Re: WAL usage calculation patch

вт, 18 февр. 2020 г. в 06:23, Thomas Munro <thomas.munro@gmail.com>:
> On Mon, Feb 10, 2020 at 8:20 PM Craig Ringer <craig@2ndquadrant.com> wrote:
> > On Wed, 5 Feb 2020 at 21:36, Kirill Bychik <kirill.bychik@gmail.com> wrote:
> > > Patch is separated in two parts: core changes and pg_stat_statements
> > > additions. Essentially the extension has its schema updated to allow
> > > two more fields, docs updated to reflect the change. Patch is prepared
> > > against master branch.
> > >
> > > Please provide your comments and/or code findings.
> >
> > I like the concept, I'm a big fan of anything that affordably improves
> > visibility into Pg's I/O and activity.
>
> +1
>
> > To date I've been relying on tools like systemtap to do this sort of
> > thing. But that's a bit specialised, and Pg currently lacks useful
> > instrumentation for it so it can be a pain to match up activity by
> > parallel workers and that sort of thing. (I aim to find time to submit
> > a patch for that.)
>
> (I'm interested in seeing your conference talk about that!  I did a
> bunch of stuff with static probes to measure PHJ behaviour around
> barrier waits and so on but it was hard to figure out what stuff like
> that to put in the actual tree, it was all a bit
> use-once-to-test-a-theory-and-then-throw-away.)
>
> Kirill, I noticed that you included a regression test that is failing.  Can
> this possibly be stable across machines or even on the same machine?
> Does it still pass for you or did something change on the master
> branch to add a new WAL record since you posted the patch?

Thank you for testing the patch and running extension checks. I assume
the patch applies without problems.

As for the regr test, it apparently requires some rework. I didn't pay
attention enough to make sure the data I check is actually meaningful
and isolated enough to be repeatable.

Please consider the extension part of the patch as WIP, I'll resubmit
the patch once I get a stable and meanngful test up. Thanks for
finding it!

> query | calls | rows | wal_write_bytes | wal_write_records
>  -------------------------------------------+-------+------+-----------------+-------------------
> - CREATE INDEX test_b ON test(b)            |     1 |    0 | 1673 |
>             16
> - DROP FUNCTION IF EXISTS PLUS_ONE(INTEGER) |     1 |    0 |   56 |
>              1
> + CREATE INDEX test_b ON test(b)            |     1 |    0 | 1755 |
>             17
> + DROP FUNCTION IF EXISTS PLUS_ONE(INTEGER) |     1 |    0 |    0 |
>              0