Sorry, here's the example.
Or is there any simpler way to achieve the same thing?
JJ.
class Book(models.Model):
title = ...
main_author = ForeignKey(Author, null=True)
co_authors = ManyToManyField(Author)
class Reprint(models.Model):
book = ForeignKey(Book)
class BooksManager(models.Manager):
def select_related_ex(self, query=None):
books = query.select_related()
main_authors = self.main_authors_in_bulk()
co_authors = self.main_authors_in_bulk()
reprints = self.reprints_in__bulk()
for book in books:
book.cached_main_author = main_authors.get(book.id, None)
book.cached_co_authors = co_authors.get(book.id, None)
book.cached_reprints = reprints.get(book.id, None)
def main_authors_in_bulk(self):
query = """
SELECT book_book.id, book_main_author.first_name,
book_main_author.last_name
FROM book_book, book_main_author
WHERE
book_book.book_id = book_main_author.initials
"""
cursor = db.connection.cursor()
cursor.execute(query)
values = {}
for id, first_name, last_name in cursor.fetchall():
values[id] = mymodel.Author(first_name=first_name,
last_name=last_name)
return values
def co_authors_in_bulk(self):
query = """
SELECT
book_book_co_authors.book_id,
book_author.initials, book_author.first_name,
book_author.last_name
FROM book_book_co_authors, book_author
WHERE
book_book_co_authors.author_id = book_author.initials
ORDER BY
book_author.initials ASC
"""
cursor = db.connection.cursor()
cursor.execute(query)
values = {}
for id, first_name, last_name in cursor.fetchall():
ids = values.get(id, [])
ids.append(mymodel.Author(first_name=first_name,
last_name=last_name))
values[id] = ids
return values
def reprints_in_bulk():
...
On Jul 13, 12:26 pm, Malcolm Tredinnick <[EMAIL PROTECTED]>
wrote:
> On Fri, 2007-07-13 at 09:57 +0000, jj wrote:
> > I posted earlier about performance issues trying to display many books
> > in one single page. I've since fixed the problems by reducing the
> > number of SQL queries from 12 per book, to just 11 overall. I also
> > perform filtering based on user's permissions up-front. Big
> > performance boost.
>
> > I ended writing several managers. Typing almost the same code in each
> > manager. Encapsulating it all in a hand-crafted select_related_ex()
> > that also fetches ManyToManyField's and ForeignKey's where
> > "null=True".
>
> > It occurred to me that such code could/should probably be made generic
> > and part of the standard Django distribution.
>
> You haven't included an example of what you're talking about, so it's
> difficult to comment on the specifics.
>
> Malcolm
>
> --
> Telepath required. You know where to apply...http://www.pointy-stick.com/blog/
--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Django users" group.
To post to this group, send email to [email protected]
To unsubscribe from this group, send email to [EMAIL PROTECTED]
For more options, visit this group at
http://groups.google.com/group/django-users?hl=en
-~----------~----~----~----~------~----~------~--~---
