centos 6.8 + postgresql 9.6 + pg_buffercache

pg_buffercache 主要是用来查看pgsql数据库 shared_pool 的使用情况,注意:是查看使用情况

create extension pg_buffercache
;
select *
from pg_buffercache
;
SELECT name,setting,unit,current_setting(name) 
  FROM pg_settings 
 WHERE 1=1
   and name='shared_buffers'
;

name	setting	unit	current_setting
shared_buffers	16384	8kB	128MB

计算
select 16384*8/1024 = 128
;

?column?

true

查看使用情况

select d.datname,
       c.relname,
       c.relkind,
       count(*) as buffers
  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())
 where 1=1
group by d.datname,
         c.relname,
         c.relkind
order by d.datname,4 desc
;