Mastering PostgreSQL 11 - Second Edition

Investigating caching with pg_buffercache

After this brief introduction to the pageinspect extension, we will turn our focus to the pg_buffercache extension, which allows you to take a deep look at the contents 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_buffercacheView "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 just a number; it identifies the buffer. ...