Re: Doc about how to set max_wal_senders when setting minimal wal_level

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От David G. Johnston
Тема Re: Doc about how to set max_wal_senders when setting minimal wal_level
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Msg-id CAKFQuwZx5SeGf9WxozmFj9Udos7ecTR8u_JMeFcucPtULK_buA@mail.gmail.com
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Ответ на Re: Doc about how to set max_wal_senders when setting minimal wal_level  (Japin Li <japinli@hotmail.com>)
Ответы Re: Doc about how to set max_wal_senders when setting minimal wal_level  (Bruce Momjian <bruce@momjian.us>)
Список pgsql-hackers
On Mon, Jul 18, 2022 at 6:27 PM Japin Li <japinli@hotmail.com> wrote:

On Tue, 19 Jul 2022 at 03:58, Bruce Momjian <bruce@momjian.us> wrote:
> On Fri, Jul 15, 2022 at 09:29:20PM +0800, Japin Li wrote:
>>
>> On Fri, 15 Jul 2022 at 08:49, Bruce Momjian <bruce@momjian.us> wrote:
>> > On Tue, Jul  5, 2022 at 08:02:33PM -0400, Tom Lane wrote:
>> >> "Precondition" is an overly fancy word that makes things less clear
>> >> not more so.  Does it mean that setting wal_level = minimal will fail
>> >> if you don't do these other things, or does it just mean that you
>> >> won't be getting the absolute minimum WAL volume?  If the former,
>> >> I think it'd be better to say something like "To set wal_level to minimal,
>> >> you must also set [these variables], which has the effect of disabling
>> >> both WAL archiving and streaming replication."
>> >
>> > I have created the attached patch to try to improve this text.
>>
>> IMO we can add the following sentence for wal_level description, since
>> if wal_level = minimal and max_wal_senders > 0, we cannot start the database.
>>
>> To set wal_level to minimal, you must also set max_wal_senders to 0,
>> which has the effect of disabling both WAL archiving and streaming
>> replication.
>
> Okay, text added in the attached patch.

Thanks for updating the patch! LGTM.


+0.90

Consider changing:

"makes any base backups taken before this unusable"

to:

"makes existing base backups unusable"

As I try to justify this, though, it isn't quite true, maybe:

"makes point-in-time recovery, using existing base backups, unable to replay future WAL."

David J.

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