Hi Carl,
On Wed, 18 Jun 2014, Carl Meyer wrote:
On 06/18/2014 02:59 PM, Aymeric Augustin wrote:
2014-06-18 19:18 GMT+02:00 Carl Meyer <c...@oddbird.net
<mailto:c...@oddbird.net>>:
If you need a Function in your project (whether provided by Django or
by a third-party library), and the Function doesn't natively support
the database backend you're using, you can simply subclass it, add the
appropriate as_vendor method, and use your subclass.
I was thinking about third-party database backends. How are they
expected to ship customised implementations of Functions included in
Django?
Yes, I wasn't thinking about this case in my first mail, and I agree
that this is a serious problem for the pure as_vendor() approach; it's
not acceptable IMO to expect third-party database backends to
monkeypatch their as_vendor() methods onto the built-in Function classes.
I think database backends should have a hook to override the SQL
implementation of any given Function. I don't think this needs to imply
pushing the default implementation of all Functions down into the
database backend (that just makes life unnecessarily difficult for
third-party Functions).
Why does it even need a hook or monkey-patching? Why not pass the
expression tree to the SQL backend (as the most natural format for
programmatically parsing), for it to render out in backend-specific SQL as
it sees fit? Perhaps relying in inherited base methods in most cases, and
overriding a few methods where that backend needs to render a particular
feature differently?
Cheers, Chris.
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