5 Replies Latest reply on Apr 23, 2019 8:18 AM by Martin Sellers

    System Error: Null

    Martin Sellers

      I am getting this error message when using the center output.  "system error: null"

      This flow was working previously.  I updated a few of the early steps and added the union.  Since then I have been getting the error.


      To get around this, I right clicked the step before my output and chose to "preview in tableau" and the data exported to tableau fine.   I then exported the data to csv from Tableau to continue my work.

      The other two outputs in the flow seem to work fine.


      Any idea what's going on?


        • 1. Re: System Error: Null
          Michael Enck

          I often get this error when the Tableau Desktop file is still open.

          • 2. Re: System Error: Null
            Rob Palmer

            I've been having the same error. However, if I tell it to publish directly to Tableau server it works fine. Just seems to be exports to disk that are causing it.

            • 3. Re: System Error: Null
              Egor Larin

              I have the similar issue.


              Do you have any STR to INT or INT to STR transformation?


              I found if you use  field that was transformed to STR (original field is INT) in JOINS output just after JOIN stopped working.

              After removing INT->STR transformation -  the whole flow is started working.


              Try to define on which step you have failing output. Basically, you can run output from any 'block' to troubleshoot it:



              Found that issue here:

              Prep: System error: null


              And issue #783920 from the Release Notes. Not sure if that relates to the issue.

              After joining a .csv file with a MySQL table, the following error occurred, when publishing the .hyper file to Tableau Online/Tableau Server:

              "Collation mismatch, use COLLATE statements to resolve."


              In the logs I can see the errors:

              com.tableau.loom.exceptions.OutputNodeFailureException: Unable to process output step: Failure evaluating to database: ERROR:  collation mismatch, use COLLATE statements to resolve


              TID:pool-3-thread-4 DOC_ID:888fdaaf-ca04-4cc6-8cb5-5407fb087466 REQ_ID:43a9d1f8-9770-4287-8a31-ddbf2b1accef LVL:ERROR CLASS:com.tableau.loom.runtime.SelectIntoExecutor MSG:Error processing selectInto

              2 of 3 people found this helpful
              • 4. Re: System Error: Null
                Rob Palmer

                Thanks Egor. This was exactly my issue. In the end I took the calculation out of Prep and moved it into my Tableau workbook and it resolved the issue.Must be to do with the way the evaluation process changes after the first run. I was finding that the issue would only present itself on refresh and if I rebuilt my prep package it would work fine.

                • 5. Re: System Error: Null
                  Martin Sellers

                  Rob -

                  If you do want to keep that calculation in your flow rather than moving it to the workbook - when you identify the step that is causing the issue - use the necessary STR() or INT() functions in calculated field(s) before every variable (that you want type changed) throughout the step.  Often this solves the issue.