On Wed, Feb 10, 2010 at 3:11 PM, Jerome Leclanche <adys...@gmail.com> wrote: > Hi list > > Using David Cramer's really nice replacement devserver > (http://github.com/dcramer/django-devserver), I noticed a bunch of > huge queries in some table generation code. Example: > http://dpaste.com/156907/ > This is from one of my smallest tables, bigger ones with 120+ish rows > can take multiple ms to query. > > I narrowed it down to a SomeModel.some_reverse_foreignkey.exists(). > Using something as simple as .only("id").exists() will make the query > several dozen times faster. > > Is this a bug, or am I missing something in exists() behaviour? From > what I understood, it's supposed to be faster than count() in > situations where I just need to know whether there are rows present.
It certainly doesn't look right; .exists() should be faster than .count(), and having all the extra columns in the query looks a little weird. However, to say for sure, we need a few more details: * Does this only happen when using David's devserver, or does it happen in a normal Django shell? * Can you give a *specific* example of a model and query that is causing this? Or, if it's happening in the process of running a management command or other Django-internal activity, what do you need to do to stimulate the problem? * Are you doing anything interesting with select_related() or anything like that? * What version of Django (including SVN revision, if appropriate) are you using? Yours, Russ Magee %-) -- You received this message because you are subscribed to the Google Groups "Django developers" group. To post to this group, send email to django-develop...@googlegroups.com. To unsubscribe from this group, send email to django-developers+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/django-developers?hl=en.
