Hive dialect in Apache Flink® clusters on HDInsight on AKS

In this article, learn how to use Hive dialect in Apache Flink clusters on HDInsight on AKS.

Introduction

The user can't change the default flink dialect to hive dialect for their usage on HDInsight on AKS clusters. All the SQL operations fail once changed to hive dialect with the following error.

*java.lang.ClassCastException: class jdk.internal.loader.ClassLoaders$AppClassLoader can't be cast to class java.net.URLClassLoader*

The reason for this issue arises due to an open Hive Jira. Currently, Hive assumes that the system class loader is an instance of URLClassLoader. In Java 11, this assumption isn't the case.

How to use Hive dialect in Flink

• Execute the following steps in webssh:

  1. Remove the existing flink-sql-connector-hive*jar in lib location

     rm /opt/flink-webssh/lib/flink-sql-connector-hive*jar
     

  2. Download the following jar in webssh pod and add it under the /opt/flink-webssh/lib wget https://aka.ms/hdiflinkhivejdk11jar. (The above hive jar has the fix https://issues.apache.org/jira/browse/HIVE-27508)

  mv /opt/flink-webssh/lib/flink-table-planner-loader-1.17.0-*.*.*.*.jar /opt/flink-webssh/opt/
  mv /opt/flink-webssh/opt/flink-table-planner_2.12-1.17.0-*.*.*.*.jar /opt/flink-webssh/lib/
  

  1. Add the following keys in the flink configuration management under core-site.xml section:

     fs.azure.account.key.<STORAGE>.dfs.core.windows.net: <KEY>
     flink.hadoop.fs.azure.account.key.<STORAGE>.dfs.core.windows.net: <KEY>
     

• Here's an overview of hive-dialect queries

  • Executing Hive dialect in Flink without partitioning

    root [ ~ ]# ./bin/sql-client.sh
    Flink SQL>
    Flink SQL> create catalog myhive with ('type' = 'hive', 'hive-conf-dir' = '/opt/hive-conf');
    [INFO] Execute statement succeed.
  
    Flink SQL> use catalog myhive;
    [INFO] Execute statement succeed.
  
    Flink SQL> load module hive;
    [INFO] Execute statement succeed.
  
    Flink SQL> use modules hive,core;
    [INFO] Execute statement succeed.
  
    Flink SQL> set table.sql-dialect=hive;
    [INFO] Session property has been set.
  
    Flink SQL> set sql-client.execution.result-mode=tableau;
    [INFO] Session property has been set.
  
    Flink SQL> select explode(array(1,2,3));Hive Session ID = 6ba45be2-360e-4bee-8842-2765c91581c8
  
  
  > [!WARNING]
  > An illegal reflective access operation has occurred
  
  > [!WARNING]
  > Illegal reflective access by org.apache.hadoop.hive.common.StringInternUtils (file:/opt/flink-webssh/lib/flink-sql-connector-hive-3.1.2_2.12-1.16-SNAPSHOT.jar) to field java.net.URI.string
  
  > [!WARNING]
  > Please consider reporting this to the maintainers of org.apache.hadoop.hive.common.StringInternUtils
  
  > [!WARNING]
  > `Use --illegal-access=warn` to enable warnings of further illegal reflective access operations
  
  > [!WARNING]
  >  All illegal access operations will be denied in a future release
  select explode(array(1,2,3));
  
  
  +----+-------------+
  | op |         col |
  +----+-------------+
  | +I |           1 |
  | +I |           2 |
  | +I |           3 |
  +----+-------------+
  
  Received a total of 3 rows
  
  Flink SQL> create table tttestHive Session ID = fb8b652a-8dad-4781-8384-0694dc16e837
  
  [INFO] Execute statement succeed.
  
  Flink SQL> insert into table tttestHive Session ID = f239dc6f-4b58-49f9-ad02-4c73673737d8),(3,'c'),(4,'d');
  
  [INFO] Submitting SQL update statement to the cluster...
  [INFO] SQL update statement has been successfully submitted to the cluster:
  Job ID: d0542da4c4252f9494298666ff4e9f8e
  
  Flink SQL> set execution.runtime-mode=batch;
  [INFO] Session property has been set.
  
  Flink SQL> select * from tttestHive Session ID = 61b6eb3b-90a6-499c-aced-0598366c5b31
  
  +-----+-------+
  | key | value |
  +-----+-------+
  |   1 |     a |
  |   1 |     a |
  |   2 |     b |
  |   3 |     c |
  |   3 |     c |
  |   3 |     c |
  |   4 |     d |
  |   5 |     e |
  +-----+-------+
  8 rows in set
  
  Flink SQL> QUIT;Hive Session ID = 2dadad92-436e-426e-a88c-66eafd740d98
  
  [INFO] Exiting Flink SQL CLI Client...
  
  Shutting down the session...
  done.
  root [ ~ ]# exit
  

  The data is written in the same container configured in the hive/warehouse directory.

  

  • Executing Hive dialect in Flink with partitions

  create table tblpart2 (key int, value string) PARTITIONED by ( part string ) tblproperties ('sink.partition-commit.delay'='1 s', 'sink.partition-commit.policy.kind'='metastore,success-file');

  insert into table tblpart2 Hive Session ID = 78fae85f-a451-4110-bea6-4aa1c172e282),(2,'b','d'),(3,'c','d'),(3,'c','a'),(4,'d','e');

Reference

• Hive Dialect in Apache Flink
• Apache, Apache Flink, Flink, and associated open source project names are trademarks of the Apache Software Foundation (ASF).