#24764: Using 'startswith' field lookup with F objects causes AttributeError
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Reporter: Ernest0x | Owner: nobody
Type: Bug | Status: new
Component: Database layer (models, ORM) | Version: 1.7
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 0 | UI/UX: 0
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In Django 1.7.8, when using "startswith" field lookup with F objects in
the same query, the following AttributeError exception is raised:
{{{
>>> objects = MyObject.objects.filter(name__startswith=F('description'))
>>> objects
Traceback (most recent call last):
File "<console>", line 1, in <module>
File "/path/to/virtualenv/lib/python3.4/site-
packages/django/db/models/query.py", line 116, in __repr__
data = list(self[:REPR_OUTPUT_SIZE + 1])
File "/path/to/virtualenv/lib/python3.4/site-
packages/django/db/models/query.py", line 141, in __iter__
self._fetch_all()
File "/path/to/virtualenv/lib/python3.4/site-
packages/django/db/models/query.py", line 966, in _fetch_all
self._result_cache = list(self.iterator())
File "/path/to/virtualenv/lib/python3.4/site-
packages/django/db/models/query.py", line 265, in iterator
for row in compiler.results_iter():
File "/path/to/virtualenv/lib/python3.4/site-
packages/django/db/models/sql/compiler.py", line 701, in results_iter
for rows in self.execute_sql(MULTI):
File "/path/to/virtualenv/lib/python3.4/site-
packages/django/db/models/sql/compiler.py", line 776, in execute_sql
sql, params = self.as_sql()
File "/path/to/virtualenv/lib/python3.4/site-
packages/django/db/models/sql/compiler.py", line 110, in as_sql
where, w_params = self.compile(self.query.where)
File "/path/to/virtualenv/lib/python3.4/site-
packages/django/db/models/sql/compiler.py", line 81, in compile
return node.as_sql(self, self.connection)
File "/path/to/virtualenv/lib/python3.4/site-
packages/django/db/models/sql/where.py", line 106, in as_sql
sql, params = qn.compile(child)
File "/path/to/virtualenv/lib/python3.4/site-
packages/django/db/models/sql/compiler.py", line 81, in compile
return node.as_sql(self, self.connection)
File "/path/to/virtualenv/lib/python3.4/site-
packages/django/db/models/lookups.py", line 152, in as_sql
rhs_sql = self.get_rhs_op(connection, rhs_sql)
File "/path/to/virtualenv/lib/python3.4/site-
packages/django/db/models/lookups.py", line 258, in get_rhs_op
return connection.pattern_ops[self.lookup_name] % rhs
AttributeError: 'DatabaseWrapper' object has no attribute 'pattern_ops'
}}}
The following (without the 'startswith' field lookup), however, works:
{{{
>>> objects = MyObject.objects.filter(name=F('description'))
>>> objects
[...]
}}}
Interestingly, Django 1.8 does not have this bug.
--
Ticket URL: <https://code.djangoproject.com/ticket/24764>
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