Let's say that i have a User object in @user, already loaded. I want to constantly refer to @user.role on a particular page (where User belongs_to :role), so i want to 'eager load' the role association.
For the sake of argument, let's say i wasn't able to do this in the normal way (ie with the :include option to a find call) when i loaded the user out of the database in the first place, but need to do it subsequent to that. Is that possible?
Max Williams wrote:
Let's say that i have a User object in @user, already loaded. I want to constantly refer to @user.role on a particular page (where User belongs_to :role), so i want to 'eager load' the role association.
For the sake of argument, let's say i wasn't able to do this in the normal way (ie with the :include option to a find call) when i loaded the user out of the database in the first place, but need to do it subsequent to that. Is that possible?
Just to answer my own question, sort of, i think that i can do
@user[:role] = @user.role
and that sets the instance variable which is used for subsequent calls to @user.role, effectively eager loading that association. is that correct? Is this the same thing as the eager loading would do? eg, is it precisely as prone to weird side effects as the regular eager loading?
Max Williams wrote: > Let's say that i have a User object in @user, already loaded. I want > to constantly refer to @user.role on a particular page (where User > belongs_to :role), so i want to 'eager load' the role association.
> For the sake of argument, let's say i wasn't able to do this in the > normal way (ie with the :include option to a find call) when i loaded > the user out of the database in the first place, but need to do it > subsequent to that. Is that possible?
Just to answer my own question, sort of, i think that i can do
@user[:role] = @user.role
and that sets the instance variable which is used for subsequent calls to @user.role, effectively eager loading that association. is that correct? Is this the same thing as the eager loading would do? eg, is it precisely as prone to weird side effects as the regular eager loading?
It's not at all what normal eager loading would do.
if you do
class User < ActiveRecord::Base class << self public :preload_associations end end
then you can do
User.preload_associations [user1, user2, user3], :role
(at least in rails 2.x - might very easily not work in 3.x)
Fred
Fred
One addition - it's pointless doing this unless you have more than 1 user object - it won't be any faster
Fred
Frederick Cheung wrote:
One addition - it's pointless doing this unless you have more than 1 user object - it won't be any faster
Fred
Thanks fred - that works. Faster than what, though? Than my approach?
Frederick Cheung wrote: > One addition - it's pointless doing this unless you have more than 1 > user object - it won't be any faster
> Fred
Thanks fred - that works. Faster than what, though? Than my approach?
compared to not eagerloading it at all.
Fred
Frederick Cheung wrote:
Memoize the role if necessary (although I thought AR would do that for you after the first load - not got time to check it out to be sure at the moment)
> Fred
In this case, i have a page which loads a partial twenty times. Each partial calls a method on the user object (current_user as it happens) which inspects its associated role object. So, if i don't eager load, then the role gets loaded twenty times. I might be misunderstanding your point though.
If it's the same user object throughout active record will cache the loaded role object for you - no need for eager loading here.
Fred
Frederick Cheung wrote: