3 Replies Latest reply on Jul 6, 2018 3:26 PM by Deepak Rai

    Joining multiple tables becomes extremely slow

    Siebe Bosch

      Dear community,


      I have a geographic file (shapefile) that constists of around 40 polygons
      I have an Excel-document that has several tabpages, each containing a few hundred records.


      The process of joining tables however is extremely slow and it looks like the time required grows exponentially with the number of joins I create.


      In 8 Excel tabpages I have data that refers to the polygons in the shapefile.
      So I try to create 8 joins between the geographic data source and the excel tab page. Like so:




      The problem is: after the third join the whole process becomes so slow that Tableau becomes non-responsive for a long time.
      Only after the process has finished am I allowed to change the join type from an inner join to a left join (which appears to be a LOT faster).


      An example of the data:


      Geographic file contains polygons, each of which has an ID in the field owmident. Here's one of them, displayed on top of Openstreetmap.



      The Excel file, e.g. the tab ESF1.Score contains water quality values for each of the polygons:



      Question: is there a smarter way to import this data? For starters, I do not need any interaction between data on the various Excel-sheets. So is it really necessary for Tableau to create some sort of huge internal table that contains mililons of unique combinations of my records?


      In stead of this:


      I would much rather have had something like this:


      Is this even possible in Tableau? Or are there better ways to prepare my data for Tableau?


      Thanks for your ideas.