#4399: Add __nonzero__ to allow querysets to efficiently test for emptiness
------------------------------------------+---------------------------------
Reporter: Michael Axiak <[EMAIL PROTECTED]> | Owner: adrian
Status: new | Component: Database wrapper
Version: SVN | Keywords:
database,performance,existence,patch
Stage: Unreviewed | Has_patch: 1
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Currently, if you do:
{{{
#!python
if Model.objects.filter(Complicated):
...
}}}
you're asking for performance trouble, since it will issue a {{{__len__}}}
statement on it. Most people will solve this problem by doing:
{{{
#!python
if Model.objects.filter(Complicated).count() > 0:
...
}}}
But this is '''still''' much slower than doing a SELECT LIMIT 1. Thus, I
propose adding a {{{__nonzero__}}} function, so that the first method of
checking for emptiness does the right thing.
(http://docs.python.org/ref/customization.html)
--
Ticket URL: <http://code.djangoproject.com/ticket/4399>
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