/* Calculates your cache hit rate for reading tables */

SELECT

relname AS name,
heap_blks_hit AS buffer_hits,
heap_blks_read AS block_reads,
heap_blks_hit + heap_blks_read AS total_read,
CASE (heap_blks_hit + heap_blks_read)::float
  WHEN 0 THEN 'Insufficient data'
  ELSE (heap_blks_hit / (heap_blks_hit + heap_blks_read)::float)::text
END ratio

FROM

pg_statio_user_tables

ORDER BY

heap_blks_hit / (heap_blks_hit + heap_blks_read + 1)::float DESC;