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

On Mon, Jan 18, 2016 at 7:08 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:
>
> On 2015-12-21 16:26:25 +0900, Michael Paquier wrote:
> > On Sun, Dec 20, 2015 at 10:14 PM, Michael Paquier
> > <michael(dot)paquier(at)gmail(dot)com> wrote:
> > > Speaking of which, this patch was registered in this CF, I am moving
> > > it to the next as a bug fix.
> >
> > I found a stupid bug in my previous patch: when issuing XLOG_SWITCH it
> > is possible that the return LSN pointer is on the new segment that has
> > been forcibly archived if RequestXLogSwitch is called multiple times
> > and that subsequent calls are not necessary. Patch updated.
>
> I find this patch rather unsatisfactory. Yes, it kinda solves the
> problem of archive timeout, but it leaves the bigger and longer standing
> problems of unneccessary checkpoints with wal_level=hs in place. It's
> also somewhat fragile in my opinion.
>
> I think we rather want a per backend (or perhaps per wal insertion lock)
> flag that says 'last relevant record inserted at', and a way to not set
> that during insertion. Then during a checkpoint or the relevant bgwriter
> code, we look wether anything relevant happened in any backend since the
> last time we performed a checkpoint/logged a running xacts snapshot.
>

Sounds to be a more robust way of dealing with this problem. Michael,
if you don't disagree with above proposal, then we can mark this patch
as Waiting on Author?

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