Mastering PostgreSQL 9.6

Investigating caching with pg_buffercache

After this brief introduction to the pageinspect extension, I want to focus your attention on the pg_buffercache extension, which allows you to take a deep look at the content of your I/O cache:

test=# CREATE EXTENSION pg_buffercache; CREATE EXTENSION 

The pg_buffercache extension provides you with a view containing a couple of fields:

test=# \d pg_buffercache        View "public.pg_buffercache"       Column      |   Type   | Modifiers  ------------------+----------+-----------  bufferid         | integer  |   relfilenode      | oid      |   reltablespace    | oid      |   reldatabase      | oid      |   relforknumber    | smallint |   relblocknumber   | bigint   |   isdirty          | boolean  |   usagecount       | smallint |   pinning_backends | integer  |  

The bufferid field is ...