Barun Singh wrote:
[...]
> consider the following app with two models linked through a join
> table:
>
>
> class User < ActiveRecord::Base
> has_many :boxes_users
> has_many :boxes, :through => :boxes_users
> end
>
> class Box < ActiveRecord::Base
> named_scope :brown, :conditions => {:color => 'brown'}
> end
>
> class BoxesUser < ActiveRecord::Base
> belongs_to :box
> belongs_to :user
> end
Off the main topic for a second: if the join table needs a separate
model, change its name to something more descriptive. "BoxesUser" is
not a terribly descriptive name. "Assignment" or "BoxAssignment" might
be clearer.
>
>
> If I run this query:
> >> User.find(1).boxes.brown
>
> The following SQL is generated:
>
> SELECT "boxes".* FROM "boxes" INNER JOIN "boxes_users" ON "boxes".id =
> "boxes_users".box_id WHERE (("boxes_users".user_id = 1)) AND
> (("boxes"."color" = 'brown') AND (("boxes_users".user_id = 1)))
>
>
> Note that the ("boxes_users".user_id = 1) condition is repeated in the
> sql query. Think does not impact the query results (though it does
> makes parsing the development log a bit more tedious). Just curious
> if anyone knows if this could potentially lead to less efficient
> database queries in some circumstances, or have other secondary
> effects?
I doubt it. I would guess that the DB's query optimizer would notice
the duplicate condition right away and remove it.
Best,
--
Marnen Laibow-Koser
http://www.marnen.org
[email protected]
--
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