Subject: Re: pgsql: Make WAL segment size configurable at initdb time.
From: David Steele <david@pgmasters.net>
To: Michael Paquier <michael@paquier.xyz>, Andres Freund <andres@anarazel.de>
Cc: pgsql-committers@postgresql.org
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Message-ID: <bb1d0061-f1f9-8c62-e347-89dd02ad97da@pgmasters.net>
Date: Fri, 5 Oct 2018 17:41:56 +0100
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On 9/21/18 12:44 PM, David Steele wrote:
> On 9/21/18 12:53 AM, Michael Paquier wrote:
>> On Thu, Sep 20, 2018 at 06:23:54PM -0700, Andres Freund wrote:
>>> 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.
>>
>> Would it bring less confusion if we append something like "When querying
>> pg_settings"?  I can see David's point the current phrasing is
>> confusing: we don't know if this comes from pg_settings or from SHOW.
>> It obviously refers to the former, but one can understand that it refers
>> to the latter.
>>
>> A second parameter in config.sgml where this formulation is used is
>> segment_size.
> 
> That's why I used a default of 16MB instead of the byte value, because
> segment_size used 1GB instead of the byte value.

Not sure where we are on this, but for the record I still think the 
description in PG11 needs to be corrected as in the patch.  It doesn't 
need to be back-patched and the default seems correct to me.

Thanks,
-- 
-David
david@pgmasters.net