Re: remove more archiving overhead

From: Peter Eisentraut <peter(dot)eisentraut(at)enterprisedb(dot)com>
To: Noah Misch <noah(at)leadboat(dot)com>, Nathan Bossart <nathandbossart(at)gmail(dot)com>
Cc: David Steele <david(at)pgmasters(dot)net>, Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com>, robertmhaas(at)gmail(dot)com, masao(dot)fujii(at)oss(dot)nttdata(dot)com, pgsql-hackers(at)postgresql(dot)org
Subject: Re: remove more archiving overhead
Date: 2022-09-17 09:46:39
Message-ID: ebb0f19f-5452-678c-0d19-1b8b260fd331@enterprisedb.com
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On 03.08.22 09:16, Noah Misch wrote:
> On Mon, Aug 01, 2022 at 10:02:19PM -0700, Nathan Bossart wrote:
>> On Sat, Jul 30, 2022 at 11:51:56PM -0700, Noah Misch wrote:
>>> Inviting the administrator to resolve things is more dangerous than just
>>> returning true. I recommend making this text more opinionated and simpler:
>>> libraries must return true. Alternately, if some library has found a good
>>> reason to return false, this paragraph could give the reason. I don't know of
>>> such a reason, though.
>>
>> Your suggestion seems reasonable to me. I've attached a small patch.
>
>> --- a/doc/src/sgml/backup.sgml
>> +++ b/doc/src/sgml/backup.sgml
>> @@ -691,11 +691,9 @@ test ! -f /mnt/server/archivedir/00000001000000A900000065 &amp;&amp; cp pg_wal/0
>> system crashes before the server makes a durable record of archival success,
>> the server will attempt to archive the file again after restarting (provided
>> archiving is still enabled). When an archive library encounters a
>> - pre-existing file, it may return <literal>true</literal> if the WAL file has
>> + pre-existing file, it should return <literal>true</literal> if the WAL file has
>> identical contents to the pre-existing archive and the pre-existing archive
>> - is fully persisted to storage. Alternatively, the archive library may
>> - return <literal>false</literal> anytime a pre-existing file is encountered,
>> - but this will require manual action by an administrator to resolve. If a
>> + is fully persisted to storage. If a
>> pre-existing file contains different contents than the WAL file being
>> archived, the archive library <emphasis>must</emphasis> return
>> <literal>false</literal>.
>
> Works for me. Thanks.

This documentation change only covers archive_library. How are users of
archive_command supposed to handle this?

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