Re: Extracting cross-version-upgrade knowledge from buildfarm client

On 2023-Jul-19, Andrew Dunstan wrote:

> 
> On 2023-07-19 We 07:05, Alvaro Herrera wrote:
> > I just hit a snag testing this.  It turns out that the
> > PostgreSQL::Version comparison stuff believes that 16beta2 < 16, which
> > sounds reasonable.  However, because of that, the AdjustUpgrade.pm
> > stanza that tries to drop tables public.gtest_normal_child{2} in
> > versions earlier than 16 fails, because by 16 these tables are dropped
> > in the test itself rather than left to linger, as was the case in
> > versions 15 and earlier.

> The buildfarm module assumes that no adjustments are necessary if the old
> and new versions are the same (e.g. HEAD to HEAD). And it never passes in a
> version like '16beta2'. It extracts the version number from the branch name,
> e.g. REL_16_STABLE => 16.

Hmm, OK, but I'm not testing the same versions -- I'm testing 16beta2 to
17devel.

> > I can fix this either by using DROP IF EXISTS in that stanza, or by
> > making AdjustUpgrade use 'version <= 15'.  Any opinions on which to
> > prefer?
> 
> The trouble is this could well break the next time someone puts in a test
> like this.

Hmm, I don't understand what you mean.

> Maybe we need to make AdjustUpgrade just look at the major version,
> something like:
> 
>    $old_version = PostgreSQL::Version->new($old_version->major);

It seems like that does work, but if we do that, then we also need to
change this line:

	if ($old_version lt '9.5')
to
	if ($old_version < '9.5')

otherwise you get some really mysterious failures about trying to drop
public.=>, which is in fact no longer accepted syntax since 9.5; and the
stringwise comparison returns the wrong value here.

TBH I'm getting a sense of discomfort with the idea of having developed
a Postgres-version-number Perl module, and in the only place where we
can use it, have to settle for numeric comparison instead.

-- 
Álvaro Herrera         PostgreSQL Developer  —  https://www.EnterpriseDB.com/
¡Ay, ay, ay!  Con lo mucho que yo lo quería (bis)
se fue de mi vera ... se fue para siempre, pa toíta ... pa toíta la vida
¡Ay Camarón! ¡Ay Camarón!                                (Paco de Lucía)