3 Replies Latest reply on Feb 20, 2017 10:45 AM by Dmitry Chirkov

    What is "Parallel aggregation"?

    Dimitri Shvorob

      You see it mentioned, among other things, under "Understanding Performance optimization" on the agenda of Tableau's Qualified Associate certification exam.


      A link is provided for "Understanding Performance optimization"


      9.0 Preview: Query Performance Improvements | Tableau Software


      but I don't see anything there about "parallel aggregation", nor can I google it.

        • 1. Re: What is "Parallel aggregation"?
          Dmitry Chirkov

          See Alan Eldridge's Designing Efficient Workbooks v9.2:

          Firstly, the Tableau 9 data engine will run queries faster by using multiple cores where possible. The data engine can now run aggregations in parallel, splitting the work across multiple cores. By default, the maximum degree of parallelism is (number of available logical processors) / 2. This means that query operations on data extracts can run up to N times faster in Tableau 9 (where N is the number of cores in the machine).

          4 of 4 people found this helpful
          • 2. Re: What is "Parallel aggregation"?
            Lee Feinberg

            I may have found more information in this doc 'designing-efficient-workbooks-v10.pdf'




            Query elimination – running less queries

            You can also see in the example above that we only executed two queries instead of three. By batching the queries together, Tableau can eliminate redundant queries. Tableau’s query optimiser will sort the queries to run the most complex queries first in the hope that subsequent queries can be serviced from the result cache. In the example, because the timeline includes Product Category and because the SUM aggregation of Sales Amount is fully additive, the data for the Category chart can be resolved from the query cache of the Timeline worksheet and doesn’t require a hit on the data source.

            The query optimiser will also look for queries that are at the same level of detail (i.e. they are specified by the same set of dimensions) and will collapse them into a single query that returns all requested measures. Consider the following dashboard:

            • 3. Re: What is "Parallel aggregation"?
              Dmitry Chirkov

              No, "parallel aggregation" is a Tableau Data Engine's feature.

              What you a referring above we call internally "query fusion" - something we introduced alongside with parallel query execution and can be applied to any data source type.