#27123: prefetch_related return mistaken result
-------------------------------------+-------------------------------------
Reporter: mostafa | Owner: nobody
Type: Bug | Status: new
Component: Database layer | Version: 1.9
(models, ORM) |
Severity: Normal | Resolution:
Keywords: prefetch_related, | Triage Stage: Accepted
ORM, postgresql |
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Changes (by François Freitag):
* cc: mail@… (added)
Comment:
Hi,
I fail to reproduce this issue. The code given by Baptiste leads to a test
fail, but it's only a matter of ordering.
The test below passes (I've commented the changes):
{{{#!python
# tests.py
def test_reproduction(self):
my_teams = GlobalTeam.objects.prefetch_related(
'user_profiles',
).annotate(
user_cnt=(
Count('user_profiles', distinct=True) + 1 # Added the "+
1"
),
).distinct()
self.assertEqual(len(my_teams), 2)
self.assertQuerysetEqual(
my_teams[1].user_profiles.all(), # Changed my_teams[0] to
my_teams[1]
['<UserProfile: a>', '<UserProfile: b>', '<UserProfile: c>'],
ordered=False,
)
self.assertQuerysetEqual(
my_teams[0].user_profiles.all(), # Change my_teams[1] to
my_teams[0]
['<UserProfile: d>'],
ordered=False,
)
evaluated = list(my_teams)
self.assertQuerysetEqual(
evaluated[1].user_profiles.all(), # Changed evaluated[0] to
evaluated[1]
['<UserProfile: a>', '<UserProfile: b>', '<UserProfile: c>'],
ordered=False,
)
self.assertQuerysetEqual(
evaluated[0].user_profiles.all(), # Changed evaluated[1] to
evaluated[0]
['<UserProfile: d>'],
ordered=False,
)
}}}
I cannot reproduce the original issue:
{{{#!python
my_teams = GlobalTeam.objects.filter(Q(team_admin__user=user) |
Q(user_profiles__user=user)).select_related(
'team_admin',
'team_admin__user'
).prefetch_related(
'user_profiles',
'user_profiles__user',
).annotate(
user_cnt=(
Count('user_profiles', distinct=True) +
1
),
).distinct()
# Breakpoint...
(Pdb) print(my_teams[0].user_profiles.all())
[<UserProfile: d>]
(Pdb) print(my_teams[1].user_profiles.all())
[<UserProfile: a>, <UserProfile: b>, <UserProfile: c>]
(Pdb) for team in my_teams: print(team.user_profiles.all())
[<UserProfile: d>]
[<UserProfile: a>, <UserProfile: b>, <UserProfile: c>]
(Pdb) my_teams[0].user_profiles.all()
[<UserProfile: d>]
}}}
I'm using django 1.9.9 and postgresql 9.3.14.
I could not reproduce it on master as well (with postgresql 9.5.4).
Have I missed something?
--
Ticket URL: <https://code.djangoproject.com/ticket/27123#comment:4>
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