Re: [BUGS] BUG #14230: Wrong timeline returned by pg_stop_backup on a standby

On 08/07/16 13:10, Michael Paquier wrote:
> On Fri, Jul 8, 2016 at 6:40 PM, Marco Nenciarini
> <marco(dot)nenciarini(at)2ndquadrant(dot)it> wrote:
>> The resulting backup is working perfectly, because Postgres has no use
>> for pg_stop_backup LSN, but this can confuse any tool that uses the stop
>> LSN to figure out which WAL files are needed by the backup (in this case
>> the only file needed is the one containing the start checkpoint).
>>
>> After some discussion with Álvaro, my proposal is to avoid that by
>> returning the stoppoint as the maximum between the startpoint and the
>> min_recovery_end_location, in case of backup from the standby.
>
> You are facing a pattern similar to the problem reported already on
> this thread by Horiguchi-san:
> http://www.postgresql.org/message-id/20160609.215558.118976703.horiguchi.kyotaro@lab.ntt.co.jp
> And it seems to me that you are jumping to an incorrect conclusion,
> what we'd want to do is to update a bit more aggressively the minimum
> recovery point in cases on a node in recovery in the case where no
> buffers are flushed by other backends.
>

Yes, it is exactly the same bug. My proposal was based on the assumption
that it were only a cosmetic issue, but given that it can trigger
errors, I agree that the right solution is to advance the minimum
recovery point in that case.

Regards,
Marco

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Marco Nenciarini - 2ndQuadrant Italy
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