Re: reducing isolation tests runtime

On 2019-02-13 10:58:50 -0500, Tom Lane wrote:
> Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> writes:
> > On 2019-Feb-13, Tom Lane wrote:
> >> Some of the slower buildfarm critters use MAX_CONNECTIONS to limit
> >> the load on their hosts. As long as the isolation tests honor that,
> >> I don't see a real need for a separate serial schedule.
>
> > MAX_CONNECTIONS was the only reason I didn't push this through. Do you
> > (Andres) have any solution to that?
>
> Doesn't the common pg_regress.c infrastructure handle that?
> We might need to improve isolation_main.c and/or the isolation
> Makefile to make it accessible.

> I suppose that in what I'm thinking about, MAX_CONNECTIONS would be
> interpreted as "max number of concurrent isolation scripts", which
> is not exactly number of connections. A quick and dirty answer
> would be to have isolation_main.c divide the limit by a factor of 4
> or so.

I guess that could work, although it's certainly not too pretty.
Alternatively we could pre-parse the spec files, but that's a bit
annoying given isolationtester.c is a separate c file...

Do you have an idea why we have both max_concurrent_tests *and*
max_connections in pg_regress? ISTM the former isn't really useful given
the latter?

Greetings,

Andres Freund