From 2d76b61dc2a45d5acda53736433a22a1b74e0514 Mon Sep 17 00:00:00 2001
From: Tim Graham <timograham@gmail.com>
Date: Thu, 23 Apr 2015 20:13:24 -0400
Subject: [PATCH] Fixed #24649 -- Allowed using Avg aggregate on non-numeric
field types.
---
django/db/backends/base/features.py | 3 +++
django/db/backends/oracle/features.py | 1 +
django/db/models/aggregates.py | 8 ++-----
docs/ref/models/querysets.txt | 13 ++++++++---
docs/releases/1.9.txt | 4 ++++
tests/aggregation/models.py | 1 +
tests/aggregation/tests.py | 31 +++++++++++++++++++++------
7 files changed, 46 insertions(+), 15 deletions(-)
diff --git a/django/db/backends/base/features.py b/django/db/backends/base/features.py
index d9463ddf19..e03a097a04 100644
--- a/django/db/backends/base/features.py
+++ b/django/db/backends/base/features.py
@@ -160,6 +160,9 @@ class BaseDatabaseFeatures(object):
# Support for the DISTINCT ON clause
can_distinct_on_fields = False
+ # Can the backend use an Avg aggregate on DurationField?
+ can_avg_on_durationfield = True
+
# Does the backend decide to commit before SAVEPOINT statements
# when autocommit is disabled? http://bugs.python.org/issue8145#msg109965
autocommits_when_autocommit_is_off = False
diff --git a/django/db/backends/oracle/features.py b/django/db/backends/oracle/features.py
index 0b152e612e..2a17bc5a8f 100644
--- a/django/db/backends/oracle/features.py
+++ b/django/db/backends/oracle/features.py
@@ -40,6 +40,7 @@ class DatabaseFeatures(BaseDatabaseFeatures):
uppercases_column_names = True
# select for update with limit can be achieved on Oracle, but not with the current backend.
supports_select_for_update_with_limit = False
+ can_avg_on_durationfield = False # Pending implementation (#24699).
def introspected_boolean_field_type(self, field=None, created_separately=False):
"""
diff --git a/django/db/models/aggregates.py b/django/db/models/aggregates.py
index b51fe5635a..2d7c43c90e 100644
--- a/django/db/models/aggregates.py
+++ b/django/db/models/aggregates.py
@@ -75,12 +75,8 @@ class Avg(Aggregate):
name = 'Avg'
def __init__(self, expression, **extra):
- super(Avg, self).__init__(expression, output_field=FloatField(), **extra)
-
- def convert_value(self, value, expression, connection, context):
- if value is None:
- return value
- return float(value)
+ output_field = extra.pop('output_field', FloatField())
+ super(Avg, self).__init__(expression, output_field=output_field, **extra)
class Count(Aggregate):
diff --git a/docs/ref/models/querysets.txt b/docs/ref/models/querysets.txt
index 3dc66f631a..d2cbc63203 100644
--- a/docs/ref/models/querysets.txt
+++ b/docs/ref/models/querysets.txt
@@ -2802,12 +2802,19 @@ by the aggregate.
Avg
~~~
-.. class:: Avg(expression, output_field=None, **extra)
+.. class:: Avg(expression, output_field=FloatField(), **extra)
- Returns the mean value of the given expression, which must be numeric.
+ Returns the mean value of the given expression, which must be numeric
+ unless you specify a different ``output_field``.
* Default alias: ``<field>__avg``
- * Return type: ``float``
+ * Return type: ``float`` (or the type of whatever ``output_field`` is
+ specified)
+
+ .. versionchanged:: 1.9
+
+ The ``output_field`` parameter was added to allow aggregating over
+ non-numeric columns, such as ``DurationField``.
Count
~~~~~
diff --git a/docs/releases/1.9.txt b/docs/releases/1.9.txt
index 525cf34630..21df59f051 100644
--- a/docs/releases/1.9.txt
+++ b/docs/releases/1.9.txt
@@ -200,6 +200,10 @@ Models
(such as :lookup:`exact`, :lookup:`gt`, :lookup:`lt`, etc.). For example:
``Entry.objects.filter(pub_date__month__gt=6)``.
+* You can specify the ``output_field`` parameter of the
+ :class:`~django.db.models.Avg` aggregate in order to aggregate over
+ non-numeric columns, such as ``DurationField``.
+
CSRF
^^^^
diff --git a/tests/aggregation/models.py b/tests/aggregation/models.py
index 0ca20def3e..de9dc5550c 100644
--- a/tests/aggregation/models.py
+++ b/tests/aggregation/models.py
@@ -17,6 +17,7 @@ class Author(models.Model):
class Publisher(models.Model):
name = models.CharField(max_length=255)
num_awards = models.IntegerField()
+ duration = models.DurationField(blank=True, null=True)
def __str__(self):
return self.name
diff --git a/tests/aggregation/tests.py b/tests/aggregation/tests.py
index 3e2bc2eb30..81152fd2ad 100644
--- a/tests/aggregation/tests.py
+++ b/tests/aggregation/tests.py
@@ -7,10 +7,10 @@ from decimal import Decimal
from django.core.exceptions import FieldError
from django.db import connection
from django.db.models import (
- F, Aggregate, Avg, Count, DecimalField, FloatField, Func, IntegerField,
- Max, Min, Sum, Value,
+ F, Aggregate, Avg, Count, DecimalField, DurationField, FloatField, Func,
+ IntegerField, Max, Min, Sum, Value,
)
-from django.test import TestCase, ignore_warnings
+from django.test import TestCase, ignore_warnings, skipUnlessDBFeature
from django.test.utils import Approximate, CaptureQueriesContext
from django.utils import six, timezone
from django.utils.deprecation import RemovedInDjango20Warning
@@ -40,8 +40,8 @@ class AggregateTestCase(TestCase):
cls.a8.friends.add(cls.a9)
cls.a9.friends.add(cls.a8)
- cls.p1 = Publisher.objects.create(name='Apress', num_awards=3)
- cls.p2 = Publisher.objects.create(name='Sams', num_awards=1)
+ cls.p1 = Publisher.objects.create(name='Apress', num_awards=3, duration=datetime.timedelta(days=1))
+ cls.p2 = Publisher.objects.create(name='Sams', num_awards=1, duration=datetime.timedelta(days=2))
cls.p3 = Publisher.objects.create(name='Prentice Hall', num_awards=7)
cls.p4 = Publisher.objects.create(name='Morgan Kaufmann', num_awards=9)
cls.p5 = Publisher.objects.create(name="Jonno's House of Books", num_awards=0)
@@ -441,6 +441,13 @@ class AggregateTestCase(TestCase):
vals = Book.objects.annotate(num_authors=Count("authors__id")).aggregate(Avg("num_authors"))
self.assertEqual(vals, {"num_authors__avg": Approximate(1.66, places=1)})
+ @skipUnlessDBFeature('can_avg_on_durationfield')
+ def test_avg_duration_field(self):
+ self.assertEqual(
+ Publisher.objects.aggregate(Avg('duration', output_field=DurationField())),
+ {'duration__avg': datetime.timedelta(1, 43200)} # 1.5 days
+ )
+
def test_sum_distinct_aggregate(self):
"""
Sum on a distict() QuerySet should aggregate only the distinct items.
@@ -620,7 +627,14 @@ class AggregateTestCase(TestCase):
self.assertEqual(vals, {"rating__avg": 4.25})
def test_even_more_aggregate(self):
- publishers = Publisher.objects.annotate(earliest_book=Min("book__pubdate")).exclude(earliest_book=None).order_by("earliest_book").values()
+ publishers = Publisher.objects.annotate(
+ earliest_book=Min("book__pubdate"),
+ ).exclude(earliest_book=None).order_by("earliest_book").values(
+ 'earliest_book',
+ 'num_awards',
+ 'id',
+ 'name',
+ )
self.assertEqual(
list(publishers), [
{
@@ -836,6 +850,11 @@ class AggregateTestCase(TestCase):
self.assertEqual(a2, {'av_age': 37})
self.assertEqual(a3, {'av_age': Approximate(37.4, places=1)})
+ def test_avg_decimal_field(self):
+ v = Book.objects.filter(rating=4).aggregate(avg_price=(Avg('price')))['avg_price']
+ self.assertIsInstance(v, float)
+ self.assertEqual(v, Approximate(47.39, places=2))
+
def test_order_of_precedence(self):
p1 = Book.objects.filter(rating=4).aggregate(avg_price=(Avg('price') + 2) * 3)
self.assertEqual(p1, {'avg_price': Approximate(148.18, places=2)})