On 17 déc. 2013, at 20:38, Karen Tracey <kmtra...@gmail.com> wrote:
> https://groups.google.com/d/msg/django-developers/0IuJssTt8tc/TxdXQ2D0thcJ
Interesting. Now I remember reading that message last year. I have three
reactions.
First, Russell and I agree that the interest has faded. Currently, the best
option is (probably) django-nonrel. We're open to suggestions that help
django-nonrel but we aren't working towards a merge.
Second, Russell talks about the ORM API, not about the ORM code. He implies is
that little code, if any, would be shared between the relational and the
non-relational backends. We agree again.
Third, his examples conveniently ignore relations, which is where both
relational databases and Django’s ORM shine. That’s where I disagree. Here’s an
interesting example (extracted from a real project):
(Subscription.objects
.valid_for_reporting()
.filter(inception_date__gte=self.start_dt, inception_date__lt=self.end_dt)
.annotate(rentals_count=Count('subscriber__rentals'))
.annotate(rentals_duration=Sum('subscriber__rentals__dn_duration'))
.annotate(rentals_distance=Sum('subscriber__rentals__dn_distance'))
.annotate(rentals_net_amount=Sum('subscriber__rentals__pricing__net_amount'))
.annotate(rentals_vouchers_net_amount=Sum('subscriber__rentals__pricing__voucher_details__net_amount'))
.order_by('inception_date')
.values(...)
)
I have some doubts about the practicality of running such a query on an NoSQL
datastore or translating it automatically to a map-reduce job.
So, while it’s technically possible to implement parts of the ORM’s APIs on top
of a non-relational database — as proved by the django-nonrel project — there
isn’t much enthusiasm because the APIs are optimized for joins, which SQL
databases are good at while NoSQL storage engines aren’t.
--
Aymeric.
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