Author: lukeplant
Date: 2009-12-09 10:07:21 -0600 (Wed, 09 Dec 2009)
New Revision: 11803
Modified:
django/trunk/django/db/models/query.py
django/trunk/tests/modeltests/basic/models.py
Log:
Optimised use of 'in' operator on QuerySet using an explicit __contains__
method.
Without this change, use of 'in' on a QuerySet resulted in ._result_cache
being fully populated, which sometimes is unnecessary work.
Modified: django/trunk/django/db/models/query.py
===================================================================
--- django/trunk/django/db/models/query.py 2009-12-09 12:47:50 UTC (rev
11802)
+++ django/trunk/django/db/models/query.py 2009-12-09 16:07:21 UTC (rev
11803)
@@ -107,6 +107,36 @@
return False
return True
+ def __contains__(self, val):
+ # The 'in' operator works without this method, due to __iter__. This
+ # implementation exists only to shortcut the creation of Model
+ # instances, by bailing out early if we find a matching element.
+ pos = 0
+ if self._result_cache is not None:
+ if val in self._result_cache:
+ return True
+ elif self._iter is None:
+ # iterator is exhausted, so we have our answer
+ return False
+ # remember not to check these again:
+ pos = len(self._result_cache)
+ else:
+ # We need to start filling the result cache out. The following
+ # ensures that self._iter is not None and self._result_cache is not
+ # None
+ it = iter(self)
+
+ # Carry on, one result at a time.
+ while True:
+ if len(self._result_cache) <= pos:
+ self._fill_cache(num=1)
+ if self._iter is None:
+ # we ran out of items
+ return False
+ if self._result_cache[pos] == val:
+ return True
+ pos += 1
+
def __getitem__(self, k):
"""
Retrieves an item or slice from the set of results.
Modified: django/trunk/tests/modeltests/basic/models.py
===================================================================
--- django/trunk/tests/modeltests/basic/models.py 2009-12-09 12:47:50 UTC
(rev 11802)
+++ django/trunk/tests/modeltests/basic/models.py 2009-12-09 16:07:21 UTC
(rev 11803)
@@ -211,6 +211,14 @@
>>> Article.objects.get(id__exact=8) == Article.objects.get(id__exact=7)
False
+# You can use 'in' to test for membership...
+>>> a8 in Article.objects.all()
+True
+
+# ... but there will often be more efficient ways if that is all you need:
+>>> Article.objects.filter(id=a8.id).exists()
+True
+
# dates() returns a list of available dates of the given scope for the given
field.
>>> Article.objects.dates('pub_date', 'year')
[datetime.datetime(2005, 1, 1, 0, 0)]
--
You received this message because you are subscribed to the Google Groups
"Django updates" group.
To post to this group, send email to django-upda...@googlegroups.com.
To unsubscribe from this group, send email to
django-updates+unsubscr...@googlegroups.com.
For more options, visit this group at
http://groups.google.com/group/django-updates?hl=en.
