Ok, can we have
is_adult = models.DBCalculatedField(ExpressionWrapper(Q(age__gt=18),
output_field=BooleanField()))
Any query for model with this field will be automatically annotated with
.annotate(is_adult =ExpressionWrapper(Q(age__gt=18),
output_field=BooleanField()))
We may use F fields also, something like
full_name = models.DBCalculatedField(ExpressionWrapper(F('first_name') +
F('last_name'), output_field=CharField()))
We may simplify it to
is_adult = models.DBCalculatedField(expr=Q(age__gt=18),
output_field=BooleanField()))
It will work for any object, created from database.
For local computation we may give user ability to provide lambda or
decorate method (as in your example).
After it, I can create my own mixin as *third party lib* to patch model
with DBCalculatedField and calcuate its expression locally.
class Customer(models.Model, UnsafeCalculateDbLocallyMixin):
age = models.IntegerField()
is_adult = models.DBCalculatedField(expr=Q(age__gt=18),
output_field=BooleanField()))
Ilya.
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