Fixed #9997 -- Fixed use of ValuesQuerySets as rvalues in filters.

Previous behaviour was pretty stupid. Let's never speak of it again. New
behaviour both works and is documented.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@9759 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/models/query.py

@@ -798,6 +798,20 @@ class ValuesQuerySet(QuerySet):
 
         super(ValuesQuerySet, self)._setup_aggregate_query()
 
+    def as_sql(self):
+        """
+        For ValueQuerySet (and subclasses like ValuesListQuerySet), they can
+        only be used as nested queries if they're already set up to select only
+        a single field (in which case, that is the field column that is
+        returned). This differs from QuerySet.as_sql(), where the column to
+        select is set up by Django.
+        """
+        if ((self._fields and len(self._fields) > 1) or
+                (not self._fields and len(self.model._meta.fields) > 1)):
+            raise TypeError('Cannot use a multi-field %s as a filter value.'
+                    % self.__class__.__name__)
+        return self._clone().query.as_nested_sql()
+
 class ValuesListQuerySet(ValuesQuerySet):
     def iterator(self):
         self.query.trim_extra_select(self.extra_names)

docs/ref/models/querysets.txt

@@ -1136,6 +1136,7 @@ The above code fragment could also be written as follows::
     inner_q = Blog.objects.filter(name__contains='Cheddar').values('pk').query
     entries = Entry.objects.filter(blog__in=inner_q)
 
+
 .. versionchanged:: 1.1
     In Django 1.0, only the latter piece of code is valid.
 
@@ -1144,6 +1145,21 @@ accesses the internal ``query`` attribute and requires a ``ValuesQuerySet``.
 If your code doesn't require compatibility with Django 1.0, use the first
 form, passing in a queryset directly.
 
+If you pass in a ``ValuesQuerySet`` or ``ValuesListQuerySet`` (the result of
+calling ``values()`` or ``values_list()`` on a queryset) as the value to an
+``__in`` lookup, you need to ensure you are only extracting one field in the
+result. For example, this will work (filtering on the blog names)::
+
+    inner_qs = Blog.objects.filter(name__contains='Ch').values('name')
+    entries = Entry.objects.filter(blog__name__in=inner_qs)
+
+This example will raise an exception, since the inner query is trying to
+extract two field values, where only one is expected::
+
+    # Bad code! Will raise a TypeError.
+    inner_qs = Blog.objects.filter(name__contains='Ch').values('name', 'id')
+    entries = Entry.objects.filter(blog__name__in=inner_qs)
+
 .. warning::
 
     This ``query`` attribute should be considered an opaque internal attribute.

tests/regressiontests/queries/models.py

@@ -1022,6 +1022,22 @@ nothing).
 >>> print Annotation.objects.filter(notes__in=Note.objects.filter(note="xyzzy")).query
 SELECT ...
 
+Bug #9997 -- If a ValuesList or Values queryset is passed as an inner query, we
+make sure it's only requesting a single value and use that as the thing to
+select.
+>>> Tag.objects.filter(name__in=Tag.objects.filter(parent=t1).values('name'))
+[<Tag: t2>, <Tag: t3>]
+
+# Multi-valued values() and values_list() querysets should raise errors.
+>>> Tag.objects.filter(name__in=Tag.objects.filter(parent=t1).values('name', 'id'))
+Traceback (most recent call last):
+...
+TypeError: Cannot use a multi-field ValuesQuerySet as a filter value.
+>>> Tag.objects.filter(name__in=Tag.objects.filter(parent=t1).values_list('name', 'id'))
+Traceback (most recent call last):
+...
+TypeError: Cannot use a multi-field ValuesListQuerySet as a filter value.
+
 Bug #9985 -- qs.values_list(...).values(...) combinations should work.
 >>> Note.objects.values_list("note", flat=True).values("id").order_by("id")
 [{'id': 1}, {'id': 2}, {'id': 3}]