only running distinct on one-to-many filters (fixes #26)

HISTORY.rst

@@ -3,6 +3,13 @@
 History
 -------
 
+0.3.10 (2018-11-14)
+~~~~~~~~~~~~~~~~~~
+
+* Only running ``distinct`` on queryset when one of filters is on one-to-many relation.
+  This should help with performance.
+  See `#26 <https://github.com/miki725/django-url-filter/issues/26>`_.
+
 0.3.9 (2018-11-12)
 ~~~~~~~~~~~~~~~~~~
 

tests/backends/test_django.py

@@ -70,17 +70,32 @@ def test_filter(self):
         qs = mock.Mock()
 
         backend = DjangoFilterBackend(qs)
+        backend.model = Place
         backend.bind([
             FilterSpec(['name'], 'exact', 'value', False),
             FilterSpec(['address'], 'contains', 'value', True),
         ])
 
         result = backend.filter()
 
-        assert result == qs.filter.return_value.exclude.return_value.distinct.return_value
+        assert result == qs.filter.return_value.exclude.return_value
         qs.filter.assert_called_once_with(name__exact='value')
         qs.filter.return_value.exclude.assert_called_once_with(address__contains='value')
 
+    def test_filter_to_many(self):
+        qs = mock.Mock()
+
+        backend = DjangoFilterBackend(qs)
+        backend.model = Place
+        backend.bind([
+            FilterSpec(['restaurant', 'waiter', 'name'], 'exact', 'value', False),
+        ])
+
+        result = backend.filter()
+
+        assert result == qs.filter.return_value.distinct.return_value
+        qs.filter.assert_called_once_with(restaurant__waiter__name__exact='value')
+
     def test_filter_callable_specs(self):
         qs = mock.Mock()
 
@@ -93,5 +108,5 @@ def foo(queryset, spec):
 
         result = backend.filter()
 
-        assert result == qs.distinct.return_value.filter.return_value
-        qs.distinct.return_value.filter.assert_called_once_with(spec)
+        assert result == qs.filter.return_value
+        qs.filter.assert_called_once_with(spec)

tox.ini

@@ -1,12 +1,13 @@
 [tox]
 envlist =
-    {py27,py36,pypy,pypy3}-django{18,11}
-    {py36,pypy3}-django20
+    {py27,py36,py37,pypy,pypy3}-django{18,11}
+    {py36,py37,pypy3}-django{20,latest}
 
 [testenv]
 basepython =
     py27: python2.7
     py36: python3.6
+    py37: python3.7
     pypy: pypy
     pypy3: pypy3
 setenv =
@@ -20,6 +21,7 @@ deps =
     django18: djangorestframework<3.7
     django11: django<2
     django20: django<2.1
+    djangolatest: django
 whitelist_externals =
     make
 

url_filter/__init__.py

@@ -4,4 +4,4 @@
 
 __author__ = 'Miroslav Shubernetskiy'
 __email__ = 'miroslav@miki725.com'
-__version__ = '0.3.9'
+__version__ = '0.3.10'

url_filter/backends/django.py

@@ -1,8 +1,10 @@
 # -*- coding: utf-8 -*-
 from __future__ import absolute_import, print_function, unicode_literals
 
+from django.core.exceptions import FieldDoesNotExist
 from django.db.models.constants import LOOKUP_SEP
 
+from ..utils import suppress
 from .base import BaseFilterBackend
 
 
@@ -110,4 +112,16 @@ def filter_by_specs(self, queryset):
         for lookup, value in exclude.items():
             queryset = queryset.exclude(**{lookup: value})
 
-        return queryset.distinct()
+        to_many = self._is_any_to_many()
+        return queryset.distinct() if to_many else queryset
+
+    def _is_any_to_many(self):
+        return any(self._is_to_many(self.model, i.components) for i in self.regular_specs)
+
+    def _is_to_many(self, model, components):
+        if not components:
+            return False
+
+        with suppress(FieldDoesNotExist):
+            f = model._meta.get_field(components[0])
+            return f.one_to_many or f.many_to_many or self._is_to_many(f.related_model, components[1:])

url_filter/utils.py

@@ -1,6 +1,7 @@
 # -*- coding: utf-8 -*-
 from __future__ import absolute_import, print_function, unicode_literals
 import inspect
+from contextlib import contextmanager
 
 
 class FilterSpec(object):
@@ -242,3 +243,21 @@ def dict_pop(key, d):
     """
     d.pop(key, None)
     return d
+
+
+@contextmanager
+def suppress(e):
+    """
+    Suppress given exception type
+
+    For example::
+
+        >>> with suppress(ValueError):
+        ...     print('test')
+        ...     raise ValueError
+        test
+    """
+    try:
+        yield
+    except e:
+        pass