mirrors/django
1
0
Fork 0
mirror of https://github.com/django/django.git synced 2025-08-22 03:24:21 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions 4

Refs #26430 -- Re-introduced empty aggregation optimization.

Browse source 
The introduction of the Expression.empty_aggregate_value interface
allows the compilation stage to enable the EmptyResultSet optimization
if all the aggregates expressions implement it.

This also removes unnecessary RegrCount/Count.convert_value() methods.
Disabling the empty result set aggregation optimization when it wasn't
appropriate prevented None returned for a Count aggregation value.

Thanks Nick Pope for the review.
This commit is contained in:
Simon Charette 2021-05-21 22:32:16 -04:00 • committed by Mariusz Felisiak
parent f3112fde98
commit 9f3cce172f
8 changed files with 101 additions and 34 deletions
Download patch file Download diff file Expand all files Collapse all files

5
django/db/models/expressions.py
View file

@ -153,6 +153,7 @@ class BaseExpression:
# aggregate specific fields
is_summary = False
_output_field_resolved_to_none = False
empty_aggregate_value = NotImplemented
# Can the expression be used in a WHERE clause?
filterable = True
# Can the expression can be used as a source expression in Window?
@ -795,6 +796,10 @@ class Value(SQLiteNumericMixin, Expression):
if isinstance(self.value, UUID):
return fields.UUIDField()
@property
def empty_aggregate_value(self):
return self.value
class RawSQL(Expression):
def __init__(self, sql, params, output_field=None):