Re: Race condition in recovery?

On 6/12/21 10:20 AM, Tom Lane wrote:
> Andrew Dunstan <andrew@dunslane.net> writes:
>> I have pushed a fix, tested on a replica of fairywren/drongo,
> This bit seems a bit random:
>
>  # WAL segment, this is enough to guarantee that the history file was
>  # archived.
>  my $archive_wait_query =
> -  "SELECT '$walfile_to_be_archived' <= last_archived_wal FROM pg_stat_archiver;";
> +  "SELECT coalesce('$walfile_to_be_archived' <= last_archived_wal, false) " .
> +  "FROM pg_stat_archiver";
>  $node_standby->poll_query_until('postgres', $archive_wait_query)
>    or die "Timed out while waiting for WAL segment to be archived";
>  my $last_archived_wal_file = $walfile_to_be_archived;
>
> I wonder whether that is a workaround for the poll_query_until bug
> I proposed to fix at [1].
>
>             regards, tom lane
>
> [1] https://www.postgresql.org/message-id/2130215.1623450521%40sss.pgh.pa.us



No, it's because I found it annoying and confusing that there was an
invisible result when last_archived_wal is null.


cheers


andrew

--
Andrew Dunstan
EDB: https://www.enterprisedb.com