Re: [HACKERS] Autovacuum loose ends

On Fri, 12 Aug 2005 18:42:09 -0400
Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> wrote:

> On Fri, Aug 12, 2005 at 03:16:04PM -0700, Mark Wong wrote:
> > On Fri, 12 Aug 2005 17:49:41 -0400
> > Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> wrote:
> >
> > > Notice how the subindexes are wrong ... I think it should be 1:3 for
> > > i_orders, no? Apparently indexes_scan.data has the same problem.
> >
> > Whoops! I think I fixed it for real now and the charts should be
> > updated now. It was broken slightly more previously.
>
> Hmm, did you fix the 42 case only? The other one is broken too ...

The other dev4-015 cases should be fixed too.

> Also, it seems the "tran_lock.out" file captured wrong input -- I think
> you mean "WHERE transactionid IS NULL" in the query instead of "WHERE
> transaction IS NULL".

Hmm, ok I can try that in a future test run. I'm not very familiar with
this table, what's the difference between transaction and transactionid?

> I wonder what the big down-spikes (?) at minutes ~45 and ~85 correspond
> to. Are those checkpoints? The IO vmstat chart would indicate that, I
> think.

That's correct, those should be checkpoints.

> Anyway, it's interesting to see the performance go up with autovacuum
> on. I certainly didn't expect that in this kind of test.

I think in Mary's case it was hurting, but she's running the workload
dramatically different. I think she was planning to revisit that after
we sort out what's going on with the grouped WAL writes.

Mark