[Zope] Counting the elements of a result in a ZCatalog

[Janko Hauser]

Am 05.06.2008 um 12:56 schrieb Marco Bizzarri:

> Hi all.
>
> I need to query a ZCatalog, and I would like to know how many elements
> are there. I'm working from inside a python product, so, I could do
> something like:
>
> results = Catalog(criteria)
> return len(results)
>
>
> But this creates a number of objects which are completly useless for
> me. After all, I'm interested in just the length, not in the objects.
>
> I could do something like this:
>
> results = Catalog(criteria, sort_limit=1)
> return results.actual_result_count
>
> since I should have a LazyMap, which does not (should not) actually
> load all the objects (at least, I hope so).
>
> This does not work if I have no result. So, what I should do would be:
>
> results = Catalog(criteria, sort_limit=1)
> if len(results) == 0:
>    return 0
> return results.actual_result_count
>
> Am I missing something?

Yes, you do the expensive operation just for the test, so there is no  
benefit.

if result:
    result_len = results.actual_result_count
else:
    result_len = 0

return result_len

HTH,

__Janko
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