PostgreSQL　テーブルキャッシュヒット率を調べる

select
  *
from
  (
select
  io_ut.relname,
  ut.seq_scan,
  ut.seq_tup_read,
  case
    when ut.seq_scan > 0 then ut.seq_tup_read / ut.seq_scan
    else null
  end as tup_per_read,
  ut.n_live_tup,
  case
    when io_ut.heap_blks_read > 0 then round(io_ut.heap_blks_hit * 100 / (io_ut.heap_blks_hit + io_ut.heap_blks_read), 2)
    else null
  end as cache_hit_ratio
from
  pg_statio_user_tables io_ut
    left join pg_stat_user_tables ut on io_ut.relname = ut.relname
  ) h
order by
  seq_scan desc
;