how to get unvoted post count in Ruby on Rails - ruby-on-rails

Question

I am using Thumbs_up gem for creating vote function. I have 3 tables - Post, User and Vote where Post is acts_as_voteable and User is acts_as_voter.
Model Post.rb
class Post < ActiveRecord::Base
attr_accessible :title, :content, :user_type
acts_as_voteable
validates_presence_of :title,:content
default_scope order: 'posts.created_at DESC'
end
Model Vote.rb
class Vote < ActiveRecord::Base
scope :for_voter, lambda { |*args| where(["voter_id = ? AND voter_type = ?", args.first.id, args.first.class.base_class.name]) }
scope :for_voteable, lambda { |*args| where(["voteable_id = ? AND voteable_type = ?", args.first.id, args.first.class.base_class.name]) }
scope :recent, lambda { |*args| where(["created_at > ?", (args.first || 2.weeks.ago)]) }
scope :descending, order("created_at DESC")
belongs_to :voteable, :polymorphic => true
belongs_to :voter, :polymorphic => true
attr_accessible :vote, :voter, :voteable
end
Model User.rb
class User < ActiveRecord::Base
attr_accessible :name, :email, :password, :password_confirmation
has_secure_password
acts_as_voter
has_many :posts, dependent: :destroy
end
Now I want to count posts number which are NOT VOTED. I am trying to do like this..
<%= Post.joins(:votes).where("dont_know_how_to_write_condition").count %>
Any help?? Thanks in advance

Answer 1

I am not sure if this will work in sqlite, it should on postgresql though.
def self.not_voted
joins("left outer join votes on votes.voteable_id = posts.id").
where("votes.id is null")
end
Then:
Post.not_voted.count

Answer 2

There are ways to do that condition in SQL with NOT EXISTS but they are very heavy queries. If this si going to be an action facing the public or performed multiple times, it might be too heavy to do it like that. I would recommend you to denormalize the tables and include a count of votes on the post. Just use an observer on vote creation and deletion to update the vote count for the post. The query then would be like
Post.where('votecount = 0')
This query is much lighter and scalable than the previous one