Re: reducing isolation tests runtime

Hi,

On 2019-02-13 12:41:41 -0500, Tom Lane wrote:
> Andres Freund <andres@anarazel.de> writes:
> > 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?
> 
> No, the former is a static restriction on what the schedule file is
> allowed to contain, the latter is a dynamic restriction (that typically
> is unlimited anyway).

Right, but why don't we allow for more tests in a group, and then use a
default max_connections to limit concurrency? Having larger groups is
advantageous wrt test runtime - it reduces the number of artificial
serialization point where the slowest test slows things down.  Obviously
there's still a few groups that are needed for test interdependency
management, but that's comparatively rare. We have have plenty groups
that are just broken up to stay below max_concurrent_tests.

Greetings,

Andres Freund