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Starting Hive-Client Programmatically With Scala

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Starting Hive-Client Programmatically With Scala

Learn about using Scala with Hive for programmatic access to Hadoop data.

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Hive defines a simple SQL-like query language for querying and managing large datasets called Hive-QL (HQL). It’s easy to use if you’re familiar with SQL Language. Hive allows programmers who are familiar with the language to write the custom MapReduce framework to perform more sophisticated analyses.

In this blog, we will learn how to create a Hive client with Scala to execute basic HQL commands. First, create a Scala project with Scala 2.12 version.

Now, add the following properties in your build.sbt file:

name := "hive_cli_client"
version := "1.0"
scalaVersion := "2.12.2"
libraryDependencies += "org.apache.hive" % "hive-exec" % "1.2.1" excludeAll
                       ExclusionRule(organization = "org.pentaho")

libraryDependencies += "org.apache.hadoop" % "hadoop-common" % "2.7.3"
libraryDependencies += "org.apache.httpcomponents" % "httpclient" % "4.3.4"
libraryDependencies += "org.apache.hadoop" % "hadoop-client" % "2.6.0"
libraryDependencies += "org.apache.hive" % "hive-service" % "1.2.1"
libraryDependencies += "org.apache.hive" % "hive-cli" % "1.2.1"
libraryDependencies += "org.scalatest" % "scalatest_2.12" % "3.0.3"

In my case, I am using Hive 2.1.1; you can use any. Let the dependencies be resolved. Now, add a Scala class in your project named hiveclient:

package cli

import java.io.IOException

import scala.util.Try

import org.apache.hadoop.hive.cli.CliSessionState
import org.apache.hadoop.hive.conf.HiveConf
import org.apache.hadoop.hive.ql.Driver
import org.apache.hadoop.hive.ql.session.SessionState

/**
 * Hive meta API client for Testing Purpose
 *
 * @author Anubhav
 */
class HiveClient {

  val hiveConf = new HiveConf(classOf[HiveClient])

  /**
   * Get the hive ql driver to execute ddl or dml
   *
   * @return
   */
  private def getDriver: Driver = {
    val driver = new Driver(hiveConf)
    SessionState.start(new CliSessionState(hiveConf))
    driver
  }

  /**
   * @param hql
   * @throws org.apache.hadoop.hive.ql.CommandNeedRetryException
   * @return int
   */

  def executeHQL(hql: String): Int = {
    val responseOpt = Try(getDriver.run(hql)).toEither
    val response = responseOpt match {
      case Right(response) => response
      case Left(exception) => throw new Exception(s"${ exception.getMessage }")
    }
    val responseCode = response.getResponseCode
    if (responseCode != 0) {
      val err: String = response.getErrorMessage
      throw new IOException("Failed to execute hql [" + hql + "], error message is: " + err)
    }
    responseCode
  }

}

It has one public method, executeHQL, that calls the private method getDriver to get the hiveDriver instance and execute HQL with it. This method will give back the response code back.

Now, write the test case to test this Hive client:

import cli.HiveClient
import org.scalatest.FunSuite

class HiveClientTest extends FunSuite {

  val hiveClient = new HiveClient

  test("testing for the hql query") {
    assert(hiveClient.executeHQL("DROP TABLE IF EXISTS DEMO") == 0)
    assert(hiveClient.executeHQL("CREATE TABLE IF NOT EXISTS DEMO(id int)") == 0)
    assert(hiveClient.executeHQL("INSERT INTO DEMO VALUES(1)") == 0)
    assert(hiveClient.executeHQL("SELECT * FROM DEMO") == 0)
    assert(hiveClient.executeHQL("SELECT COUNT(*) FROM DEMO") == 0)

  }

}

Now, run these test cases:

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Topics:
scala ,big data ,hadoop ,hive ,tutorial

Published at DZone with permission of Anubhav Tarar, DZone MVB. See the original article here.

Opinions expressed by DZone contributors are their own.

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