Re: New instability in stats regression test

Andres Freund <andres(at)anarazel(dot)de> writes:
> I am probably under-caffeinated: What precisely is the potential race? Just
> that the timestamps on some system might not be granular enough?

The problem as I see it is that this test:

SELECT :io_stats_post_reset < :io_stats_pre_reset;

requires an assumption that less I/O has happened since the commanded
reset action than happened before it (extending back to the previous
reset, or cluster start). Since concurrent processes might be doing
I/O, this has a race condition. If we are slow enough about obtaining
:io_stats_post_reset, the test *will* fail eventually. But the shorter
the distance back to the previous reset, the bigger the odds of
observable trouble; thus Michael's concern that adding more reset
tests in future would increase the risk of failure.

regards, tom lane