KNOWLEDGE BASE

Additional Queries are Sent to the Database When Opening Workbooks that Use "Only Relevant Values" Filters


Published: 14 Mar 2016
Last Modified Date: 20 Mar 2017

Issue

When loading a view using quick filters with the "Only relevant values" option enabled, Tableau Desktop sends additional queries to the database after the dashboard was loaded.

The queries are similar to the following:
SELECT CAST(COUNT(DISTINCT "dimension") AS BIGINT) AS "dimension_alias"
        FROM "database"."table" "table_alias"
         ... //more SQL here
        GROUP BY ()

Environment

Tableau Desktop 8.0.4 and later

Resolution

These queries are part of the "acceleration views" feature.

Cause

The purpose of this feature is to speed up subsequent quick filter interactions. Tableau Desktop tries to pre-compute relevant values quick filters and these queries in particular only serve the purpose of determining the full size (number of distinct values) of the quick filters.

​As these values are not relevant for the initial load of the view, Tableau Desktop sends them out after the view has been computed in an attempt to reduce computation time of further quick filter selections.

Additional Information

Occasionally the acceleration views feature leads to performance loss. In this case a TDC option can be used to turn off the feature (Release notes 8.0.4):

Added a new TDC option: CAP_SUPPRESS_QUICK_FILTER_ACCELERATION_VIEWS. This option prevents Tableau from issuing queries to construct acceleration views for relative values quick filters. This option can be used in cases where product performance was degraded when using quick filters. See Knowledge Base article Customizing ODBC Connections for more information on using TDC files
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