list_editable duplicate queries

Hi there,

I think that I have found a bug with the rendering of list_editable
objects in the change list. The problem that I am running into is that
if I include a field that is a foreign key in list_editable, the
change_list hits the database every time that it renders the foreign
key's widget. This means that it hits the database O(m*n) times where
m is the number of editable foreign keys in the admin model and n is
the number of rows being rendered in the change_list.

For example, say that we have the following models:

class Host(models.Model):
name = models.CharField(max_length=128, unique=True)

class Account(models.Model):
host = models.ForeignKey(Host, related_name="accounts")
name = models.CharField(max_length=128)

...and the following admin model:

class AccountAdmin(admin.ModelAdmin):
list_display = ('name', 'host')
list_editable = ('host',)

Then if we load up a bunch of data (one host, 40 accounts) and go to
the change_list (/admin/accounts/account), we will find that the
database is hit (m*n)+3 = 43 times. The queries that it executes are
as follows:

EXECUTIONS | TIME | QUERY

40 | 384 ms | SELECT "hosts_host"."id", "hosts_host"."name" FROM
"hosts_host"

1 | 17 ms | SELECT "auth_message"."id", "auth_message"."user_id",
"auth_message"."message" FROM "auth_message" WHERE
"auth_message"."user_id" = %s

1 | 0 ms | SELECT COUNT(*) FROM "accounts_account"

1 | 0 ms | SELECT "accounts_account"."id",
"accounts_account"."host_id", "accounts_account"."name",
"hosts_host"."id", "hosts_host"."name" FROM "accounts_account" INNER
JOIN "hosts_host" ON ("accounts_account"."host_id" =
"hosts_host"."id") ORDER BY "accounts_account"."id" DESC

As you can see, the vast majority of the hits (40/43) were for the
exact same query and served only to get a list of all of the hosts. I
think that this occurs when the foreignkey Select widget's options are
rendered at django/forms/widgets.py:~411.

I realize that I am probably doing something wrong, so any advice
about the correct way of doing this would be appreciated. If this is a
legitimate bug, is there anything that I can do to avoid it but still
get the same functionality?

Thanks!

PS: Please let me know if you need any more information (screen shots,
etc).

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