From: Andres Freund <andres@anarazel.de>
To: David Steele <david@pgmasters.net>
Cc: Michael Paquier <michael@paquier.xyz>
Cc: pgsql-committers@postgresql.org
Subject: Re: pgsql: Make WAL segment size configurable at initdb time.
Date: Thu, 20 Sep 2018 18:23:54 -0700
Message-ID: <20180921012354.mvkql65radrpv4gx@alap3.anarazel.de> (raw)
In-Reply-To: <4b5568f5-72b7-5355-3450-973e11447569@pgmasters.net>
References: <E1duXBW-0003QB-4d@gemulon.postgresql.org>
<68ea97d6-2ed9-f339-e57d-ab3a33caf3b1@pgmasters.net>
<20180920235932.GD1338@paquier.xyz>
<4b5568f5-72b7-5355-3450-973e11447569@pgmasters.net>
On 2018-09-20 21:14:51 -0400, David Steele wrote:
> On 9/20/18 7:59 PM, Michael Paquier wrote:
> > On Thu, Sep 20, 2018 at 11:48:08AM -0400, David Steele wrote:
> >> </term>
> >> <listitem>
> >> <para>
> >> - Reports the number of blocks (pages) in a WAL segment file.
> >> - The total size of a WAL segment file in bytes is equal to
> >> - <varname>wal_segment_size</varname> multiplied by <varname>wal_block_size</varname>;
> >> - by default this is 16MB. See <xref linkend="wal-configuration"/> for
> >> + Reports the size of write ahead log segments.
> >> + The default value is 16MB. See <xref linkend="wal-configuration"/> for
> >> more information.
> >> </para>
> >> </listitem>
> >
> > The GUC wal_segment_size reports as well 16MB in v10 or older versions,
> > so shouldn't the mention to wal_block_size be removed even further down?
>
> Oddly, the GUC reports 16GB on `show wal_segment_size` but you get 2048
> when querying pg_settings. I thought that was just the normal behavior
> for older versions -- and it might be a problem to change it.
16*M*B, right? If so, that's normal - pg_settings just reports the
values in the underlying unit - which is XLOG_BLCKSZ, compile-time
defaulting to 8KB. 8192 * 2048 = 16MB. That's the same in various other
settings.
Greetings,
Andres Freund
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: pgsql-committers@postgresql.org
Cc: andres@anarazel.de, david@pgmasters.net, michael@paquier.xyz
Subject: Re: pgsql: Make WAL segment size configurable at initdb time.
In-Reply-To: <20180921012354.mvkql65radrpv4gx@alap3.anarazel.de>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox