MQL Query

Owned by Former user (Deleted)
Last updated: Mar 17, 2011 by Former user (Deleted)Version comment
2 min read

Description

Uses the Pentaho Metadata Query Language (MQL) to perform a query against Pentaho Metadata.

Inputs and Outputs

MQL - The MQL query to be performed.

Output Name - The name of the resulting output dataset. Following actions can refer to the data set using this name.

MQL Designer

The MQL Designer facilitates the authoring of MQL through the use of a simple to use UI. In order to use the MQL Designer from within the design studio, the action sequence being edited must reside inside a valid pentaho solution. At the root of the solution there must exist a metadata.xmi file that is properly configured.

MQL Preview

The MQL Preview button allows the user to preview the data that will be returned from the MQL Query. For preview to work, the JDBC driver jar file for the database you are trying to use must be in the plugin classpath. To add a new JDBC driver to your plugin classpath, follow these steps:

  1. The driver jar for your RDBMS should be dropped into the <eclipse_install_directory>/plugins/org.pentaho.designstudio.editors.actionsequence_x.x.x/lib directory.
  2. Next edit, <eclipse_install_directory>/plugins/org.pentaho.designstudio.editors.actionsequence_x.x.x/META-INF/MANIFEST.MF and add your driver jar name and location to the bundle classpath. The entry may look like this: lib/mydriver.jar,
  3. Note that if you are modifying an existing Pentaho action sequence plugin already deployed and used in Eclipse, you may need to remove the plugin, start and stop Eclipse, re-deploy the plugin and make the necessary driver changes BEFORE starting Eclipse again. It seems there are some caching issues in Eclipse that prevents Eclipse from recognizing the MANIFEST file changes if the action sequence plugin was used previously.

If the metadata model that the query is run against uses a JNDI connection definition (a named JNDI datasource), then you must modify the simple-jndi settings in your pentaho-solutions project to include the JNDI name that your model references.

  1. Navigate in your pentaho-solutions to the pentaho-solutions/system/simple-jndi/jdbc.properties.
  2. Open this file, and following the format you see there for a database connection definition, add your JNDI connection information.

Once this is done MQL queries can be previewed.