select c.relname,count(*) as buffers from pg_buffercache b inner join pg_class c on b.relfilenode = pg_relation_filenode(c.oid) and b.reldatabase in (0,(select oid from pg_database where datname = current_database())) group by c.relname order by 2 desc;

亲测可用

如果报错：ERROR: relation "pg_buffercache" does not exist

解决办法：\c DB名

CREATE EXTENSION IF NOT EXISTS pg_buffercache;

然后重新执行语句即可