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

On Tue, Jan 19, 2016 at 1:28 PM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> On Mon, Jan 18, 2016 at 7:08 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:
>> 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.

Check.

>> 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.

And in this case, the last relevant record would be caused by a forced
segment switch or a checkpoint record, right? Doing that per WAL
insertion lock seems more scalable to me. I haven't looked at the code
yet though to see how that would work out.

> 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?

Yeah let's do so. I'll think more about this thing.
--
Michael