Add support to update a JSONField with result from annotation

[Xavier Lesa]

I have a model with a JSONField and want to update in just one query like any other Field. Something like this:

    # one query update
    related_machinery = ActivityTracking.objects.filter(machinery=OuterRef('pk')).values('machinery')
    sub_total = related_machinery.annotate(Sum('measure_value')).values('measure_value__sum')
    avg_total = related_machinery.annotate(Avg('measure_value')).values('measure_value__avg')

    Machinery.objects.filter(id=machinery_id).update(
        measure_value=F('initial_measure_value') + sub_total,
        metrics=avg_total
    )

In example measure_value is a DecimalField and metrics is a JSONField. Also will be great if keys in JSONField was accessibles in update, like this:

    Machinery.objects.filter(id=instance.machinery_id).update(
        measure_value=F('initial_measure_value') + sub_total,
        metrics__average_measure_value=avg_total
    )

[Mariusz Felisiak]

Duplicate of #29112.