Hello Daniel,
It's hard to tell was causes the exception without digging a bit more but
based on your mention of multiple sums I assume you are trying to work
around the cross join of multiple table annotations?
I understand you simplified your query but from what I can see right now
it can be expressed as
commens_count = Comment.objects.annotate(
votes_count=Count('votes', filter=votes_filter),
).filter(
votes_count__gte=4
).count()
That should result in
SELECT COUNT(*) FROM (
SELECT 1
FROM comment
LEFT OUTER JOIN vote ON (vote.comment_id = comment.id)
GROUP BY comment.id
HAVING COUNT(*) FILTER (WHERE ...) > 4
)
There's tickets tracking adding subquery support to aggregate functions but
using subqueries doesn't seem to be necessary here?
Cheers,
Simon
Le mercredi 5 décembre 2018 19:16:30 UTC-5, Daniel Gilge a écrit :
>
> Hi,
>
> I think I've found a bug. But I'm not sure and I never opened a ticket for
> Django before. So, I first wanted to ask here.
>
> I'm using Django 2.0 and this doesn't work:
>
> subquery = Subquery(
> Vote.objects
> .filter(comment=OuterRef('pk'))
> .values('value')[:1]
> )
>
> Comment.objects.annotate(vote=subquery).aggregate(
> count=Count('vote', filter=Q(vote__gte=4)),
> )
>
> It results in a quite useless AssertionError:
>
> django/db/models/expressions.py
>
>
> 168 169 def set_source_expressions(self, exprs):--> 170
> assert len(exprs) == 0 171 172 def _parse_expressions(self,
> *expressions):
> AssertionError:
>
>
>
> Vars:
> exprs
>
> [Ref(__col8, Col(U0, myapp.Vote.comment))]
>
> self
>
> <django.db.models.expressions.Subquery object at 0x1080077b8>
>
>
>
> It probably doesn't make sense because I simplified it. Why I'm using
> subqueries is that I have several sums involved in the query:
>
> subquery = Subquery(
> Vote.objects
> .filter(comment=OuterRef('pk'))
> .values('comment_id')
> .annotate(sum=Sum('value', filter=Q(**filter_fields)))
> .values('sum')[:1]
> )
>
> However, what I had to remove is a filter statement and then it works:
>
> Comment.objects.annotate(vote=subquery).aggregate(
> count=Count('vote'),
> )
>
> Any advice appreciated!
>
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