Horton

Re: pg_stat_bgwriter.buffers_backend is pretty meaningless (and more?)

Pavel Luzanov <p.luzanov@postgrespro.ru>

View thread View on postgr.es
From: Pavel Luzanov <p.luzanov@postgrespro.ru>
To: Melanie Plageman <melanieplageman@gmail.com>
Cc: Justin Pryzby <pryzby@telsasoft.com>, Andres Freund <andres@anarazel.de>, Kyotaro Horiguchi <horikyota.ntt@gmail.com>, tgl@sss.pgh.pa.us, vignesh21@gmail.com, lukas@fittl.com, alvherre@alvh.no-ip.org, magnus@hagander.net, pgsql-hackers@postgresql.org, thomas.munro@gmail.com, m.sakrejda@gmail.com
Date: 2023-04-10T07:41:38Z
Lists: pgsql-hackers

Attachments

On 05.04.2023 03:41, Melanie Plageman wrote:
> On Tue, Apr 4, 2023 at 4:35 PM Pavel Luzanov <p.luzanov@postgrespro.ru> wrote:
>
>> After a little thought... I'm not sure about the term 'bootstrap
>> process'. I can't find this term in the documentation.
> There are various mentions of "bootstrap" peppered throughout the docs
> but no concise summary of what it is. For example, initdb docs mention
> the "bootstrap backend" [1].
>
> Interestingly, 910cab820d0 added "Bootstrap superuser" in November. This
> doesn't really cover what bootstrapping is itself, but I wonder if that
> is useful? If so, you could propose a glossary entry for it?
> (preferably in a new thread)

I'm not sure if this is the reason for adding a new entry in the glossary.

>> Do I understand correctly that this is a postmaster? If so, then the
>> postmaster process is not shown in pg_stat_activity.
> No, bootstrap process is for initializing the template database. You
> will not be able to see pg_stat_activity when it is running.

Oh, it's clear to me now. Thank you for the explanation.

> You can query pg_stat_activity from single user mode, so it is relevant
> to pg_stat_activity also. I take your point that bootstrap mode isn't
> relevant for pg_stat_activity, but I am hesitant to add that distinction
> to the pg_stat_io docs since the reason you won't see it in
> pg_stat_activity is because it is ephemeral and before a user can access
> the database and not because stats are not tracked for it.
>
> Can you think of a way to convey this?

See my attempt attached.
I'm not sure about the wording. But I think we can avoid the term 
'bootstrap process'
by replacing it with "database cluster initialization", which should be 
clear to everyone.

-- 
Pavel Luzanov
Postgres Professional: https://postgrespro.com

Commits

  1. Stabilize pg_stat_io writes test

  2. Fix flakey pg_stat_io test

  3. Suppress more compiler warnings in new pgstats code.

  4. Suppress compiler warnings in new pgstats code.

  5. Add tests for pg_stat_io

  6. Create regress_tblspc in test_setup

  7. Add pg_stat_io view, providing more detailed IO statistics

  8. pgstat: Track more detailed relation IO statistics

  9. pgstat: Infrastructure for more detailed IO statistics

  10. doc: Fix some issues in logical replication section

  11. Manual cleanup and pgindent of pgstat and bufmgr related code

  12. Have the planner consider Incremental Sort for DISTINCT

  13. Use actual backend IDs in pg_stat_get_backend_idset() and friends.

  14. Remove redundant call to pgstat_report_wal()

  15. Add BackendType for standalone backends

  16. Initialize backend status reporting during bootstrap.