#16647: Default filters: pacth to add QuerySet support for random plus a new
shuffle filter
-------------------------------------+-------------------------------------
Reporter: h3 | Owner: nobody
Type: New | Status: new
feature | Component: Template system
Milestone: | Severity: Normal
Version: 1.3 | Keywords:
Resolution: | Has patch: 1
Triage Stage: Design | Needs tests: 1
decision needed | Easy pickings: 0
Needs documentation: 1 |
Patch needs improvement: 1 |
UI/UX: 0 |
-------------------------------------+-------------------------------------
Changes (by akaariai):
* needs_docs: 0 => 1
* stage: Unreviewed => Design decision needed
* needs_tests: 0 => 1
* needs_better_patch: 0 => 1
Comment:
I am not sure this is a good idea. The problem is that qs.order_by('?')[0]
might be really expensive. If I am not mistaken, the DB must go through
the whole result set and sort everything. Even if the DB returns just one
row, that can be expensive. I am afraid that users of random do not
realize this, as how could a fetch of just a single object cost much...
Also, in the patch you use len(qs). That means the queryset gets evaluated
(or at least count(*) is evaluated) there. try - except indexerror is
better.
Setting this to design decision needed.
--
Ticket URL: <https://code.djangoproject.com/ticket/16647#comment:2>
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