calculate time difference in rails postgresql query











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I need to get time difference as query result in my rails(which has Postgres database)



Brute Force Approach



I queried all items from my database and then iterating each record and then calculating time difference in hours which is very slow.



1) @image_retouch_items = ImageRetouchItem.where(:status => '0') = Retrieved all data
2) @image_retouch_items.each do |retouch_item|
latency_date = ((Time.parse(DateTime.now.to_s) - Time.parse(retouch_item.created_at.to_s))/3600).round
end


Optimized



I need to calculate the difference of time(hours) in query itself, how to achieve that



like - ImageRetouchItem.where(:status => '0').select('(Time.parse(DateTime.now.to_s) - Time.parse(retouch_item.created_at.to_s))/3600).round')









share|improve this question


























    up vote
    0
    down vote

    favorite












    I need to get time difference as query result in my rails(which has Postgres database)



    Brute Force Approach



    I queried all items from my database and then iterating each record and then calculating time difference in hours which is very slow.



    1) @image_retouch_items = ImageRetouchItem.where(:status => '0') = Retrieved all data
    2) @image_retouch_items.each do |retouch_item|
    latency_date = ((Time.parse(DateTime.now.to_s) - Time.parse(retouch_item.created_at.to_s))/3600).round
    end


    Optimized



    I need to calculate the difference of time(hours) in query itself, how to achieve that



    like - ImageRetouchItem.where(:status => '0').select('(Time.parse(DateTime.now.to_s) - Time.parse(retouch_item.created_at.to_s))/3600).round')









    share|improve this question
























      up vote
      0
      down vote

      favorite









      up vote
      0
      down vote

      favorite











      I need to get time difference as query result in my rails(which has Postgres database)



      Brute Force Approach



      I queried all items from my database and then iterating each record and then calculating time difference in hours which is very slow.



      1) @image_retouch_items = ImageRetouchItem.where(:status => '0') = Retrieved all data
      2) @image_retouch_items.each do |retouch_item|
      latency_date = ((Time.parse(DateTime.now.to_s) - Time.parse(retouch_item.created_at.to_s))/3600).round
      end


      Optimized



      I need to calculate the difference of time(hours) in query itself, how to achieve that



      like - ImageRetouchItem.where(:status => '0').select('(Time.parse(DateTime.now.to_s) - Time.parse(retouch_item.created_at.to_s))/3600).round')









      share|improve this question













      I need to get time difference as query result in my rails(which has Postgres database)



      Brute Force Approach



      I queried all items from my database and then iterating each record and then calculating time difference in hours which is very slow.



      1) @image_retouch_items = ImageRetouchItem.where(:status => '0') = Retrieved all data
      2) @image_retouch_items.each do |retouch_item|
      latency_date = ((Time.parse(DateTime.now.to_s) - Time.parse(retouch_item.created_at.to_s))/3600).round
      end


      Optimized



      I need to calculate the difference of time(hours) in query itself, how to achieve that



      like - ImageRetouchItem.where(:status => '0').select('(Time.parse(DateTime.now.to_s) - Time.parse(retouch_item.created_at.to_s))/3600).round')






      ruby-on-rails postgresql ruby-on-rails-3 activerecord






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      share|improve this question











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      share|improve this question










      asked Nov 21 at 13:29









      summu

      4610




      4610
























          1 Answer
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          Postgres can do this for you very easily using its internal current_timestamp:



          ImageRetouchItem.where(:status => '0')
          .select("*, round(extract(epoch from(current_timestamp - created_at)) / 3600)::int as latency_date")


          current_timestamp - created_at will return an interval. By extracting epoch from that interval, we convert it to a number of seconds, which we then divide by 3600 to get hours and round using the Postgres round() function. I went ahead and casted the result as an integer using ::int, but this is optional.



          The image_retouch_item objects will now have a latency_date attribute that will contain the latency in hours, rounded to the nearest hour.






          share|improve this answer























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            1 Answer
            1






            active

            oldest

            votes








            1 Answer
            1






            active

            oldest

            votes









            active

            oldest

            votes






            active

            oldest

            votes








            up vote
            1
            down vote



            accepted










            Postgres can do this for you very easily using its internal current_timestamp:



            ImageRetouchItem.where(:status => '0')
            .select("*, round(extract(epoch from(current_timestamp - created_at)) / 3600)::int as latency_date")


            current_timestamp - created_at will return an interval. By extracting epoch from that interval, we convert it to a number of seconds, which we then divide by 3600 to get hours and round using the Postgres round() function. I went ahead and casted the result as an integer using ::int, but this is optional.



            The image_retouch_item objects will now have a latency_date attribute that will contain the latency in hours, rounded to the nearest hour.






            share|improve this answer



























              up vote
              1
              down vote



              accepted










              Postgres can do this for you very easily using its internal current_timestamp:



              ImageRetouchItem.where(:status => '0')
              .select("*, round(extract(epoch from(current_timestamp - created_at)) / 3600)::int as latency_date")


              current_timestamp - created_at will return an interval. By extracting epoch from that interval, we convert it to a number of seconds, which we then divide by 3600 to get hours and round using the Postgres round() function. I went ahead and casted the result as an integer using ::int, but this is optional.



              The image_retouch_item objects will now have a latency_date attribute that will contain the latency in hours, rounded to the nearest hour.






              share|improve this answer

























                up vote
                1
                down vote



                accepted







                up vote
                1
                down vote



                accepted






                Postgres can do this for you very easily using its internal current_timestamp:



                ImageRetouchItem.where(:status => '0')
                .select("*, round(extract(epoch from(current_timestamp - created_at)) / 3600)::int as latency_date")


                current_timestamp - created_at will return an interval. By extracting epoch from that interval, we convert it to a number of seconds, which we then divide by 3600 to get hours and round using the Postgres round() function. I went ahead and casted the result as an integer using ::int, but this is optional.



                The image_retouch_item objects will now have a latency_date attribute that will contain the latency in hours, rounded to the nearest hour.






                share|improve this answer














                Postgres can do this for you very easily using its internal current_timestamp:



                ImageRetouchItem.where(:status => '0')
                .select("*, round(extract(epoch from(current_timestamp - created_at)) / 3600)::int as latency_date")


                current_timestamp - created_at will return an interval. By extracting epoch from that interval, we convert it to a number of seconds, which we then divide by 3600 to get hours and round using the Postgres round() function. I went ahead and casted the result as an integer using ::int, but this is optional.



                The image_retouch_item objects will now have a latency_date attribute that will contain the latency in hours, rounded to the nearest hour.







                share|improve this answer














                share|improve this answer



                share|improve this answer








                edited Nov 21 at 15:03

























                answered Nov 21 at 14:48









                moveson

                3,6021426




                3,6021426






























                     

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