[Mediawiki-l] MediaWiki unit testing and non-MySQL databases

[Brion Vibber]

Hey all --

I've got a stack of issues discussed during the last couple months'
conferences and hackathons to raise, so there may be a few more manifestos
on the way. But don't worry, this one will be short!


I had a great chat at the New Orleans hackathon with D J Bauch who's been
working on maintaining MediaWiki's MS SQL Server support, and also had a
very useful email chat a couple weeks back with Freakalowsky who's put a lot
of work into MediaWiki's Oracle support.

Long story short: though traditionally MediaWiki developers have put very
little work on our own into maintaining non-MySQL compatibility, there's
still lots of folks interested in running on them... AND THEY ACTUALLY
MOSTLY WORK!

At this point I think it's a bit crazy of us to keep on marginalizing that
code; some folks running their own instances will need or want or prefer (or
be forced by office IT) to run on some "funny" database, and we shouldn't
stand in their way. More importantly, keeping things working with multiple
DB backends helps us to keep our code cleaner, and reduces our own hard
dependencies on a particular product line.


There are two main impediments to keeping code working on non-MySQL
platforms:
* lazy code breakages -- us MySQL-natives accidentally use MySQL-isms that
break queries on other platforms
* lazy schema updates -- us MySQL-natives add new schema updates into the
system but only implement them for MySQL

The first could often be helped simply by having automated testing run to
make sure that relevant code paths get exercised. Often there's just a
function that's used, or lazy use of LIMIT/OFFSET, or GROUP BY in a form
that other databases are pickier about. Just flagging them from the testing
can often be enough to make it easy to fix.

The second is a bit harder, but again testing can help flag that something
needs to be updated so it doesn't wait until too late for the next release,
or something.


I'd like for everybody who's working on MediaWiki on non-MySQL databases to
make sure that the phpunit test suite can run on your favorite platform, so
we can see about getting them set up in our regular reports on
http://integration.mediawiki.org/ci/

Green bars are your friend! :)

-- brion