Does the ORM support eager fetches?
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meppum
Apr 18, 2008, 6:48:01 PM4/18/08
to Django users
I was wondering if it was possible to load a parent object and it's
child objects at the same time instead of lazily loading the children
after the parent has been retrieved?
child objects at the same time instead of lazily loading the children
after the parent has been retrieved?
Peter Rowell
Apr 18, 2008, 7:24:33 PM4/18/08
to Django users
Take a look at select_related(), it may be of some help, depending on
how you define "parent" and "child".
http://www.djangoproject.com/documentation/db-api/#select-related
"Returns a QuerySet that will automatically “follow” foreign-key
relationships, selecting that additional related-object data when it
executes its query. This is a performance booster which results in
(sometimes much) larger queries but means later use of foreign-key
relationships won’t require database queries."
how you define "parent" and "child".
http://www.djangoproject.com/documentation/db-api/#select-related
"Returns a QuerySet that will automatically “follow” foreign-key
relationships, selecting that additional related-object data when it
executes its query. This is a performance booster which results in
(sometimes much) larger queries but means later use of foreign-key
relationships won’t require database queries."
meppum
Apr 18, 2008, 8:57:30 PM4/18/08
to Django users
I read that to mean that it follows foreign key relationships "up"
from the child to the parent. Meaning that if you load
Parent.select_related() that parent.child_set() will not yet have been
loaded. Or did I read it wrong?
On Apr 18, 7:24 pm, Peter Rowell <hedron...@gmail.com> wrote:
> Take a look at select_related(), it may be of some help, depending on
> how you define "parent" and "child".http://www.djangoproject.com/documentation/db-api/#select-related
from the child to the parent. Meaning that if you load
Parent.select_related() that parent.child_set() will not yet have been
loaded. Or did I read it wrong?
On Apr 18, 7:24 pm, Peter Rowell <hedron...@gmail.com> wrote:
> Take a look at select_related(), it may be of some help, depending on
alex....@gmail.com
Apr 18, 2008, 11:32:09 PM4/18/08
to Django users
No, you are correct, it does not follow reverse foreign keys, at least
not yet, there was a discussion about this a few days ago, if this is
of importance to you, you could either held write the code for django
to support following reverse foreign keys in select_related() or you
could write the SQL manually.
not yet, there was a discussion about this a few days ago, if this is
of importance to you, you could either held write the code for django
to support following reverse foreign keys in select_related() or you
could write the SQL manually.
Malcolm Tredinnick
Apr 18, 2008, 11:59:43 PM4/18/08
to django...@googlegroups.com
On Fri, 2008-04-18 at 17:57 -0700, meppum wrote:
> I read that to mean that it follows foreign key relationships "up"
> from the child to the parent. Meaning that if you load
> Parent.select_related() that parent.child_set() will not yet have been
> loaded. Or did I read it wrong?
See a post from earlier this week about why select_related() for
anything that returns multi-valued results (which includes reverse
ForeignKeys) is not implemented yet and won't be for a while:
--
A clear conscience is usually the sign of a bad memory.
http://www.pointy-stick.com/blog/
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