Adding Zeros

active_record_ext.rb

# I was dealing with a number of different log methods (per minute, per hour, per day) etc
# Where times with no data were not stored in the database. This was an attempt at getting active record to
# inject zeroed data into to the returned datasets. 
#
# It worked, but the experiment was a failure:
# 1) extracting times from the where_values is brittle and will fail often
# 2) It gets applied to all AR models
# 3) It required adding two methods (new_default and period) to the corrospoding AR classes creating too strong coupling


class ActiveRecord::Relation

  def with_zeros
    start_date = Date.parse(where_values.first.split("'")[1])
    end_date   = Date.parse(where_values.first.split("'")[3])
    puts "Creating values between #{start_date} and #{end_date}"
    
    start_time = Time.utc(start_date.year, start_date.month, start_date.day)
    end_time = Time.utc(end_date.year, end_date.month, end_date.day)
    puts "We are working with #{self.klass.name} data"
    puts "First timestamp is #{start_time.to_time}"
    puts "Last timestamp is #{end_time.to_time}"
    
    #Note we assume that this is sorted
    data_without_zeros = self.all
    data_with_zeros = []
    
    t = start_time
    next_index = 0
    while t < end_time
      if(data_without_zeros[next_index] && (data_without_zeros[next_index].created_at == t))
        data_with_zeros << data_without_zeros[next_index]
        next_index += 1
      else
        data_with_zeros << self.klass.new_default(t)
      end
      t = t + self.klass.period
    end
    
    data_with_zeros
  end
end