#34564: returning None instead of zero in Count annotation
-------------------------------------+-------------------------------------
Reporter: Amin Aminian | Owner: Amin
| Aminian
Type: Bug | Status: assigned
Component: Database layer | Version: 4.2
(models, ORM) |
Severity: Normal | Resolution:
Keywords: count, orm, | Triage Stage: Accepted
annotate |
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Comment (by Amin Aminian):
Thanks Simon for explaining `empty_result_set_value` usage.
So, as far as I understood, if the query is going to return None, we
return `empty_result_set_value` instead, without running the query. Right
? If it's right, there is still something that I'm missing.
My point is, assume that we have a query that the compiler does not know
that it is going to return None (normal queries like
`objects.annotate(count=Count("..."))`). In this case, the query is going
to be run, and the result would be fetched. Now why we can't use
`empty_result_set_value` in case of result is None ?
What I am saying is a code like this:
{{{
class BaseExpression:
...
@cached_property
def convert_value(self):
field = self.output_field
internal_type = field.get_internal_type()
...
elif internal_type.endswith("IntegerField"):
return (
lambda value, expression, connection:
self.empty_result_set_value # instead of None
if value is None
else int(value)
)
...
return self._convert_value_noop
}}}
And about Python time conversions, we are already running this
`convert_property` for each row.
--
Ticket URL: <https://code.djangoproject.com/ticket/34564#comment:9>
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