[Answered ]-Group by with related_name relation using Prefetch

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Thanks to @PTomasz comment, I’ve added Window expression to my query.

So the final query looks like this:

groups = Group.objects.prefetch_related(
    Prefetch("facts",
             queryset=Facts.objects.annotate(
                 sum_weight=Window(
                     expression=Sum('weight'), 
                     partition_by=[F('date')],
                     order_by=OrderBy(F('date'))))
             .distinct("date"))
)

Without .distinct("date") objects were still duplicating, but with right sum_weight (both had 1500).

With it everyting is good.

👤COSHW

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