Re: Re: BUG #13685: Archiving while idle every archive_timeout with wal_level hot_standby

On Thu, Feb 4, 2016 at 6:40 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:
>
> On 2016-02-04 18:21:41 +0530, Amit Kapila wrote:
> > I think generally it is good idea, but one thing worth a thought is that
> > by doing so, we need to acquire all WAL Insertion locks every
> > LOG_SNAPSHOT_INTERVAL_MS to check the last_insert_pos for
> > every slot, do you think it is matter of concern in any way for write
> > workloads or it won't effect as we need to do this periodically?
>
> Michael and I just had an in-person discussion, and one of the topics
> was that. The plan was basically to adapt the patch to:
> 1) Store the progress lsn inside the wal insert lock
> 2) Change the HasActivity API to return an the last LSN at which there
> was activity, instead of a boolean.
> 2) Individually acquire each insert locks's lwlock to get it's progress
> LSN, but not the exclusive insert lock. We need the lwllock to avoid
> a torn 8byte read on some platforms.
>
> I think that mostly should address your concerns?
>

Yes, this sounds better and in-anycase we can do some benchmarks
to verify the same once patch is in shape.

With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com