#2824 [Patch] has_many :through doesn't update counter_cache on join model correctly. - Ruby on Rails

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#2824 ✓resolved

[Patch] has_many :through doesn't update counter_cache on join model correctly.

Reported by Alex Tomlins | June 22nd, 2009 @ 05:09 PM | in 3.x

If you have a counter_cache on a join model used in a has_many :through association, when removing items from the association, the counter_cache doesn't get decremented correctly. e.g.

class Post < ActiveRecord::Base
  has_many :taggings
  has_many :tags, :through => :taggings
end

class Tagging < ActiveRecord::Base
  belongs_to :post, :counter_cache => true
  belongs_to :tag
end

class Tag < ActiveRecord::Base
  has_many :taggings
  has_many :posts, :through => :taggings
end

post = Post.create!()
tag1 = Tag.create!()
tag2 = Tag.create!()
post.tags << tag1
post.reload.taggings_count # => 1
post.tags = [tag2]
post.reload.taggings_count # => 2 !  Should be 1

This happens because #delete_records in HasManyThroughAssociation does a delete_all. The attached patch changes this to a destroy_all which fixes the issue.

0001-Make-has_many-through-update-counter_cache-on-join-m.patch 3.6 KB

Comments and changes to this ticket

misza222 June 23rd, 2009 @ 07:27 PM

Unfortunately this patch does not apply cleanly for me.
It comes up with an error message

Applying Make has_many :through update counter_cache on join model correctly.
error: patch failed: activerecord/test/cases/associations/has_many_through_associations_test.rb:81
error: activerecord/test/cases/associations/has_many_through_associations_test.rb: patch does not apply
Patch failed at 0001.
When you have resolved this problem run "git-am --resolved".
If you would prefer to skip this patch, instead run "git-am --skip".

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Alex Tomlins June 24th, 2009 @ 09:49 AM
Sorry, I didn't made it clear; that patch is against the 2-3-stable branch.
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misza222 June 25th, 2009 @ 02:01 PM
That works fine and updates taggings_count as expected.

This problem exists in edge rails as well. Is this change going to be somehow merged back there or patch needs to be created to deal with this issue in edge rails?

Don't be sorry Alex. It is me who didn't notice 2-3-stable in the tags for this ticket but I am very new to lighthouse and as a matter of fact to rails itself as well (and git :).
Yehuda Katz (wycats) July 3rd, 2009 @ 06:47 AM
- Assigned user set to “Yehuda Katz (wycats)”
- State changed from “new” to “open”
Would you mind making a patch against edge? I'd like to apply this :)
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Alex Tomlins July 3rd, 2009 @ 10:28 AM
No problem. Patch attached.
- 0001-Make-has_many-through-update-counter_cache__edge.patch 3.6 KB
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Peter Haza September 18th, 2009 @ 07:14 PM
Am I the only one not able to download the last patch? I'm getting an XML with some error message.
Jeremy Kemper May 4th, 2010 @ 06:48 PM
- Milestone changed from “2.x” to “3.x”
[bulk edit]
Dan Pickett May 9th, 2010 @ 07:15 PM
- Tag changed from “2-3-stable, bug, counter_cache, has_many_through, patch” to “2-3-stable, bug, bugmash, counter_cache, has_many_through, patch”
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mdrozdziel August 19th, 2010 @ 11:49 AM
- Importance changed from “” to “”
What is the status of this issue? I am using rails 2.3.8 and as far as I can see, this is still the case. Are thre any plans regarding this problem?
Neeraj Singh August 19th, 2010 @ 02:56 PM
- Tag changed from “2-3-stable, bug, bugmash, counter_cache, has_many_through, patch” to “rails 3, 2-3-stable, bug, bugmash, counter_cache, has_many_through, patch”
Just tested it on rails edge and it is an issue on edge too.
Neeraj Singh August 19th, 2010 @ 02:59 PM
@Alex Tomlins: The changes in your patch fixes the problem in rails edge.

Could you please attach two patches: one for 2-3-stable and another one for rails edge.
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Alex Tomlins August 19th, 2010 @ 03:34 PM
Sure thing.

I'll try to get onto that this evening (UK time)
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Alex Tomlins August 20th, 2010 @ 09:49 AM
Ok, patches done. They're on github here: http://github.com/unboxed/rails/tree/2-3-counter-cache-fix and here: http://github.com/unboxed/rails/tree/edge-counter-cache-fix

Let me know if you'd prefer me to create actual patch files for these.
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Alex Tomlins September 2nd, 2010 @ 09:07 AM
- Title changed from “[PATCH] Clean up "omg" comments” to “[Patch] has_many :through doesn't update counter_cache on join model correctly.”
- Assigned user set to “Yehuda Katz (wycats)”
- Tag changed from “3, documentation, patch, review” to “rails 3, 2-3-stable, bug, bugmash, counter_cache, has_many_through, patch”
Reverting Spam changes...
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Claudio Poli November 17th, 2010 @ 08:14 PM
I hit the same problem, using rails 2.3.

I identified another issue, look at this code:
```
class PlaylistTrack < ActiveRecord::Base
 belongs_to :playlist, :counter_cache => true, :touch => true
 belongs_to :track
```
1) adding an object to the collection using <<
- counter cache works
- playlist.updated_at fields gets correctly updated
2) **removing an object from the collection using collection.delete(object)
- counter cache won't work
- playlist.updated won't get updated
In the end there might be additional issues because Playlist might have an observer/callback that runs after_update code.

In the point 1 this after_update is not triggered by the rails code that updates the counter_cache, but from the :touch one, meaning that adding the :touch options also triggers correctly after_update callbacks.
Luckily it won't fire twice.

However in the point 2 since nothing is run also the after_update callback isn't run.

http://stackoverflow.com/questions/3902995/counter-cache-not-decrem...

Any plans to integrate this patch please?
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Claudio Poli November 17th, 2010 @ 08:18 PM
Patch is absolutely +1 for Rails 2.3, all my tests passes.
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Ivan Ukhov November 20th, 2010 @ 03:49 PM
The current status of the has_many_through association and its dependent options is the following:

https://github.com/rails/rails/blob/a3161096c287043c7f22705a771f92d...
```
        # TODO - add dependent option support
        def delete_records(records)
```
Also in the reference one can find this line:

Warning: This option is ignored when used with :through option.

I've implemented the method, and it works for me prerry well. Could anyone please test the attached patch? It turned out that it's rather hard to run the whole tests of active record...

Thanks.
- make-dependent-work-for-through-associations.patch 3.3 KB
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regis leray December 29th, 2010 @ 01:20 PM
I try with rails 3.0.4.rc or 3.1.0.beta it s still doesn't work.
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regis leray December 29th, 2010 @ 02:13 PM
I apply the path to the branch 3.0-stable (3.0.4rc)
```
class User < ActiveRecord::Base
 # need to provide an accessor , if not WARNING: Can't mass-assign protected attributes: role_ids
 attr_accessible :role_ids
 
 has_many :permissions
 has_many :roles, :through => :permissions
end

class Role < ActiveRecord::Base 
 attr_accessible :name, :users_count
 
 has_many :permissions
 has_many :users, :through => :permissions
 
end

class Permission < ActiveRecord::Base
 belongs_to :role, :counter_cache => true
 belongs_to :user
end
```
When i try to update my model (in a controller ) with

@user.update_attributes(params[:user]

i got this error

rails.3.0.4rc/activerecord/lib/active_record/relation.rb:182:in update' rails.3.0.4rc/activerecord/lib/active_record/associations/has_many_through_association.rb:95:inblock in delete_records'
rails.3.0.4rc/activerecord/lib/active_record/associations/has_many_through_association.rb:91:in each' rails.3.0.4rc/activerecord/lib/active_record/associations/has_many_through_association.rb:91:indelete_records'
rails.3.0.4rc/activerecord/lib/active_record/associations/association_collection.rb:222:in block in delete' rails.3.0.4rc/activerecord/lib/active_record/associations/association_collection.rb:525:inblock in remove_records'
rails.3.0.4rc/activerecord/lib/active_record/associations/association_collection.rb:158:in block in transaction' rails.3.0.4rc/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb:139:intransaction'
rails.3.0.4rc/activerecord/lib/active_record/transactions.rb:207:in transaction' rails.3.0.4rc/activerecord/lib/active_record/associations/association_collection.rb:157:intransaction'
rails.3.0.4rc/activerecord/lib/active_record/associations/association_collection.rb:522:in remove_records' rails.3.0.4rc/activerecord/lib/active_record/associations/association_collection.rb:221:indelete'
rails.3.0.4rc/activerecord/lib/active_record/associations/association_collection.rb:359:in block in replace' rails.3.0.4rc/activerecord/lib/active_record/associations/association_collection.rb:158:inblock in transaction'
rails.3.0.4rc/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb:139:in transaction' rails.3.0.4rc/activerecord/lib/active_record/transactions.rb:207:intransaction'
rails.3.0.4rc/activerecord/lib/active_record/associations/association_collection.rb:157:in transaction' rails.3.0.4rc/activerecord/lib/active_record/associations/association_collection.rb:358:inreplace'
rails.3.0.4rc/activerecord/lib/active_record/associations.rb:1524:in block in collection_accessor_methods' rails.3.0.4rc/activerecord/lib/active_record/associations.rb:1532:inblock in collection_accessor_methods'
rails.3.0.4rc/activerecord/lib/active_record/base.rb:1558:in block in attributes=' rails.3.0.4rc/activerecord/lib/active_record/base.rb:1554:ineach'
rails.3.0.4rc/activerecord/lib/active_record/base.rb:1554:in attributes=' rails.3.0.4rc/activerecord/lib/active_record/persistence.rb:127:inblock in update_attributes'
rails.3.0.4rc/activerecord/lib/active_record/transactions.rb:292:in block in with_transaction_returning_status' rails.3.0.4rc/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb:139:intransaction'
rails.3.0.4rc/activerecord/lib/active_record/transactions.rb:207:in transaction' rails.3.0.4rc/activerecord/lib/active_record/transactions.rb:290:inwith_transaction_returning_status'
rails.3.0.4rc/activerecord/lib/active_record/persistence.rb:126:in update_attributes' app/controllers/admin/users_controller.rb:141:inblock in update'
rails.3.0.4rc/actionpack/lib/action_controller/metal/mime_responds.rb:264:in call' rails.3.0.4rc/actionpack/lib/action_controller/metal/mime_responds.rb:264:inretrieve_response_from_mimes'
rails.3.0.4rc/actionpack/lib/action_controller/metal/mime_responds.rb:191:in respond_to' app/controllers/admin/users_controller.rb:140:inupdate'
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regis leray January 10th, 2011 @ 04:02 PM
Nobody can look into this issue i m really stuck !

Thanks in advance.

look my previous stackstrace:

rails.3.0.4rc/activerecord/lib/active_record/relation.rb:182:in update'

rails.3.0.4rc/activerecord/lib/active_record/associations/has_many_through_association.rb:95:inblock in delete_records'

rails.3.0.4rc/activerecord/lib/active_record/associations/has_many_through_association.rb:91:in each'

rails.3.0.4rc/activerecord/lib/active_record/associations/has_many_through_association.rb:91:indelete_records'

rails.3.0.4rc/activerecord/lib/active_record/associations/association_collection.rb:222:in block in delete'

rails.3.0.4rc/activerecord/lib/active_record/associations/association_collection.rb:525:inblock in remove_records'

rails.3.0.4rc/activerecord/lib/active_record/associations/association_collection.rb:158:in block in transaction'

rails.3.0.4rc/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb:139:intransaction'
Repository February 7th, 2011 @ 11:54 PM
- State changed from “open” to “resolved”
(from [52f09eac5b3d297021ef726e04ec19f6011cb302]) Correctly update counter caches on deletion for has_many :through [#2824 state:resolved]. Also fixed a bunch of other counter cache bugs in the process, as once I fixed this one others started appearing like nobody's business. https://github.com/rails/rails/commit/52f09eac5b3d297021ef726e04ec1...
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Chris Masters March 28th, 2011 @ 10:38 AM
Hi,

Apologies if this is not the correct place to post this but I would like some advice on the best way to integrate this in my project.

I am currently using rails 3.0.5 rather than rails edge.

Should I change my gemfile to point to the git repository as I am deploying to heroku.

Or is there an alternative? Perhaps cloning the git repository and manually copying the new files over?

Or do I make a patch for 3.0.5?

Apart from this functionality I am more than happy with everything else and thank you so much for all the hard work.

Sorry about this being a n00b question and if there is an FAQ or similar I have missed with this information then I apologise.

Many thanks,

Chris