Re: pg_receivewal starting position

Le jeudi 29 juillet 2021, 11:09:40 CEST Ronan Dunklau a écrit :
> Patch 0001 adds the new READ_REPLICATION_SLOT command.
> It returns for a given slot the type, restart_lsn, flush_lsn,
> restart_lsn_timeline and flush_lsn_timeline.
> The timelines are determined by reading the current timeline history, and
> finding the timeline where we may find the record. I didn't find explicit
> test for eg IDENTIFY_SYSTEM so didn't write one either for this new
> command, but it is tested indirectly in patch 0002.
>
> Patch 0002 makes pg_receivewal use that command if we use a replication slot
> and the command is available, and use the restart_lsn and
> restart_lsn_timeline as a starting point. It also adds a small test to
> check that we start back from the previous restart_lsn instead of the
> current flush position when our destination directory does not contain any
> WAL file.
>
> I also noticed we don't test following a timeline switch. It would probably
> be good to add that, both for the case where we determine the previous
> timeline from the archived segments and when it comes from the new command.
> What do you think ?

Following the discussion at [1], I refactored the implementation into
streamutil and added a third patch making use of it in pg_basebackup itself in
order to fail early if the replication slot doesn't exist, so please find
attached v2 for that.

Best regards,

[1]: https://www.postgresql.org/message-id/flat/
CAD21AoDYmv0yJMQnWtCx_kZGwVZnkQSTQ1re2JNSgM0k37afYQ%40mail.gmail.com

--
Ronan Dunklau