How to connect to Jethro from Denodo

Applies to: Denodo 7.0
Last modified on: 16 Aug 2019
Tags: Jethro JDBC data sources

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Goal

This document describes on how to connect to Jethro from the Denodo Platform.

Jethro is a middleware software that resides between BI clients and underlying Hadoop or AWS clusters.

From Denodo, we can retrieve data from Jethro by creating a JDBC data source using Jethro’s JDBC Driver.

Connecting to Jethro from Denodo

  1. First, download Jethro’s JDBC driver from https://jethro.io/driver-downloads and copy the driver jar file to the folder <DENODO_HOME>/lib-external/jdbc-drivers/jethro-<x.x>
  2. From the Denodo Virtual DataPort Administration Tool, create a new JDBC data source by choosing File > New > Data Source >JDBC. This will open a wizard to create a connection to a data source with a JDBC driver.

  1. To establish a connection, fill the following fields:
  • Name: ds_jethro
  • Database adapter: Generic
  • Driver class path: Point to the path where you have saved the driver.
  • Driver class: com.jethrodata.JethroDriver
  • Database URI: Use a connection string in the form of: jdbc:JethroData://<server>:<port>/<schema>
  • Authentication: Choose the authentication type to connect to Jethro
  • Login and Password - Enter the credentials to access Jethro server.

      3. Click Test Connection. If the test is successful, click Save.

     4. Source Configuration:

Jethro does not support Prepared statements. Therefore, set Allow Literal as Parameter to No in the Source Configuration tab of the data source.

In addition to that implicit joins are not supported, the join condition must be explicit to make it work. To configure this set Supports Explicit CROSS JOIN and Supports JOIN ON condition to Yes.

Change the value of the following properties in the Source Configuration of the data source and save the view

Source Configuration Property

Value

Allow Literal as Parameter

No

Supports Explicit CROSS JOIN

Yes

Supports JOIN ON condition

Yes

Note:

In some situations, the data retrieval may be slow when trying to access large data sets. In order to improve the performance, try to increase the value of the Fetch size parameter in the Data Source Configuration based on your requirements.

This property will give a hint to the JDBC driver about the number of rows that should be fetched from the database when more rows are needed. By default the value of this property is 1000 rows.

Creating Base Views

On these changes are done, click on the Create base view tab to introspect source metadata available through the Data Source. Select the views you want to create a base view over and then, click the Create selected.

Query the base view to start retrieving data from Jethro

References

JDBC Sources

Data Source Configuration Properties

Jethro Documentation

Questions

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