0 Replies Latest reply on Feb 18, 2014 10:55 AM by Rich Wask

    Query Performance - Using a Calculation field in another calculated field

    Rich Wask

      Are there performance issues if you use a calculated field in another calculated field, and then use the newly created calculated field in a Filter?

      Ex.  I do a positive and negative record count calculation (by reading all of the records for each subject).  I then created another calculation field that uses the nagative and positive counts (for each subject)  to find the greatest percentage of negative to positive records.  i.e. negating count / (negative count + positive count)

      I then use the newly created calculated percentage field in the filter, to get the subjects that have a greater then 50% negative records (using the Filter scale), sort them by greatest percentage, and plot them on a Map (I have each subjects Lat./Long.).

      I let this query run for over an hour and it does not finish.

       

      I do not know how Tableau performs its queries and rendering(sequence of events) that have Filters and Calculated fields, and am wondering if I need to be careful how I create my calculations and filtering.

       

      Could someone who definitvely knows, explain the order of precedence and how Tableau handles Calculated fields, Filters, and Calculated fields used in a Filter?   Is this documented online or something I can view or read about online?

       

      Okay, there are actually three questions here.

      1. Performance issue?
      2. Tableau's order of precedence for Calculations, Filters, and rendering?
      3. Is there documentation or video on, "Tableau's order of precedence for Calculations, Filters, and rendering"?

       

      Thank you in advance for your time in viewing and answering this.