Re: multi-install PostgresNode fails with older postgres versions

On 4/19/21 8:32 AM, Michael Paquier wrote:
> On Mon, Apr 19, 2021 at 08:11:01AM -0400, Andrew Dunstan wrote:
>> As far as I know, without any compatibility changes the module is fully
>> compatible with releases 13 and 12, and with releases 11 and 10 so long
>> as you don't want a standby, and with releases 9.6 and 9.5 if you also
>> don't want a backup. That makes it suitable for a lot of testing without
>> any attempt at version compatibility.
>>
>> We can revisit compatibility further in the next release.
> Agreed, and I am not convinced that there is any strong need for any
> of that in the close future either, as long as there are no
> ground-breaking compatibility changes.
>
> How far does the buildfarm test pg_upgrade? One thing that I
> personally care about here is the possibility to make pg_upgrade's
> test.sh become a TAP test. However, I am also pretty sure that we
> could apply some local changes to the TAP test of pg_upgrade itself to
> not require any wide changes to PostgresNode.pm either to make the
> central logic as simple as possible with all the stable branches still
> supported or even older ones. Having compatibility for free down to
> 12 is nice enough IMO for most of the core logic, and pg_upgrade would
> also work just fine down to 9.5 without any extra changes because we
> don't care there about standbys or backups.

The buildfarm tests self-targetted pg_upgrade by calling the builtin
tests (make check / vcregress.pl upgradecheck).

However, for cross version testing the regime is quite different. The
cross version module doesn't ever construct a repo. Rather, it tries to
upgrade a repo saved from a prior run. So all it does is some
adjustments for things that have changed between releases and then calls
pg_upgrade. See
<https://github.com/PGBuildFarm/client-code/blob/master/PGBuild/Modules/TestUpgradeXversion.pm>

Note that we currently test upgrades down to 9.2 on crake. However, now
I have some working binaries for really old releases I might extend that
all the way back to 8.4 at some stage. pg_upgrade and pg_dump/pg_restore
testing are the major use cases I can see for backwards compatibility -
pg_dump is still supposed to be able to go back into the dim dark ages,
which is why I built the old binaries all the way back to 7.2.

....

It's just occurred to me that a much nicer way of doing this
PostgresNode stuff would be to have a function that instead of appending
to the config file would adjust it. Then we wouldn't need all those
little settings functions to be overridden - the subclasses could just
post-process the  config files. I'm going to try that and see what I can
come up with. I think it will look heaps nicer.

cheers

andrew

--
Andrew Dunstan
EDB: https://www.enterprisedb.com

--
--
Andrew Dunstan
EDB: https://www.enterprisedb.com