pg_buffercache usage

pg_buffercache.sql

create extension pg_buffercache;

-- 查看哪个数据库占用的缓存最多
select datname, count(*), count(*) filter (where isdirty = true) as dirty
  from pg_buffercache as b, pg_database as d
  where d.oid = b.reldatabase
  group by rollup (1);

-- 查看指定数据库中哪张表占用的缓存最多
select relname, relkind, count(*), count(*) filter (where isdirty = true) as dirty
  from pg_buffercache as b, pg_database as d, pg_class as c
  where d.oid = b.reldatabase and c.relfilenode = b.relfilenode and datname = 'postgres'
  group by 1, 2
  order by 3 desc
  limit 10;