Re: Django aggregation does excessive GROUP BY clauses

Opened a bug:

https://code.djangoproject.com/ticket/17144

I think I might take a crack at fixing this one.

On Nov 1, 9:06 pm, Karen Tracey <kmtra...@gmail.com> wrote:
> On Tue, Nov 1, 2011 at 6:19 PM, christian.oudard <christian.oud...@gmail.com
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> > wrote:
> > I am doing a very simple aggregation using the Django ORM, and it is
> > producing a GROUP BY clause that includes the data field, which is
> > very large, and is slowing down the query by over 100-fold.
>
> > Here is a simplified version of the model:
>
> > class Document(models.Model):
> >    data = models.TextField()
>
> > class Attachment(models.Model):
> >    document = models.ForeignKey(Document)
>
> > And the query I am running:
>
> > Document.objects.annotate(num_attachments=Count('attachment'))
>
> The SQL generated by the ORM for this query changed between Django version
> 1.2 and 1.3. The 1.2 SQL did a group by only on the id field. With 1.3
> we're getting id twice and then all other fields in the model. Bisection
> shows the change was made with r14715:
>
> https://code.djangoproject.com/changeset/14715
>
> It certainly looks to me like the old SQL was correct and preferable for
> this particular case. In a brief search I did not find a ticket reporting
> this issue -- could you open one?
>
> Karen
> --http://tracey.org/kmt/

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