Rails - Jul 2009 - repeated conditions in sql queries

This is a minor question, mostly for curiosity:  using rails 2.3, does
anybody else notice repeated conditions in sql queries?

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


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?

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
marnen-sbuyVjPbboAdnm+yROfE0A@public.gmane.org

-- 
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