Configuring Parallel Queries in Tableau Desktop

Tableau Desktop can initiate multiple, parallel connections automatically when communicating with a data source. You can specify any and all of the following:

• A global limit on the number of parallel queries for Tableau Desktop
• Limits for a particular data source type, such as SQL Server
• Limits for a particular data source type on a specific server
• Limits for a particular data source type, on a specific server, when connecting to a specific database
• Limits for how many data sources can be queried simultaneously in a cross-database join

These settings are managed by an xml file named connection-configs.xml which you create and save in the Tableau Desktop folder. The default locations are:

• On a Windows computer: C:\Program Files\Tableau\Tableau <Version>
• On a Mac: The folder location is Applications/Tableau.app/Content. To access this folder from Finder, navigate to the Tableau application, press Control+Click, and choose Show Package Content.

<?xml version='1.0' encoding='utf-8' ?> 
<connection-list> 
<connection class='sqlserver' dbname='SalesDB' server='SQLserver10'> 
    <limit max='10'> 
    </limit> 
</connection> 
<connection class='mysql' dbname='Inventory' server='MySQL_Public'> 
    <limit max='10'> 
    </limit> 
</connection> 
<connection class='teradata' schema='TravelData' server='TeradataProduction2'> 
    <limit max='12'> 
    </limit> 
</connection> 
<connection class='sqlserver'> 
    <limit max='4'> 
    </limit> 
</connection> 
<connection class='mysql'> 
    <limit max='6'> 
    </limit> 
</connection> 
<connection class='teradata'> 
    <limit max='10'> 
    </limit> 
</connection> 
<connection> 
    <limit max='8'> 
    </limit> 
</connection> 
</connection-list> 

Set a Global Limit

A <connection> tag with no information about data source type, server, or database defines the maximum number of queries for all connections not covered by any other, more specific, connection specification. For example:

   <connection>
      <limit max='8'>
      </limit>
   </connection>

This value overrides the default parallel query limit, which is 16 for all data sources types except Amazon Redshift (for which the default is 8).

Set Additional Limits

Connection settings in connection-configs.xml can work at different levels of specificity. When establishing a connection, Tableau parses the file from top to bottom, so if there is more than one entry that would apply to a given connection, the entry nearest the top of the file is used.

For this reason, it is also appropriate to order connection specifications from most specific to least specific.

Additional (non-global) limits are set in a <connection-list> section at the top of the connection-configs.xml file.

The parameters you can use in a <connection> tag are:

You can specify parameters in any order and any combination—for example, you could specify a server and a dbname without specifying a class.

Class Strings

Use the following strings to identify data source types in connection-configs.xml.

Logging

• When the connections are matched to entries in connection-configs.xml, Tableau logs the connection limit for debugging purposes.