3 Replies Latest reply: Nov 8, 2017 7:13 AM by Jonathan Dienst RSS

    What is Faster, a Sum or a Max

    Eric Vilarrasa

      Hello, I have a question about optimisation.

       

      Suppose that my table have binary data on a dimension (0 or 1) named "IsConnected" that is telling that if someday a product is or is (1) not (0) connected, every day. If you select a period of some days (maybe it depends on the size of days you select, let's suppose that is huge) what is better to do in order to improve the efficiency of the formula:

       

      1. Sum(IsConnected)
      2. Max(IsConnected)

       

      Since it is a relational DB, I think it is easier to do a Max because QlikView have a Inner Table with the different values of the dimensions so it has only to check between two values.

       

      The second question (less important for me now) and maybe more tricky is: What if the variable is not binary?

       

      For example: Suppose that we have the number of Connected Hours of a product, in one column we have the accumualated of the connected ours ("Accum_Conected_Hours") and on the other the ours that this product has been connected this day (Daily_Conected_Hours) . What it's better in order to calculate the total hours that the product has been connected on a given period:

       

      1. Sum(Daily_Conected_Hours)
      2. Max(Accum_Conected_Hours) - Min (Accum_Conected_Hours) *

       

      * I am aware that doing a max - min may be the result is not the same but it can be fixed with a set analysis.

       

       

      Dummy data:

       

          

      DayIsConectedDaily_Conected_HoursAccum_Conected_Hours
      111010
      21515
      31823
      40023
      51427
      60027
      71532
      81840
      911050
      101555
      110055
        • Re: What is Faster, a Sum or a Max
          Jonathan Dienst

          These questions are best answered by testing on your data. It is hard to make predictions without those tests as it depends on a while lot of factors. I would expect the Max and the Sum to take a similar amount of time - but I don't see how Max() will answer the first question for you.

           

          For the second question, I would expect the second expression to be a little faster, but again you would need to test and the difference may be negligible.