Re: Query execution in Perl TAP tests needs work - Mailing list pgsql-hackers

From Thomas Munro
Subject Re: Query execution in Perl TAP tests needs work
Date
Msg-id CA+hUKGJ9m_W4F4M1J9L-LzrhGjt+MAumfUtStYc89gs18R55_w@mail.gmail.com
Whole thread Raw
In response to Re: Query execution in Perl TAP tests needs work  (Noah Misch <noah@leadboat.com>)
Responses Re: Query execution in Perl TAP tests needs work
List pgsql-hackers
On Wed, Aug 30, 2023 at 1:49 AM Noah Misch <noah@leadboat.com> wrote:
> On Tue, Aug 29, 2023 at 04:25:24PM +1200, Thomas Munro wrote:
> > On Tue, Aug 29, 2023 at 1:48 PM Noah Misch <noah@leadboat.com> wrote:
> > > https://github.com/cpan-authors/IPC-Run/issues/166#issuecomment-1288190929
> >
> > Interesting.  But that shows a case with no pipes connected, using
> > select() as a dumb sleep and ignoring SIGCHLD.  In our usage we have
> > pipes connected, and I think select() should return when the child's
> > output pipes become readable due to EOF.  I guess something about that
> > might be b0rked on Windows?  I see there is an extra helper process
> > doing socket<->pipe conversion (hah, that explains an extra ~10ms at
> > the start in my timestamps)...
>
> In that case, let's assume it's not the same issue.

Yeah, I think it amounts to the same thing, if EOF never arrives.

I suspect that we could get ->safe_psql() down to about ~25ms baseline
if someone could fix the posited IPC::Run EOF bug and change its
internal helper process to a helper thread.  Even if we fix tests to
reuse backends, I expect that'd help CI measurably.  (The native way
would be to use pipes directly, changing select() to
WaitForMultipleObjects(), but I suspect IPC::Run might have painted
itself into a corner by exposing the psuedo-pipes and documenting that
they can be used with select().  Oh well.)



pgsql-hackers by date:

Previous
From: Nathan Bossart
Date:
Subject: Re: Is pg_regress --use-existing used by anyone or is it broken?
Next
From: Daniel Gustafsson
Date:
Subject: Re: Is pg_regress --use-existing used by anyone or is it broken?