How to work with HDFS Data in Apache Spark using SQL

Apache Spark is a fast and general engine for large-scale data processing. When paired with the CData JDBC Driver for HDFS, Spark can work with live HDFS data. This article describes how to connect to and query HDFS data from a Spark shell.

The CData JDBC Driver offers unmatched performance for interacting with live HDFS data due to optimized data processing built into the driver. When you issue complex SQL queries to HDFS, the driver pushes supported SQL operations, like filters and aggregations, directly to HDFS and utilizes the embedded SQL engine to process unsupported operations (often SQL functions and JOIN operations) client-side. With built-in dynamic metadata querying, you can work with and analyze HDFS data using native data types.

Install the CData JDBC Driver for HDFS

Download the CData JDBC Driver for HDFS installer, unzip the package, and run the JAR file to install the driver.

Start a Spark Shell and Connect to HDFS Data

1. Open a terminal and start the Spark shell with the CData JDBC Driver for HDFS JAR file as the jars parameter: $ spark-shell --jars /CData/CData JDBC Driver for HDFS/lib/cdata.jdbc.hdfs.jar
2. With the shell running, you can connect to HDFS with a JDBC URL and use the SQL Context load() function to read a table.

   In order to authenticate, set the following connection properties:

   • Host: Set this value to the host of your HDFS installation.
   • Port: Set this value to the port of your HDFS installation. Default port: 50070

   Built-in Connection String Designer

   For assistance in constructing the JDBC URL, use the connection string designer built into the HDFS JDBC Driver. Either double-click the JAR file or execute the jar file from the command-line.

   java -jar cdata.jdbc.hdfs.jar

   Fill in the connection properties and copy the connection string to the clipboard.

   Configure the connection to HDFS, using the connection string generated above.

   scala> val hdfs_df = spark.sqlContext.read.format("jdbc").option("url", "jdbc:hdfs:Host=sandbox-hdp.hortonworks.com;Port=50070;Path=/user/root;User=root;").option("dbtable","Files").option("driver","cdata.jdbc.hdfs.HDFSDriver").load()
3. Once you connect and the data is loaded you will see the table schema displayed.

4. Register the HDFS data as a temporary table:

   scala> hdfs_df.registerTable("files")

5. Perform custom SQL queries against the Data using commands like the one below:

   scala> hdfs_df.sqlContext.sql("SELECT FileId, ChildrenNum FROM Files WHERE FileId = 119116").collect.foreach(println)

   You will see the results displayed in the console, similar to the following:

Using the CData JDBC Driver for HDFS in Apache Spark, you are able to perform fast and complex analytics on HDFS data, combining the power and utility of Spark with your data. Download a free, 30 day trial of any of the 200+ CData JDBC Drivers and get started today.