find each by column

find_each_by_column.rb

class ActiveRecord::Base
  def self.find_each_by(column, options={}, &block)
    return enum_for(:find_each_by_column) unless block_given?
    
    last_value = last_id = nil    
    order = options.fetch(:order, :asc)
    batch_size = options.fetch(:batch_size, 1000)
    operator = order == :asc ? '>=' : '<='
    
    loop do
      relation = all
      relation = relation.order("#{column}, id #{order}")
      relation = relation.where("#{column} #{operator} ?", last_value) if last_value
      relation = relation.where("id #{operator[0]} ?", last_id) if last_id
      relation = relation.limit(batch_size)
      results = relation.to_a
      
      break if results.empty?
      results.each(&block)
      last_value = results.last.send(column)
      last_id = results.last.id
    end
  end
end