Review: Daily Votes

[georgiee]

Hi Brady,
thank you for this great work. I appreciate it!

I just changed thumbs_up to a daily voteable version. It`s to less for a pull req but maybe useable for someone.
I added a new index field to hold only the day and used this field as a member of the validate scope and also inside the pg fk. WIll this have any impact on the tally performance or performance in general ?

this is the migration

class AddIndexVotesForDailyVoters < ActiveRecord::Migration
  def change
    #remove old fk we replace it with another version below
    remove_index :votes, :name => "fk_one_vote_per_user_per_entity"
    #add indexable field with day values- no hours, minutes or seconds
    add_column  :votes, 
                :day_created_at,
                :timestamp
    #add the new index additionally based on day_created_at
    add_index   :votes,
                ["voter_id", "voter_type", "voteable_id", "voteable_type", "day_created_at"], 
                :name => "fk_one_vote_per_user_per_entity_per_day", 
                :unique => true
  end
end

and that`s the part in vote.rb

class Vote < ActiveRecord::Base
 #...
  #day_created_at
  validates_uniqueness_of :voteable_id, :scope => [:voteable_type, :voter_type, :voter_id, :day_created_at]
  #added
  before_create :record_day_created_at
  def record_day_created_at
    self.day_created_at=DateTime.now.utc.midnight
  end
end

[georgiee]

Well, I just realized that the method voted_for? can`t be used for a daily voting. I created another method "voted_for_today?" for this.

config/initializers/thumbs_up.rb

module ThumbsUp
  module ActsAsVoter
    module InstanceMethods
      def voted_for_today?(voteable)
        0 < Vote.where(
          :voter_id => self.id,
          :voter_type => self.class.base_class.name,
          :voteable_id => voteable.id,
          :voteable_type => voteable.class.base_class.name,
          :day_created_at => DateTime.now.utc.midnight
        ).count
      end
    end
  end
end

[bouchard]

Looks good! Feel free to add it to the Wiki for anyone else that might like to make a similar adaptation.

[bouchard]

And to answer your question, shouldn't have any impact on vote tallying, as you've indexed it correctly.

[turadg]

@bouchard I have a similar addition for the wiki, but when I click the Wiki tab it redirects to the Code tab. Is the wiki enabled on this repo? Does it need a starter page?

[bouchard]

Should be good now, apparently I needed to visit it once for it to be created. Let me know if it works!

[turadg]

yup! added my example and @georgiee 's

[georgiee]

I also wondered about the wiki but I had not the time for asking yet. It works now. Thanks for adding turadg!

[boska]

thanks bouchard and georglee for the great work and modify !

apply this perfectly on my work , but if i want to make a "one vote per 5min version" , can you show me some direction. sorry for my poor english and rails skill

[georgiee]

Hi boska,
you should be able to accomplish this by changing DateTime.now.utc.midnight to another discrete value representing your timeslot.

For example the following function gives you the nearest time rounded to 5 minutes:

#generate a 5min time slot 
Time.at((Time.now.to_f/300).round * 300)
#2013-01-08 08:35:00 +0100
#2013-01-08 08:40:00 +0100
#2013-01-08 08:45:00 +0100

I think you have to ensure that the generated "time slot" is always ceiling. Simple rounding could be able problem in the edge cases where a user voted just before the next time slot. For example vote A in 00:04:59 and vote B in 00:05:01. If the time slot calculation is wrong the user could be able to make vote B after two seconds. Because of the involved rounding you will hardly get a perfect 5 minute window. If this is important in your use case you need to develop another solution and I guess without involving the fast index based distinction.

Regards George

[boska]

thanks for the advise , i may apply this concept first , and try out for the best accuracy time slot soultion.