On Sun, Mar 21, 2010 at 8:17 AM, Henrik Genssen <[email protected]> wrote: > No one any comment on this? > is this the expected behavior? ... >>Now is there a way to force select_related tables any way in a count?
select_related() is an optimization for data retrieval. It allows you to expand a select row to include related objects in a single query. It only follows the "1" side of "1-N" relations. That is, if a book has a foreign key on author, Book has a single Author. If you request N books, you will need to issue N+1 SQL queries. With select_related, this becomes 1 SQL query, and each row in the result set includes the details of the book and the details of the single related author. This *does not* affect the row count. The number of books doesn't change as a result of including related authors in the result set. Hence, select_related() clauses are removed prior to a call to count(). select_related() is *not* a way to force a table join. If you need a table join, you need to add a filter() that traverses the join. Alternatively, you could expand your extra() clause to force the extra join condition. Yours, Russ Magee %-) -- 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.
