SELECT
 c . relname ,
 pg_size_pretty ( count ( * ) * 8192) as buffered ,
 round ( 100.0 * count ( * ) /
 (SELECT setting FROM pg_settings WHERE name='shared_buffers')::integer , 1 )
 AS buffers_percent ,
 round ( 100.0 * count ( * ) * 8192 / pg_table_size ( c . oid ) , 1 )
 AS percent_of_relation
 FROM pg_class c
 INNER JOIN pg_buffercache b
 ON b.relfilenode=c.relfilenode
 INNER JOIN pg_database d
 ON (b.reldatabase = d.oid AND d . datname = current_database
( ) )
 GROUP BY c . oid , c . relname
 ORDER BY 3 DESC
 LIMIT 200 ;  

--Статистика seq scan / index scan
SELECT 
      relname, 
      seq_scan, 
      idx_scan, 
      CASE 
        WHEN idx_scan = 0 THEN 100 
        ELSE seq_scan / idx_scan::numeric 
      END AS ratio 
    FROM 
      pg_stat_user_tables 
    ORDER BY 
       ratio desc, seq_scan desc;