Changeset 4394

Timestamp:

01/22/07 20:11:08 (1 year ago)

Author:

adrian

Message:

Fixed #3283 -- Added support for empty QuerySets? via none() method. Thanks for the patch, medhat

Files:

• django/trunk/django/db/models/manager.py (modified) (3 diffs)
• django/trunk/django/db/models/query.py (modified) (9 diffs)
• django/trunk/docs/db-api.txt (modified) (1 diff)
• django/trunk/tests/modeltests/lookup/models.py (modified) (1 diff)

django/trunk/django/db/models/manager.py

@@ -1 @@
-
+, EmptyQuerySet
-from django.dispatch import dispatcher
-from django.db.models import signals
@@ -42 +42 @@
-    # PROXIES TO QUERYSET #
-    #######################
+    
+    def get_empty_query_set(self):
+        return EmptyQuerySet(self.model)
-
-    def get_query_set(self):
@@ -48 +51 @@
-        """
-        return QuerySet(self.model)
+    
+    def none(self):
+        return self.get_empty_query_set()
-
-    def all(self):

django/trunk/django/db/models/query.py

@@ -25 +25 @@
-# Larger values are slightly faster at the expense of more storage space.
-GET_ITERATOR_CHUNK_SIZE = 100
+
+class EmptyResultSet(Exception):
+    pass
-
-####################
@@ -169 +172 @@
-
-        cursor = connection.cursor()
-
+
+
+
+
+
+
-        cursor.execute("SELECT " + (self._distinct and "DISTINCT " or "") + ",".join(select) + sql, params)
-        fill_cache = self._select_related
@@ -193 +201 @@
-        counter._limit = None
-        counter._select_related = False
-
+
+
+
+
+
+
-        cursor = connection.cursor()
-        if self._distinct:
@@ -524 +537 @@
-
-        cursor = connection.cursor()
-
+
+
+
+
+
+
-        select = ['%s.%s' % (backend.quote_name(self.model._meta.db_table), backend.quote_name(c)) for c in columns]
-        cursor.execute("SELECT " + (self._distinct and "DISTINCT " or "") + ",".join(select) + sql, params)
@@ -546 +564 @@
-            self._where.append('%s.%s IS NOT NULL' % \
-                (backend.quote_name(self.model._meta.db_table), backend.quote_name(self._field.column)))
-
+
+
+
+
+
+
-        sql = 'SELECT %s %s GROUP BY 1 ORDER BY 1 %s' % \
-            (backend.get_date_trunc_sql(self._kind, '%s.%s' % (backend.quote_name(self.model._meta.db_table),
@@ -563 +586 @@
-        c._order = self._order
-        return c
+    
+class EmptyQuerySet(QuerySet):
+    def __init__(self, model=None):
+        super(EmptyQuerySet, self).__init__(model)
+        self._result_cache = []
+        
+    def iterator(self):
+        raise StopIteration
+        
+    def count(self):
+        return 0
+        
+    def delete(self):
+        pass
+
+    def _clone(self, klass=None, **kwargs):
+        c = super(EmptyQuerySet, self)._clone(klass, **kwargs)
+        c._result_cache = []
+        return c
-
-class QOperator(object):
@@ -572 +614 @@
-        joins, where, params = SortedDict(), [], []
-        for val in self.args:
-
-
-
-
+
+
+
+
+
+
+
+
-        if where:
-            return joins, ['(%s)' % self.operator.join(where)], params
@@ -629 +675 @@
-
-    def get_sql(self, opts):
-
-
+
+
+
+
+
-        return joins, where2, params
-
@@ -646 +695 @@
-            return '%s%s IN (%s)' % (table_prefix, field_name, in_string)
-        else:
-
-
-
-
-
+
-    elif lookup_type == 'range':
-        return '%s%s BETWEEN %%s AND %%s' % (table_prefix, field_name)

django/trunk/docs/db-api.txt

@@ -526 +526 @@
-    >>> Entry.objects.filter(headline__contains='Lennon').dates('pub_date', 'day')
-    [datetime.datetime(2005, 3, 20)]
+    
+``none()``
+~~~~~~~~~~
+
+**New in Django development version**
+
+Returns an ``EmptyQuerySet`` -- a ``QuerySet`` that always evaluates to 
+an empty list. This can be used in cases where you know that you should
+return an empty result set and your caller is expecting a ``QuerySet``
+object (instead of returning an empty list, for example.)
+
+Examples::
+    
+    >>> Entry.objects.none()
+    []
-
-``select_related()``

django/trunk/tests/modeltests/lookup/models.py

@@ -192 +192 @@
-[<Article: Article with \ backslash>]
-
+# none() returns an EmptyQuerySet that behaves like any other QuerySet object
+>>> Article.objects.none()
+[]
+>>> Article.objects.none().filter(headline__startswith='Article')
+[]
+>>> Article.objects.none().count()
+0
+
+# using __in with an empty list should return an empty query set
+>>> Article.objects.filter(id__in=[])
+[]
+
+>>> Article.objects.exclude(id__in=[])
+[<Article: Article with \ backslash>, <Article: Article% with percent sign>, <Article: Article_ with underscore>, <Article: Article 5>, <Article: Article 6>, <Article: Article 4>, <Article: Article 2>, <Article: Article 3>, <Article: Article 7>, <Article: Article 1>]
+
-"""}