查看安装情况：
pgbenchdb=# \dx
List of installed extensions
Name | Version | Schema | Description
----------------+---------+------------+---------------------------------
pg_buffercache | 1.4 | public | examine the shared buffer cache
plpgsql | 1.0 | pg_catalog | PL/pgSQL procedural language
2.更新一个表
pgbenchdb=# update pgbench_accounts set filler=filler;
3.方便查看，建立一个视图
create view pg_buffercache_v as
select bufferid,
(select c.relname
from pg_class c
where pg_relation_filenode(c.oid) = b.relfilenode
) relname,
case relforknumber
when 0 then 'main'
when 1 then 'fsm'
when 2 then 'vm'
end relfork,
relblocknumber,
isdirty,
usagecount
from pg_buffercache b
where b.reldatabase in (0,(select oid from pg_database where datname=current_database()))
and b.usagecount is not null;
4.查看该表 缓冲区情况
pgbenchdb=# select * from pg_buffercache_v where relname='pgbench_accounts';
bufferid | relname | relfork | relblocknumber | isdirty | usagecount
----------+------------------+---------+----------------+---------+------------
2 | pgbench_accounts | main | 34060 | t | 1
3 | pgbench_accounts | main | 866375 | t | 4
4 | pgbench_accounts | main | 866266 | t | 2
5 | pgbench_accounts | main | 866163 | f | 0