#30188: Aggregate annotation, Case() - When(): AssertionError No exception
message
supplied
-------------------------------------+-------------------------------------
Reporter: Lukas | Owner: nobody
Klement |
Type: Bug | Status: new
Component: Database | Version: 2.1
layer (models, ORM) | Keywords: query, aggregate,
Severity: Normal | case/when
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
-------------------------------------+-------------------------------------
Aggregating annotations works for simple Sum, Count, etc. operations, but
fails when the Sum() contains a Case() When() operation.
Example:
Objective: sum the number of None values for the annotated field
field_name across a queryset.
{{{
field_name = <name of annotated field>
missing_data_agg=Sum(
Case(
When(**{field_name: None}, then=Value(1)),
default=Value(0),
output_field=IntegerField()
)
)
}}}
Expected behaviour: calling
queryset.aggregate(missing_data=missing_data_agg) returns a dict
{'missing_data': <value>}
Actual behaviour: AssertionError No exception message supplied is
returned.
When field_name is set to a field that exists on the model of the
queryset, the aggregation works. When field_name is set to a field that is
neither in the model of the queryset, nor has it been annotated to the
queryset, the exception returned is as expected: Cannot resolve keyword
<name of the non existing field> into field . Choices are: <list of model
and annotated fields. In this list, the field_name that has been annotated
to the queryset is shown -> hence it should work, hence I assume this is a
Django bug.
Stacktrace:
{{{
<Line with the .aggregate(...)>
return query.get_aggregation(self.db, kwargs) ...
/Users/{{path}}/lib/python3.6/site-packages/django/db/models/sql/query.py
in get_aggregation
expression, col_cnt =
inner_query.rewrite_cols(expression, col_cnt) ...
/Users/{{path}}/lib/python3.6/site-packages/django/db/models/sql/query.py
in rewrite_cols
new_expr, col_cnt = self.rewrite_cols(expr, col_cnt) ...
/Users/{{path}}/lib/python3.6/site-packages/django/db/models/sql/query.py
in rewrite_cols
new_expr, col_cnt = self.rewrite_cols(expr, col_cnt) ...
/Users/{{path}}/lib/python3.6/site-packages/django/db/models/sql/query.py
in rewrite_cols
new_expr, col_cnt = self.rewrite_cols(expr, col_cnt) ...
/Users/{{path}}/lib/python3.6/site-packages/django/db/models/sql/query.py
in rewrite_cols
new_expr, col_cnt = self.rewrite_cols(expr, col_cnt) ...
/Users/{{path}}/lib/python3.6/site-packages/django/db/models/sql/query.py
in rewrite_cols
new_expr, col_cnt = self.rewrite_cols(expr, col_cnt) ...
/Users/{{path}}/lib/python3.6/site-packages/django/db/models/sql/query.py
in rewrite_cols
new_expr, col_cnt = self.rewrite_cols(expr, col_cnt) ...
/Users/{{path}}/lib/python3.6/site-packages/django/db/models/sql/query.py
in rewrite_cols
annotation.set_source_expressions(new_exprs) ...
/Users/{{path}}/lib/python3.6/site-
packages/django/db/models/expressions.py in set_source_expressions
assert not exprs
}}}
The database is a PostgreSQL database, the Django version is 2.1.7, the
Python version is 3.6.4.
--
Ticket URL: <https://code.djangoproject.com/ticket/30188>
Django <https://code.djangoproject.com/>
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