#2247 has_one :through produces invalid SQL - Ruby on Rails

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#2247 ✓resolved

has_one :through produces invalid SQL

Reported by Pascal Ehlert | March 16th, 2009 @ 06:42 AM | in 3.x

I've experienced a weird issue today which I'd like someone to confirm before I start working on a patch.

When using has_one :through with another has_one association like so:


  class Donor
    has_one  :primary_grouping, :class_name => "DonorGrouping", :conditions => { :primary => true }
    has_one  :primary_group, :through => :primary_grouping, :source => :donor_group
  
    has_many :donor_groupings, :conditions => { :primary => false }
    has_many :groups, :through => :donor_groupings, :source => :donor_group
  end

  class DonorGrouping < ActiveRecord::Base
    belongs_to :donor_group
    belongs_to :donor
  end

While the has_many association works flawlessly, a Donor.first.primary_group gives:


>> Donor.first.primary_group
ActiveRecord::StatementInvalid: PGError: ERROR:  column donor_groups.donor_id does not exist
LINE 1: ...CT "donor_groups".* FROM "donor_groups"    WHERE (donor_grou...
                                                             ^
: SELECT "donor_groups".* FROM "donor_groups"    WHERE (donor_groups.donor_id = 18 )

Where the requested donor_id of 18 is the id of Donor.first..

This could also be related to #1167 which has never been resolved complete as it seems.

Pretty severe issue, isn't it?!

Comments and changes to this ticket

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njakobsen March 31st, 2009 @ 01:37 AM
I have the same problem in rails 2.3.2
```
class Item
has_one :default_digital_object, :through => :item_digital_objects, :source => :digital_object
end
```
Item.first.default_digital_object produces the following SQL:

@@@SELECT "digital_objects".* FROM "digital_objects" WHERE (digital_objects.item_id = 14891 )@@@

It seems to be ignoring the :through parameter.
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Joshua White June 4th, 2009 @ 12:01 AM
I'm having the same issue on 2.3.2 ... I can't get has_one through on a belongs_to relationsbip

ExamRecord.rb (contains patient_id )

belongs_to :patient
has_one :history, :through => :patient
has_many :insurance_providers, :through => :patient

Patient.rb
has_many :exam_records
has_many :insurance_providers
has_one :history

History.rb (contains patient_id)
belongs_to :patient

InsuranceProvider.rb
belongs_to :patient

So on the console if I do

ExamRecord.first.insurance_providers, I get my array of insurance providers fine...

ExamRecord.first.history I get

ActiveRecord::HasManyThroughSourceAssociationMacroError: Invalid source reflection macro :has_one for has_many :history, :through => :patient. Use :source to specify the source reflection.
```
    from /usr/local/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/active_record/reflection.rb:301:in `check_validity!'
    from /usr/local/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/active_record/associations/has_many_through_association.rb:5:in `initialize'
    from /usr/local/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/active_record/associations.rb:1230:in `new'
    from /usr/local/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/active_record/associations.rb:1230:in `history'
    from (irb):29
```
I have tried specifying :source => :history and I get

ExamRecord.first.history ActiveRecord::HasManyThroughSourceAssociationMacroError: Invalid source reflection macro :has_one for has_many :history, :through => :patient. Use :source to specify the source reflection.
```
    from /usr/local/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/active_record/reflection.rb:301:in `check_validity!'
    from /usr/local/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/active_record/associations/has_many_through_association.rb:5:in `initialize'
    from /usr/local/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/active_record/associations.rb:1230:in `new'
    from /usr/local/lib/ruby/gems/1.8/gems/activerecord-2.3.2/lib/active_record/associations.rb:1230:in `history'
    from (irb):31
```
Any Ideas?
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Joshua White June 4th, 2009 @ 12:04 AM
Apparently this is discussed in #1149, the has_one through only works when the join is a has_many or belongs_to.
Jeremy Kemper May 4th, 2010 @ 06:48 PM
- Milestone changed from “2.x” to “3.x”
[bulk edit]
Jon Leighton December 12th, 2010 @ 01:56 PM
- Assigned user set to “Aaron Patterson”
- Importance changed from “” to “”
This is no longer an issue can can be closed. The behaviour is verified by the test test_has_one_through_with_has_one which exists in test/cases/associations/has_one_through_associations_test.rb and already passes. Thanks.
Aaron Patterson December 15th, 2010 @ 07:19 PM
- State changed from “new” to “resolved”
Closing per Jon's comment.
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