Ruby on Rails counter cache error

Question

I get the error Unknown key(s): counter_cache when trying to implement a counter cache column in my RoR app.

I implemented the model associations in this question: Model association question

Here's my migration:

class AddVideoVotesCountToVideos < ActiveRecord::Migration
  def self.up
    add_column :videos, :video_votes_count, :integer, :default => 0

    Video.reset_column_information
    Video.find(:all).each do |p|
      p.update_attributes :videos_votes_count, p.video_votes.length
    end
  end

  def self.down
    remove_column :videos, :video_votes_count
  end
end

However, after watching http://media.railscasts.com/videos/023_counter_cache_column.mov I thought that maybe I had to move :counter_cache => true into the VideoVote model after belongs_to :video. However, when I do that, I get the error:

wrong number of arguments (2 for 1)

What am I doing wrong?

Leninism

Answer 1

update_attribute not update_attribteS

p.update_attribute :videos_votes_count, p.video_votes.length

or with update_attributes:

p.update_attributes( :video_votes_count => p.video_votes.length )

UPD 1

:counter_cache => true should be at the VideoVote class:

class VideoVote < ActiveRecord::Base
  belongs_to :user
  belongs_to :video, :counter_cache => true
end

Feudist

still get the first error... where should :counter_cache => true go? – Leninism

ok, now I get this error: undefined method 'videos_votes_count=' for #<Video:0x10362a698> – Leninism

you use update_attributes or update_attribute? Also you can temprory remove counter_cache => true because it obviously locks field – Feudist

What method do you use, which one update_attributes or update_attribute ? :) and remove counter_cache => true for a while, do your migrate and return it back :) – Feudist

ahh ok yeah, that solved it, I needed to take out counter_cache, migrate, and then return it back... thanks! – Leninism

Answer 2

To do counter_caching,you need to run the migration first that fills in the count columns BEFORE you include the counter_cache statement in the model. Once in the model, the columns are read only.

Greysun

Answer 3

To avoid read-only errors while running this migration, you should use reset_counters:

Video.find_each do |video|
  Video.reset_counters video.id, :video_votes
end

Roundhouse

The second argument to the reset_counters method needs to be the name of the association, not the name of the counter_cache column, so it should be: Video.reset_counters video.id, :video_votes – Flurried

reset_counters is now deprecated – Typescript

@gwho I think it's still there... github.com/rails/rails/blob/master/activerecord/lib/… – Roundhouse

Answer 4

Rewriting Rajive Jain's solution :

Remove :counter_cache => true statement from the model file.

Rerun the migration : rake db:migrate

Add the counter_cache statement in your model : :counter_cache => true

Orton