Re: "backend process" confused with "server process"

From: jian he <jian(dot)universality(at)gmail(dot)com>
To: Daniel Gustafsson <daniel(at)yesql(dot)se>
Cc: "Andrey M(dot) Borodin" <x4mmm(at)yandex-team(dot)ru>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: "backend process" confused with "server process"
Date: 2024-04-16 03:42:17
Message-ID: CACJufxH4JoG+bJDfWAbe6u2qzZ-Ru+Y=wiQJ75d=_QCLoP=c+Q@mail.gmail.com
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On Mon, Apr 15, 2024 at 5:27 PM Daniel Gustafsson <daniel(at)yesql(dot)se> wrote:
>
> > On 15 Apr 2024, at 11:07, Andrey M. Borodin <x4mmm(at)yandex-team(dot)ru> wrote:
> >> On 15 Apr 2024, at 14:01, jian he <jian(dot)universality(at)gmail(dot)com> wrote:
>
> >> "is not a PostgreSQL server process" is the same thing as "not a
> >> PostgreSQL backend process”?
> >
> > As far as I understand, backend is something attached to frontend.
> > There might be infrastructure processes like syslogger or stats collector, client can signal it too.
>
> I think that's a good summary, in line with the glossary in our docs where we
> define "Auxiliary process" and "Backend (process)" (but not PostgreSQL server
> process which maybe we should?). "PostgreSQL server process" is used in copy
> to/from error messaging as well in what seems to be a user-freindly way to say
> "backend". In the docs we mostly use "server process" to mean a process
> running in the operating system on the server. In a few places we use
> "database server process" too when talking about backends.
>
> In the case of pg_log_backend_memory_contexts(), the function comment states
> the following:
>
> "Signal a backend or an auxiliary process to log its memory contexts"
>
> So in this case, "PostgreSQL server process" seems like the correct term.
>

in [1] (pg_stat_activity)
does "PostgreSQL server process" means all backend_type:
autovacuum launcher, autovacuum worker, logical replication launcher,
logical replication worker, parallel worker, background writer, client
backend, checkpointer, archiver, standalone backend, startup,
walreceiver, walsender and walwriter.
?

and
`PostgreSQL backend process`
means only `client backend`?

I aslo found an minor inconsistency.
`Autovacuum (process)`
is not the same thing as
`autovacuum launcher`
?

but there is a link from `autovacuum launcher` to `Autovacuum (process)`.

[1] https://www.postgresql.org/docs/current/monitoring-stats.html#MONITORING-PG-STAT-ACTIVITY-VIEW
[2] https://www.postgresql.org/docs/current/glossary.html

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