Re: pg_stat_bgwriter.buffers_backend is pretty meaningless (and more?)

On Tue, Mar 07, 2023 at 10:18:44AM -0800, Andres Freund wrote:
> Hi,
>
> On 2023-03-06 15:21:14 -0500, Melanie Plageman wrote:
> > Good point. Attached is what you suggested. I committed the transaction
> > before the drop table so that the statistics would be visible when we
> > queried pg_stat_io.
>
> Pushed, thanks for the report, analysis and fix, Tom, Horiguchi-san, Melanie.

There's a 2nd portion of the test that's still flapping, at least on
cirrusci.

The issue that Tom mentioned is at:
SELECT :io_sum_shared_after_writes > :io_sum_shared_before_writes;

But what I've seen on cirrusci is at:
SELECT :io_sum_shared_after_writes > :io_sum_shared_before_writes;

https://api.cirrus-ci.com/v1/artifact/task/6701069548388352/log/src/test/recovery/tmp_check/regression.diffs
https://api.cirrus-ci.com/v1/artifact/task/5355168397524992/log/src/test/recovery/tmp_check/regression.diffs
https://api.cirrus-ci.com/v1/artifact/task/6142435751886848/testrun/build/testrun/recovery/027_stream_regress/log/regress_log_027_stream_regress

It'd be neat if cfbot could show a histogram of test failures, although
I'm not entirely sure what granularity would be most useful: the test
that failed (027_regress) or the way it failed (:after_write >
:before_writes). Maybe it's enough to show the test, with links to its
recent failures.

--
Justin