mirror of
https://github.com/django/django.git
synced 2024-12-26 11:06:07 +00:00
466198c4d9
git-svn-id: http://code.djangoproject.com/svn/django/trunk@10092 bcc190cf-cafb-0310-a4f2-bffc1f526a37
103 lines
3.0 KiB
Python
103 lines
3.0 KiB
Python
"""
|
|
Tests for defer() and only().
|
|
"""
|
|
|
|
from django.db import models
|
|
from django.db.models.query_utils import DeferredAttribute
|
|
|
|
class Secondary(models.Model):
|
|
first = models.CharField(max_length=50)
|
|
second = models.CharField(max_length=50)
|
|
|
|
class Primary(models.Model):
|
|
name = models.CharField(max_length=50)
|
|
value = models.CharField(max_length=50)
|
|
related = models.ForeignKey(Secondary)
|
|
|
|
def __unicode__(self):
|
|
return self.name
|
|
|
|
def count_delayed_fields(obj, debug=False):
|
|
"""
|
|
Returns the number of delayed attributes on the given model instance.
|
|
"""
|
|
count = 0
|
|
for field in obj._meta.fields:
|
|
if isinstance(obj.__class__.__dict__.get(field.attname),
|
|
DeferredAttribute):
|
|
if debug:
|
|
print field.name, field.attname
|
|
count += 1
|
|
return count
|
|
|
|
|
|
__test__ = {"API_TEST": """
|
|
To all outward appearances, instances with deferred fields look the same as
|
|
normal instances when we examine attribut values. Therefore we test for the
|
|
number of deferred fields on returned instances (by poking at the internals),
|
|
as a way to observe what is going on.
|
|
|
|
>>> s1 = Secondary.objects.create(first="x1", second="y1")
|
|
>>> p1 = Primary.objects.create(name="p1", value="xx", related=s1)
|
|
|
|
>>> qs = Primary.objects.all()
|
|
|
|
>>> count_delayed_fields(qs.defer('name')[0])
|
|
1
|
|
>>> count_delayed_fields(qs.only('name')[0])
|
|
2
|
|
>>> count_delayed_fields(qs.defer('related__first')[0])
|
|
0
|
|
>>> obj = qs.select_related().only('related__first')[0]
|
|
>>> count_delayed_fields(obj)
|
|
2
|
|
>>> obj.related_id == s1.pk
|
|
True
|
|
>>> count_delayed_fields(qs.defer('name').extra(select={'a': 1})[0])
|
|
1
|
|
>>> count_delayed_fields(qs.extra(select={'a': 1}).defer('name')[0])
|
|
1
|
|
>>> count_delayed_fields(qs.defer('name').defer('value')[0])
|
|
2
|
|
>>> count_delayed_fields(qs.only('name').only('value')[0])
|
|
2
|
|
>>> count_delayed_fields(qs.only('name').defer('value')[0])
|
|
2
|
|
>>> count_delayed_fields(qs.only('name', 'value').defer('value')[0])
|
|
2
|
|
>>> count_delayed_fields(qs.defer('name').only('value')[0])
|
|
2
|
|
>>> obj = qs.only()[0]
|
|
>>> count_delayed_fields(qs.defer(None)[0])
|
|
0
|
|
>>> count_delayed_fields(qs.only('name').defer(None)[0])
|
|
0
|
|
|
|
User values() won't defer anything (you get the full list of dictionaries
|
|
back), but it still works.
|
|
>>> qs.defer('name').values()[0] == {'id': p1.id, 'name': u'p1', 'value': 'xx', 'related_id': s1.id}
|
|
True
|
|
>>> qs.only('name').values()[0] == {'id': p1.id, 'name': u'p1', 'value': 'xx', 'related_id': s1.id}
|
|
True
|
|
|
|
Using defer() and only() with get() is also valid.
|
|
>>> count_delayed_fields(qs.defer('name').get(pk=p1.pk))
|
|
1
|
|
>>> count_delayed_fields(qs.only('name').get(pk=p1.pk))
|
|
2
|
|
|
|
# KNOWN NOT TO WORK: >>> count_delayed_fields(qs.only('name').select_related('related')[0])
|
|
# KNOWN NOT TO WORK >>> count_delayed_fields(qs.defer('related').select_related('related')[0])
|
|
|
|
# Saving models with deferred fields is possible (but inefficient, since every
|
|
# field has to be retrieved first).
|
|
|
|
>>> obj = Primary.objects.defer("value").get(name="p1")
|
|
>>> obj.name = "a new name"
|
|
>>> obj.save()
|
|
>>> Primary.objects.all()
|
|
[<Primary: a new name>]
|
|
|
|
|
|
"""}
|