On May 27, 7:45 pm, "Russell Keith-Magee" <[EMAIL PROTECTED]>
wrote:
> On Wed, May 28, 2008 at 2:38 AM, radioflyer <[EMAIL PROTECTED]> wrote:
>
> > Which is the most efficient, 'proper' way to get a count on a query
> > set?
>
> > t_results = Track.objects.filter(query).order_by('title')
> > count = t_results.count() # and pass 'count' to the template.
>
> > or, in the template,
>
> > <p>Your search returned {{t_results|length}} track{{t_results|
> > pluralize}}.</p>
>
> Which one is more efficient depends on other factors.
>
> .count() performs a literal SELECT COUNT(*) ... query. This will be a
> database hit every time you call it, but it is quite a fast operation.
>
> len(queryset) (which is what gets called when you use the template
> filter) will evaluate the full queryset into objects as a list, then
> check the length of that list. However, one that length has been
> evaluated, both the queryset and the length will be cached, so
> subsequent calls to iterate over the queryset or obtain the length
> will be very efficient.
>
> So - if this is a once-off check of the length, you might find that
> count() is a better option. However, if you are planning on doing
> other operations with the queryset, checking length should be faster
> in the long run.
>
> Yours,
> Russ Magee %-)
Thank Russ,
The bit on caching the the list/queryset was most helpful.
Best,
Dan J.
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