Received: from malur.postgresql.org ([217.196.149.56])
	by arkaria.postgresql.org with esmtps
 (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256)
	(Exim 4.92)
	(envelope-from <pgsql-hackers-owner+archive@lists.postgresql.org>)
	id 1jxNjM-0000vC-57
	for pgsql-hackers@arkaria.postgresql.org; Mon, 20 Jul 2020 04:48:48 +0000
Received: from localhost ([127.0.0.1] helo=malur.postgresql.org)
	by malur.postgresql.org with esmtp (Exim 4.92)
	(envelope-from <pgsql-hackers-owner+archive@lists.postgresql.org>)
	id 1jxNjL-0008HW-3A
	for pgsql-hackers@arkaria.postgresql.org; Mon, 20 Jul 2020 04:48:47 +0000
Received: from magus.postgresql.org ([2a02:c0:301:0:ffff::29])
	by malur.postgresql.org with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256)
	(Exim 4.92)
	(envelope-from <masao.fujii@oss.nttdata.com>)
	id 1jxNjK-0008HP-SA
	for pgsql-hackers@lists.postgresql.org; Mon, 20 Jul 2020 04:48:46 +0000
Received: from oss.nttdata.com ([49.212.34.109])
	by magus.postgresql.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256)
	(Exim 4.92)
	(envelope-from <masao.fujii@oss.nttdata.com>)
	id 1jxNjH-000700-QV
	for pgsql-hackers@postgresql.org; Mon, 20 Jul 2020 04:48:46 +0000
Received: from hnk.local (p2360113-ipbf2222funabasi.chiba.ocn.ne.jp
 [114.177.58.113])
	by oss.nttdata.com (Postfix) with ESMTPSA id 3CD8760342;
	Mon, 20 Jul 2020 13:48:38 +0900 (JST)
X-Virus-Status: Clean
X-Virus-Scanned: clamav-milter 0.102.3 at oss.nttdata.com
Subject: Re: max_slot_wal_keep_size and wal_keep_segments
To: David Steele <david@pgmasters.net>,
 Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Cc: alvherre@2ndquadrant.com, pgsql-hackers@postgresql.org
References: <6e4f9605-97f3-7eba-f989-4ae41d637d2f@oss.nttdata.com>
 <20200709.134743.1136524996274963021.horikyota.ntt@gmail.com>
 <866c681c-3082-7010-cc9e-bf3b9483c991@oss.nttdata.com>
 <20200713.160111.1304073320526166244.horikyota.ntt@gmail.com>
 <d8d60d1a-5233-cbcc-099d-ee34033ea619@oss.nttdata.com>
 <87269252-772e-2daf-9955-674a24e24de6@pgmasters.net>
 <efffe8f2-63ea-fe8c-68db-244aa27a63ef@oss.nttdata.com>
 <6479e9a4-0a9d-0772-0401-2c5d0de03ea7@pgmasters.net>
From: Fujii Masao <masao.fujii@oss.nttdata.com>
Message-ID: <dc4768f2-1eff-d2fc-35ba-6b2985b7cb6c@oss.nttdata.com>
Date: Mon, 20 Jul 2020 13:48:37 +0900
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:68.0)
 Gecko/20100101 Thunderbird/68.10.0
MIME-Version: 1.0
In-Reply-To: <6479e9a4-0a9d-0772-0401-2c5d0de03ea7@pgmasters.net>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 8bit
List-Id: <pgsql-hackers.lists.postgresql.org>
List-Help: <https://lists.postgresql.org/manage/>
List-Subscribe: <https://lists.postgresql.org/manage/>
List-Post: <mailto:pgsql-hackers@lists.postgresql.org>
List-Owner: <mailto:pgsql-hackers-owner@lists.postgresql.org>
List-Archive: <https://www.postgresql.org/list/pgsql-hackers>
Precedence: bulk



On 2020/07/17 20:24, David Steele wrote:
> 
> On 7/17/20 5:11 AM, Fujii Masao wrote:
>>
>>
>> On 2020/07/14 20:30, David Steele wrote:
>>> On 7/14/20 12:00 AM, Fujii Masao wrote:
>>>>
>>>> The patch was no longer applied cleanly because of recent commit.
>>>> So I updated the patch. Attached.
>>>>
>>>> Barring any objection, I will commit this patch.
>>>
>>> This doesn't look right:
>>>
>>> +   the <xref linkend="guc-wal-keep-size"/> most recent megabytes
>>> +   WAL files plus one WAL file are
>>>
>>> How about:
>>>
>>> +   <xref linkend="guc-wal-keep-size"/> megabytes of
>>> +   WAL files plus one WAL file are
>>
>> Thanks for the comment! Isn't it better to keep "most recent" part?
>> If so, what about either of the followings?
>>
>> 1. <xref linkend="guc-wal-keep-size"/> megabytes of WAL files plus
>>      one WAL file that were most recently generated are kept all time.
>>
>> 2. <xref linkend="guc-wal-keep-size"/> megabytes + <xref linkend="guc-wal-segment-size"> bytes
>>      of WAL files that were most recently generated are kept all time.
> 
> "most recent" seemed implied to me, but I see your point.
> 
> How about:
> 
> +   the most recent <xref linkend="guc-wal-keep-size"/> megabytes of
> +   WAL files plus one additional WAL file are

I adopted this and pushed the patch. Thanks!

Also we need to update the release note for v13. What about adding the following?

------------------------------------
Rename configuration parameter wal_keep_segments to wal_keep_size.

This allows how much WAL files to retain for the standby server, by bytes instead of the number of files.
If you previously used wal_keep_segments, the following formula will give you an approximately equivalent setting:

wal_keep_size = wal_keep_segments * wal_segment_size (typically 16MB)
------------------------------------


Regards,

-- 
Fujii Masao
Advanced Computing Technology Center
Research and Development Headquarters
NTT DATA CORPORATION