Cloudera Hadoop

This topic describes how to connect Tableau to a Cloudera Hadoop database and set up the data source. Refer to the Connecting to Cloudera Hadoop knowledge base article for more details about connecting to Hadoop data.

1. Click Connect to Data.
   
2. On the Connect page, click Cloudera Hadoop, and then do the following:
   
   1. Type the name of the server that hosts the database and the port number to use. If you are connecting using Impala you must use port 21000. This is the default port if you are using the 2.5.x driver (recommended).
      
   2. Select how to connect to the database. Depending on the version of Hadoop and the drivers you have installed, you can connect using one of the following:
      
      • Hive Server
        
      • Hive Server 2
      • Impala
      Note: For secure connections to Cloudera Hadoop, it is recommended that you use Hive Server 2. See Connecting to Hive server 2 in Secure Mode.
   3. Click Connect.
      If the connection is unsuccessful, verify that your user name and password are correct. If the connection continues to fail, your computer is having trouble locating the server. Contact your network administrator or database administrator.
      
3. On the data source page, do the following:
   
   1. (Optional) Click the default data source name at the top of the page, and then type a unique data source name for use in Tableau.
      
   2. From the Schema drop-down list, type the schema name in the text box, click the search icon, and then select the schema.
      
   3. Type the table name in the Table text box, click the search icon, drag the table to the join area, and then click Go to Worksheet to begin building the view. Alternatively, drag additional tables to the join area and use conditions to join them. You can choose to combine tables or use Custom SQL when you are working with multiple tables. You can also add joins later.
      Optionally, you can make the following configurations before building the view:
      
      • Preview the data – In the preview area, select Update Now to preview the first 10,000 rows of the data source. If you add tables, remove tables, or make changes to the join conditions, click Update Now. If you want changes to automatically reflect in the preview area, click Automatically Update.
        
      • Change data types – Change the data type of a column by clicking the data type icon.
        
      • Rename or hide columns – Rename or hide a column by clicking the column header drop-down menu and selecting the respective option.
        
      • Connect live or use an extract – At the top of the data source page, select a live or extract connection to the data source. If you choose to take an extract, an Edit link displays allowing you to set up filters that define a subset of the data to include in the extract.
        
      • Add data source filters – Add data source filters to restrict the visibility and use of the fields in the data source.
        

Initial SQL

When connecting to Cloudera Hadoop, you can optionally specify a SQL command that will be run once upon connection. See Initial SQL to learn more about adding these commands to your connection.

Hadoop and Impala

When connecting to Hadoop using Impala, the queries are limited to 100,000 rows of data when the query includes an ORDER BY clause. This limit can be configured either by modifying the "order-by-limit" value in the workbook xml or using a TDC customization such as <customization name="order-by-limit" value='10' />.

An example of a Cloudera Hadoop data source is shown below.