Re: TAP test utility module 'PG_LSN.pm'

On Tue, 1 Dec 2020 at 13:58, Michael Paquier <michael@paquier.xyz> wrote:
>
> On Tue, Dec 01, 2020 at 12:03:41PM +0800, Craig Ringer wrote:
> > I'd like to share the attached PG_LSN.pm module that I use when
> > writing TAP tests. I suggest that it be considered for inclusion in
> > core.
> >
> > It defines a Perl datatype PG_LSN with operator support, so you can
> > write things like
> >
> >     cmp_ok($got_lsn, "<", $expected_lsn, "testname")
> >
> > in TAP tests and get sensible results without any concern for LSN
> > representation details, locale, etc. You can subtract LSNs to get a
> > byte difference too.
>
> In my experience, any TAP tests making use of LSN operations can just
> let the backend do the maths, so I am not much a fan of duplicating
> that stuff in a perl module.  Wouldn't it be better to add an
> equivalent of your add() function in the backend then?  That could
> also get tested in the main regression test suite.

I find it convenient not to have as much log spam. Also, IIRC I needed
it at some points where the target backend(s) were down while I was
testing something related to a backend that was still in recovery and
not yet available for querying.

I don't really mind though, I'm just sharing what I have found useful.