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#3455 ✓stale
Artūras Šlajus

AR belongs_to :include option doesn't do anything

Reported by Artūras Šlajus | November 3rd, 2009 @ 10:50 AM

It seems that eager loading of AR for belongs_to associations is broken.

With the new strategy for has_many associations, belongs_to doesn't left join relevant tables (which is only logical thing to do for 1:1 relationships).


class SolarSystem < ActiveRecord::Base
  has_many :fow_ss_entries, :dependent => :delete_all

class FowSsEntry < ActiveRecord::Base
  belongs_to :galaxy
  belongs_to :solar_system
  belongs_to :player

  named_scope :for, { |galaxy, player|
    galaxy = if galaxy.is_a? Galaxy
    player = if player.is_a? Player

      :conditions => {:galaxy_id => galaxy, :player_id => player},
      :include => :solar_system
FowSsEntry.for(1,1).each { |fse| fse.solar_system }

Generates this:

[2009-11-03 00:35:26|main|debug] FowSsEntry Load (0.0ms)  SELECT * FROM 
`fow_ss_entries` WHERE (`fow_ss_entries`.`galaxy_id` = 1 AND 
`fow_ss_entries`.`player_id` = 1)
[2009-11-03 00:35:26|main|debug] SolarSystem Load (0.0ms)  SELECT * FROM 
`solar_systems` WHERE (`solar_systems`.`id` = 57)
[2009-11-03 00:35:26|main|debug] SolarSystem Load (0.0ms)  SELECT * FROM 
`solar_systems` WHERE (`solar_systems`.`id` = 157)
[2009-11-03 00:35:26|main|debug] SolarSystem Load (0.0ms)  SELECT * FROM 
`solar_systems` WHERE (`solar_systems`.`id` = 313)
[2009-11-03 00:35:26|main|debug] SolarSystem Load (0.0ms)  SELECT * FROM 
`solar_systems` WHERE (`solar_systems`.`id` = 314)

It should be left outer join. If you force it into join mode, by providing :order => "" to the scope, it works as expected, but it shouldn't be that way.

Comments and changes to this ticket

  • David Trasbo

    David Trasbo April 14th, 2010 @ 08:42 PM

    I was able to duplicate this with version 2.3.5 of Rails:

    ➜  code  rails -v                        
    Rails 2.3.5
    ➜  code  rails named_scope_include_option
    ➜  code  cd named_scope_include_option 
    ➜  named_scope_include_option  script/generate model foo bar_id:integer
    ➜  named_scope_include_option  script/generate model bar
    ➜  named_scope_include_option  rake db:migrate
    (in /Users/dtrasbo/code/named_scope_include_option)
    ➜  named_scope_include_option  script/console
    Loading development environment (Rails 2.3.5)
    ruby-1.8.7-p249 > Foo.baz.each do |foo|
    ruby-1.8.7-p249 >
    ruby-1.8.7-p249 ?>  end
     => [#<Foo id: 1, bar_id: 1, created_at: "2010-04-14 19:31:29", updated_at: "2010-04-14 19:31:29">]

    Sure enough, the log shows two entries:

    SELECT * FROM "foos"
    SELECT * FROM "bars" WHERE ("bars"."id" = 1)
  • David Trasbo

    David Trasbo April 14th, 2010 @ 08:43 PM

    Here's the Foo model, by the way. Bar has no code in it.

    class Foo < ActiveRecord::Base
      belongs_to :bar
      named_scope :baz, :include => :bar
  • Santiago Pastorino

    Santiago Pastorino February 2nd, 2011 @ 04:35 PM

    • State changed from “new” to “open”
    • Tag changed from 2.3.4, activerecord to 234, activerecord

    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

    Santiago Pastorino February 2nd, 2011 @ 04:35 PM

    • State changed from “open” to “stale”
  • bingbing
  • Julian Mehnle

    Julian Mehnle March 29th, 2011 @ 06:37 AM

    • Tag changed from 234, activerecord to 2.3.11, 2311, 234, activerecord

    This is still broken in 2.3.11. Didn't have a chance to test it with ActiveRecord/Rails 3 yet.

  • Dave Schweisguth

    Dave Schweisguth April 10th, 2011 @ 01:27 AM

    In Rails 3.0.6

    • when querying multiple objects, eager-loaded belongs_to are loaded in a single separate query with 'where id in (...)', which makes sense since left joining could bring in the same date more than once. I'd have sworn this was the Rails 2.3.11 behavior but I no longer have a Rails 2.3.11 app handy to check.

    • there is still a bug in that when querying a single object with find, ActiveRecord should know that it can left join, but it still takes a second query to get the belonged-to object.

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