Merge pull request #577 from orf/patch-4

Add 'tree_id', 'lft' to index_together. Thanks @orf :)

.travis.yml

@@ -1,5 +1,8 @@
 sudo: false
 language: python
+cache: pip
+git:
+  depth: 1
 
 python:
   - "3.6"

mptt/models.py

@@ -326,8 +326,10 @@ def register(meta, cls, **kwargs):
 
                 bases.insert(0, MPTTModel)
                 cls.__bases__ = tuple(bases)
-
-            if _get_tree_model(cls) is cls:
+
+            is_cls_tree_model = _get_tree_model(cls) is cls
+
+            if is_cls_tree_model:
                 # HACK: _meta.get_field() doesn't work before AppCache.ready in Django>=1.8
                 # ( see https://code.djangoproject.com/ticket/24231 )
                 # So the only way to get existing fields is using local_fields on all superclasses.
@@ -336,12 +338,20 @@ def register(meta, cls, **kwargs):
                     if hasattr(base, '_meta'):
                         existing_field_names.update([f.name for f in base._meta.local_fields])
 
-                for key in ('left_attr', 'right_attr', 'tree_id_attr', 'level_attr'):
-                    field_name = getattr(cls._mptt_meta, key)
+                mptt_meta = cls._mptt_meta
+                field_names = (mptt_meta.left_attr, mptt_meta.right_attr, mptt_meta.tree_id_attr, mptt_meta.level_attr)
+
+                for field_name in field_names:
                     if field_name not in existing_field_names:
                         field = models.PositiveIntegerField(db_index=True, editable=False)
                         field.contribute_to_class(cls, field_name)
 
+                # Add an index_together on tree_id_attr and left_attr, as these are very
+                # commonly queried (pretty much all reads).
+                index_together = (cls._mptt_meta.tree_id_attr, cls._mptt_meta.left_attr)
+                if index_together not in cls._meta.index_together:
+                    cls._meta.index_together += (index_together,)
+
             # Add a tree manager, if there isn't one already
             if not abstract:
                 # make sure we have a tree manager somewhere

tests/manage.py

@@ -0,0 +1,10 @@
+#!/usr/bin/env python
+import os
+import sys
+
+if __name__ == "__main__":
+    os.environ.setdefault("DJANGO_SETTINGS_MODULE", "settings")
+
+    from django.core.management import execute_from_command_line
+
+    execute_from_command_line(sys.argv)

tests/myapp/tests.py

@@ -2343,3 +2343,53 @@ def test_nullable_ordered_insertion_desc(self):
             2 1 1 1 2 3
             3 1 1 1 4 5
         """)
+
+
+class ModelMeta(TreeTestCase):
+    def test_index_together(self):
+        already_idx = [['tree_id', 'lft'], ('tree_id', 'lft')]
+        no_idx = [tuple(), list()]
+        some_idx = [['tree_id'], ('tree_id',), [['tree_id']], (('tree_id',),)]
+
+        for idx, case in enumerate(already_idx + no_idx + some_idx):
+            class Meta:
+                index_together = case
+                app_label = 'myapp'
+
+            # Use type() here and in test_index_together_different_attr over
+            # an explicit class X(MPTTModel):, as this throws a warning that
+            # re-registering models with the same name (which is what an explicit
+            # class does) could cause errors. Kind of... weird, but surprisingly
+            # effective.
+
+            # Use str(__name__) as __module__ must be a 'str' type and not unicode
+            # on Python 2.7
+
+            SomeModel = type(str('model_{0}'.format(idx)), (MPTTModel,), {
+                'Meta': Meta,
+                '__module__': str(__name__)
+            })
+
+            self.assertIn(('tree_id', 'lft'), SomeModel._meta.index_together)
+
+    def test_index_together_different_attr(self):
+        already_idx = [['abc', 'def'], ('abc', 'def')]
+        no_idx = [tuple(), list()]
+        some_idx = [['abc'], ('abc',), [['abc']], (('abc',),)]
+
+        for idx, case in enumerate(already_idx + no_idx + some_idx):
+            class MPTTMeta:
+                tree_id_attr = 'abc'
+                left_attr = 'def'
+
+            class Meta:
+                index_together = case
+                app_label = 'myapp'
+
+            SomeModel = type(str('model__different_attr_{0}'.format(idx)), (MPTTModel,), {
+                'MPTTMeta': MPTTMeta,
+                'Meta': Meta,
+                '__module__': str(__name__)
+            })
+
+            self.assertIn(('abc', 'def'), SomeModel._meta.index_together)