On 19 Paź, 20:21, Daniel Roseman <dan...@roseman.org.uk> wrote:
>
> You can't do this in one query with Django's ORM.
>
> One way of doing it in two queries might be to get use .annotate() to
> add the max id of the related objectrevision for each revision, then
> get all those objectrevisions (untested):
>
> objects = Object.objects.all().annotate(revision_id=Max
> ('objectrevision__id'))
> objectrevisions = ObjectRevision.objects.filter(id__in=
> [o.revision_id for o in objects])
>
I found this solution, but we are talking about thousends of objects,
so SQL query would be really huge. I' tested it with MySQL Query
Browser
and passing ton of ids to `WHERE id IN (...)` clause was causing major
overhead
comparing to using JOIN.
Fortunately, in the mean time, I've found a nice solution using SQL
views:
http://wolfram.kriesing.de/blog/index.php/2007/django-nice-and-critical-article#comment-48425
This is not strictly a solution to the problem I asked, but it allows
to hide SQL under the floor
and just use Django ORM in everydays work.
Anyway, thank you for confirmation on this limitation, I wasn't sure
about it.
--
Tomasz Zielinski
http://pyconsultant.eu
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