Changeset 7220

Timestamp:

03/11/08 00:21:50 (7 months ago)

Author:

mtredinnick

Message:

queyrset-refactor: Added error reporting if somebody tries to order by a multi-valued field.

Files:

• django/branches/queryset-refactor/django/db/models/sql/query.py (modified) (1 diff)
• django/branches/queryset-refactor/docs/db-api.txt (modified) (1 diff)
• django/branches/queryset-refactor/tests/regressiontests/queries/models.py (modified) (1 diff)

django/branches/queryset-refactor/django/db/models/sql/query.py

@@ -510 +510 @@
-        if not alias:
-            alias = self.get_initial_alias()
-
-
+
+
+
+
-        alias = joins[-1][-1]
-        col = target.column

django/branches/queryset-refactor/docs/db-api.txt

@@ -541 +541 @@
-
-...since the ``Blog`` model has no default ordering specified.
+
+You can only order by model fields that have a single value attached to them
+for each instance of the model. For example, non-relations, ``ForeignKey`` and
+``OneToOneField`` fields. Explicitly, you can't order by a ``ManyToManyField``
+or a reverse ``ForeignKey`` relation. There's no naturally correct ordering
+for many-valued fields and a lot of the alternatives are not psosible to
+express in SQL very efficiently.
-
-**New in Django development version:** If you don't want any ordering to be

django/branches/queryset-refactor/tests/regressiontests/queries/models.py

@@ -419 +419 @@
-[<Ranking: 1: a3>, <Ranking: 2: a2>, <Ranking: 3: a1>]
-
+# Ordering by a many-valued attribute (e.g. a many-to-many or reverse
+# ForeignKey) doesn't make sense (there's no natural ordering).
+>>> Item.objects.all().order_by('tags')
+Traceback (most recent call last):
+...
+FieldError: Cannot order by many-valued field: 'tags'
+
-# If we replace the default ordering, Django adjusts the required tables
-# automatically. Item normally requires a join with Note to do the default