> The actual call I had tried was
> Payment.objects.filter(appliedpayment__invoice__location=loc).distinct().ag
> gregate(Sum('amount'))
> (where amount is a field on Payment). I could do
> AppliedPayment...aggregate(...), but unfortunately the AppliedPayment
> splits the 'amount' into several values (based on revenue type), which
> would mean doing several aggregate calls and summing them, which I've
> already done when it seemed appropriate (and I just discovered while
> writing this that aggregate can take more than one argument, but I
> don't know if that results in a single query).
Multiple aggregates within the same aggregate(), I'm 99% sure, are put
into a single query, at least if they're simple and not spanning
complex relationships themselves.
> For now, when I know
> there's generally going to be less than a dozen instances, I've just
> done the processing in python, which I'm sure will work fine.
>
> I was hoping for an elegant solution for when I know there's going to
> be several thousand plus instances (or hundreds of thousands after a
> year or two of deployment). So in the end, I guess I can work with it,
> but mostly I was hoping to find out whether the whole respecting
> distinct() thing could be made to happen.
Yeah, that's a tricky use case no matter what. I don't think there's a
way out of *something* doing some heavy lifting, whether it be python
or the db. But as I've seen mentioned many times (often by
Malcolm...where's a Malcolm bat-signal when you need one? I'd love to
hear his thoughts on this) the ORM isn't designed and can't be
expected to handle 100% of cases. This may indeed be a situation where
a simple extra() actually *is* the elegant solution.
> Dunno if it's worthwhile filing a ticket for it, or if there is one.
> Or maybe just a doc ticket for mentioning explicitly that aggregate
> ignores distinct.
Certainly agree with this.
Sorry I couldn't be more help!
Regards
Scott
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