Re: max_wal_size

From: Pavel Luzanov <p(dot)luzanov(at)postgrespro(dot)ru>
To: Bruce Momjian <bruce(at)momjian(dot)us>
Cc: "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com>, pluzanov(at)postgrespro(dot)ru, pgsql-docs(at)lists(dot)postgresql(dot)org
Subject: Re: max_wal_size
Date: 2020-06-02 20:42:01
Message-ID: 26906a54-d7cb-2f8e-eed7-e31660024694@postgrespro.ru
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Hello,

On 02.06.2020 22:35, Bruce Momjian wrote:
> On Thu, May 28, 2020 at 12:21:14PM +0300, p(dot)luzanov(at)postgrespro(dot)ru wrote:
>> WAL |-----------|-----+-----|-----+-----|-----+----->
>>
>> a b c
>> CP +-----+ +-----+ +-----+
>> b e b e b e
>>
>> Checkpointer process for point A starts at a(b) and ends at a(e).
>> At the end of the work, CP makes a WAL record(plus symbol on WAL line).
>>
>> Back to the max_wal_size description:
>> "Maximum size to let the WAL grow to between automatic WAL checkpoints."
>>
>> As I understand now, this is true when we talk about the checkpoint as a
>> process.
>> "Maximum size to let the WAL grow to between a(b) and b(e), between b(b) and c
>> (e), etc".
> What if we say:
>
> "Maximum size to let the WAL grow during automatic WAL checkpoints."
>
> That highlights the "process" part.
>
Really, "during" is associated with the process, while "between" with
points.

If there is no objection, simpe patch attached.

-----
Pavel Luzanov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company

Attachment Content-Type Size
docs_max_wal_size.patch text/x-patch 603 bytes

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