Re: remove more archiving overhead

On Sat, Sep 17, 2022 at 11:46:39AM +0200, Peter Eisentraut wrote:
>> > --- a/doc/src/sgml/backup.sgml
>> > +++ b/doc/src/sgml/backup.sgml
>> > @@ -691,11 +691,9 @@ test ! -f /mnt/server/archivedir/00000001000000A900000065 && 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?

I believe users of archive_command need to do something similar to what is
described here. However, it might be more reasonable to expect
archive_command users to simply return false when there is a pre-existing
file, as the deleted text notes. IIRC that is why I added that sentence
originally.

--
Nathan Bossart
Amazon Web Services: https://aws.amazon.com