blks_hit 
                    + 1)::double precision * 100::double precision)::numeric, 2) DESC;