#28553: Querysets: annotate() columns are forced into a certain position which
may
disrupt union()
-------------------------------------+-------------------------------------
Reporter: David Sanders | Owner: nobody
Type: | Status: new
Cleanup/optimization |
Component: Database layer | Version: 1.11
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Comment (by Flávio Juvenal):
I've stumbled upon a case in production where this limitation prevents me
for making a useful query. I've been able to create a test to reproduce
this problem.
It works with sqlite but fails with postgres.
Add this test to {{{tests/queries/test_qs_combinators.py}}}:
{{{
#!python
from django.db.models import F, IntegerField, TextField, Value
def test_union_with_two_annotated_values_on_different_models(self):
qs1 = Number.objects.annotate(
text_annotation=Value('Foo', TextField())
).values('text_annotation', 'num')
qs2 = ReservedName.objects.annotate(
int_annotation=Value(1, IntegerField()),
).values('name', 'int_annotation')
self.assertEqual(qs1.union(qs2).count(), 10)
}}}
In current master (`78f8b80f9b215e50618375adce4c97795dabbb84`), running
{{{./runtests.py --parallel=1 --settings=tests.test_postgres
queries.test_qs_combinators.QuerySetSetOperationTests.test_union_with_two_annotated_values_on_different_models}}}
fails:
{{{
Testing against Django installed in 'django/django'
Creating test database for alias 'default'...
Creating test database for alias 'other'...
System check identified no issues (1 silenced).
E
======================================================================
ERROR: test_union_with_two_annotated_values_on_different_models
(queries.test_qs_combinators.QuerySetSetOperationTests)
----------------------------------------------------------------------
Traceback (most recent call last):
File "django/django/db/backends/utils.py", line 85, in _execute
return self.cursor.execute(sql, params)
psycopg2.ProgrammingError: UNION types integer and character varying
cannot be matched
LINE 1: ..._annotation" FROM "queries_number") UNION (SELECT "queries_r...
^
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "django/tests/queries/test_qs_combinators.py", line 140, in
test_union_with_two_annotated_values_on_different_models
self.assertEqual(qs1.union(qs2).count(), 10)
File "django/django/db/models/query.py", line 382, in count
return self.query.get_count(using=self.db)
File "django/django/db/models/sql/query.py", line 494, in get_count
number = obj.get_aggregation(using, ['__count'])['__count']
File "django/django/db/models/sql/query.py", line 479, in
get_aggregation
result = compiler.execute_sql(SINGLE)
File "django/django/db/models/sql/compiler.py", line 1054, in
execute_sql
cursor.execute(sql, params)
File "django/django/db/backends/utils.py", line 68, in execute
return self._execute_with_wrappers(sql, params, many=False,
executor=self._execute)
File "django/django/db/backends/utils.py", line 77, in
_execute_with_wrappers
return executor(sql, params, many, context)
File "django/django/db/backends/utils.py", line 85, in _execute
return self.cursor.execute(sql, params)
File "django/django/db/utils.py", line 89, in __exit__
raise dj_exc_value.with_traceback(traceback) from exc_value
File "django/django/db/backends/utils.py", line 85, in _execute
return self.cursor.execute(sql, params)
django.db.utils.ProgrammingError: UNION types integer and character
varying cannot be matched
LINE 1: ..._annotation" FROM "queries_number") UNION (SELECT "queries_r...
^
----------------------------------------------------------------------
Ran 1 test in 0.007s
FAILED (errors=1)
Destroying test database for alias 'default'...
Destroying test database for alias 'other'...
}}}
My {{{tests/test_postgres.py}}} is:
{{{
DATABASES = {
'default': {
'ENGINE': 'django.db.backends.postgresql_psycopg2',
'NAME': 'django-test',
'HOST': '127.0.0.1',
},
'other': {
'ENGINE': 'django.db.backends.postgresql_psycopg2',
'NAME': 'django-test-other',
}
}
SECRET_KEY = "django_tests_secret_key"
# Use a fast hasher to speed up tests.
PASSWORD_HASHERS = [
'django.contrib.auth.hashers.MD5PasswordHasher',
]
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/28553#comment:3>
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