Re: [HACKERS] Create replication slot in pg_basebackup if requestedand not yet present

On 9/11/17 03:11, Michael Banck wrote:
> So my patch only moves the slot creation slightly further forward,
> AFAICT.

I have committed this patch, along with some associated cleanup.

> AIUI, wal streaming always begins at last checkpoint and from my tests
> the restart_lsn of the created replication slot is also before that
> checkpoint's lsn. However, I hope somebody more familiar with the
> WAL/replication slot code could comment on that.  What I dropped in the
> refactoring is the RESERVE_WAL that used to be there when the temporary
> slot gets created, I have readded that now.

I had to make some changes to that, because the way your patch was
written it would use RESERVE_WAL also for the calls from pg_receivewal
--create-slot, which would have been a behavior change.  So I added
another argument to CreateReplicationSlot() to control that.

> I also added a TAP test case that tries to check that the restart_lsn is
> lower than the checkpoint_lsn, which appears to be the case.

I think that test was written incorrectly, because it didn't actually
check the $checkpoint_lsn that it read.  I have not included that test
in the committed patch.  Feel free to send another patch if you want to
add more or different tests.

-- 
Peter Eisentraut              http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services


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