Consider library authors:
class WindowFunction(Func):
def as_sql(self, compiler, connection): # standard implementation
return compiler.compile(self.expressions)
def as_sqlite(self, compiler, connection): # unsupported first party
backend
raise NotSupportedException("WindowFunction not supported with
SQLite")
def as_mssql(self, compiler, connection): # third party backend
self.function = "SlightlyDifferentFunctionName"
return self.as_sql(compiler, connection)
I think the as_{vendor} makes all backends equal - both core and non-core
backends. We all use the same API. We can anticipate some of the backends
that will use a particular function, but make it possible and easy for
other backends to jump onboard. This is in contrast to the existing process
of providing implementations directly inside the backend
(DatabaseOperations). But this is a part that I'm struggling with. Should
we push Function implementations down into DatabaseOperations, or continue
with the as_vendor? I really like the as_vendor implementation for
Expressions since there will be a large number of Expressions which will
work across all backends with the default as_sql(), but there is an easy
extension point. I see libraries providing a larger set of expressions than
django does.
I don't like the setattr(Expression.. ) syntax for providing
implementations though. I'd probably prefer a .register(vendor, function).
Josh
On Wednesday, 18 June 2014 23:31:39 UTC+10, Aymeric Augustin wrote:
>
> 2014-06-18 15:19 GMT+02:00 Josh Smeaton <josh.s...@gmail.com <javascript:>
> >:
>
>> At the moment the API sanctions monkey patching by providing the
>> as_vendor() method
>>
>
> Yes, I'm not happy with the as_<vendor>() API either, because it creates a
> large asymmetry between the core and non-core backends.
>
> --
> Aymeric.
>
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