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belongd_to proxy loads from database every time if record is missing
Reported by Robin Salkeld | July 27th, 2009 @ 10:18 PM | in 3.x
Greetings all,
I'm hitting some interesting behaviour in the association proxy code that seems to be intentional, but seems non-optimal and is actually causing quite a bit of unnecessary DB querying in our case.
Basically it looks like there is some special-casing of the BelongsToAssociation proxy to avoid setting its target to nil. In particular there are these lines in association.rb:
define_method(reflection.name) do |*params|
force_reload = params.first unless params.empty?
association = association_instance_get(reflection.name)
if association.nil? || force_reload
association = association_proxy_class.new(self, reflection)
retval = association.reload
if retval.nil? and association_proxy_class == BelongsToAssociation
association_instance_set(reflection.name, nil)
return nil
end
association_instance_set(reflection.name, association)
end
association.target.nil? ? nil : association
end
I can understand not returning the proxy when the target is nil, since the proxy can't impersonate nil. However, not setting the proxy into the instance variable means the DB will be requeried every time for no good reason, and it seems to me that assigning the proxy will still have the correct behaviour from the model's perspective. The same thing happens on preloading, meaning that preloading doesn't actually do anything for missing records.
Does anyone know the reason for this behaviour? I'm using Rails 2.3.2. Here's a reproduction of the problem from the application's perspective.
class Alpha < ActiveRecord::Base
end
class Beta < ActiveRecord::Base
belongs_to :alpha
end
a = Alpha.create
b = Beta.create :alpha => a
a.destroy
b_loaded = Beta.find(b.id, :include => :alpha)
b_loaded.loaded_alpha? # => false (or nil, rather, but not true)
b_loaded.alpha # => nil
b_loaded.loaded_alpha? # => still nil rather than true
b_loaded.alpha # => nil (and hits the DB again)
Thanks!
Comments and changes to this ticket
-
Robin Salkeld July 27th, 2009 @ 10:19 PM
Whoops, didn't format the example correctly. Sorry - I'm a lighthouse noob. :)
class Alpha < ActiveRecord::Base end
class Beta < ActiveRecord::Base
belongs_to :alphaend
a = Alpha.create b = Beta.create :alpha => a a.destroy
b_loaded = Beta.find(b.id, :include => :alpha) b_loaded.loaded_alpha? # => false (or nil, rather, but not true) b_loaded.alpha # => nil b_loaded.loaded_alpha? # => still nil rather than true b_loaded.alpha # => nil (and hits the DB again)
-
Robin Salkeld July 27th, 2009 @ 10:19 PM
Whoops, didn't format the example correctly. Sorry - I'm a lighthouse noob. :)
class Alpha < ActiveRecord::Base end
class Beta < ActiveRecord::Base
belongs_to :alphaend
a = Alpha.create b = Beta.create :alpha => a a.destroy
b_loaded = Beta.find(b.id, :include => :alpha) b_loaded.loaded_alpha? # => false (or nil, rather, but not true) b_loaded.alpha # => nil b_loaded.loaded_alpha? # => still nil rather than true b_loaded.alpha # => nil (and hits the DB again)
-
-
Dan Pickett May 9th, 2010 @ 06:55 PM
- Assigned user set to “Ryan Bigg”
Robin,
Could you provide a failing test case that verifies this errant behavior?
Ryan - assigning to you in order to mark this as stale or incomplete.
-
Ryan Bigg May 9th, 2010 @ 10:16 PM
- State changed from “new” to “incomplete”
-
Santiago Pastorino February 2nd, 2011 @ 04:39 PM
- State changed from “incomplete” to “open”
- Importance changed from “” to “”
This issue has been automatically marked as stale because it has not been commented on for at least three months.
The resources of the Rails core team are limited, and so we are asking for your help. If you can still reproduce this error on the 3-0-stable branch or on master, please reply with all of the information you have about it and add "[state:open]" to your comment. This will reopen the ticket for review. Likewise, if you feel that this is a very important feature for Rails to include, please reply with your explanation so we can consider it.
Thank you for all your contributions, and we hope you will understand this step to focus our efforts where they are most helpful.
-
Santiago Pastorino February 2nd, 2011 @ 04:39 PM
- State changed from “open” to “stale”
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Jeremy Kemper
Robin Salkeld
Ryan Bigg