public inbox for [email protected]  

help / color / mirror / Atom feed

From: Laurenz Albe <[email protected]>
To: Scott Ribe <[email protected]>
To: pgsql-admin <[email protected]>
Subject: Re: pg_stat_statements, write activity
Date: Fri, 16 May 2025 21:37:26 +0200
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>

On Fri, 2025-05-16 at 11:10 -0600, Scott Ribe wrote:
> I would guess that shared_blks_dirtied in pg_stat_statements is basically the
> count of blocks which will be logged into WAL and written back during checkpoints.
> So then what is shared_blks_written? Or do I misunderstand shared_blks_dirtied???

The statistics track how many blocks were dirtied or written by the backend process
that performed the SQL statement.  Typically, the backend only dirties the blocks,
but doesn't write them to disk itself.  This is done by the checkpointer or the
background writer later on.

Sometimes, a backend writes a block to disk itself.  This might happen if a lot
of cache pressure, but usually it happens when the table is extended with new
blocks.

Yours,
Laurenz Albe

reply

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Reply to all the recipients using the --to and --cc options:
  reply via email

  To: [email protected]
  Cc: [email protected], [email protected], [email protected]
  Subject: Re: pg_stat_statements, write activity
  In-Reply-To: <[email protected]>

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

This inbox is served by agora; see mirroring instructions
for how to clone and mirror all data and code used for this inbox