gistfile1.rb

  def self.query_benchmark
    keys = Visit.column_names
    total = Visit.count
    Benchmark.bm(7) do |x|      
      # 346.010000   1.380000 347.390000 (357.346086)      
      # 361.920000   1.650000 363.570000 (417.746442)      
      x.report("ActiveRecord") do  
        Visit.find_in_batches(:batch_size => 5000) do |visits|
          visits.map{|v| keys.map{|k| v.send(k.to_sym)}}
        end
      end

      # 1613.550000   6.760000 1620.310000 (1667.230748)
      x.report("ActiveRecord json") do
        Visit.find_in_batches(:batch_size => 5000) do |visits|
          visits.to_json
        end
      end

      # 58.640000   0.780000  59.420000 ( 67.759693)
      # 64.520000   0.920000  65.440000 (142.426560)
      x.report("Pure") do
        primary_key_offset = 0  
        begin 
          sql = "SELECT * FROM `visits` WHERE (id > #{primary_key_offset}) ORDER BY `id` ASC LIMIT 5000"
          rows = ActiveRecord::Base.connection.execute(sql)
          primary_key_offset = rows.to_a.last[rows.fields.index("id")] if rows.any?
        end while rows.any?
      end
      
      # 74.600000   1.380000  75.980000 ( 85.274206)
      fields = ReportingSerializerConfig[:all].reverse_merge(ReportingSerializerConfig[:schemas]['Visit']).to_a.map{|field| field.join(' as ')}.join(', ')
      x.report("Pure") do
        primary_key_offset = 0  
        begin           
          sql = "SELECT #{fields} FROM `visits` WHERE (id > #{primary_key_offset}) ORDER BY `id` ASC LIMIT 5000"
          rows = ActiveRecord::Base.connection.execute(sql)         
          data_array = rows.to_a(:as => :hash)
          primary_key_offset = data_array.last["mysql_id"] if data_array.any?        
        end while data_array.any?
      end
    end
  end