[jira] [Created] (HIVE-17532) Hive on Spark query compilation starts Spark session

["Peter Csaszar (JIRA)" <ji...@apache.org>]

Peter Csaszar created HIVE-17532:
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             Summary: Hive on Spark query compilation starts Spark session
                 Key: HIVE-17532
                 URL: https://issues.apache.org/jira/browse/HIVE-17532
             Project: Hive
          Issue Type: Bug
          Components: HiveServer2
    Affects Versions: 2.2.0
            Reporter: Peter Csaszar
            Priority: Minor


Hive on Spark query compilation starts a new Spark session when some kind of aggregation is present:

0: jdbc:hive2://localhost:10000/default> set hive.execution.engine=spark;
No rows affected (0.013 seconds)
0: jdbc:hive2://localhost:10000/default> explain select distinct label0 from iris;
INFO  : Compiling command(queryId=hive_20170912151212_914ee322-28dd-442a-9dd9-7ed00a6a8caf): explain select distinct label0 from iris
INFO  : Semantic Analysis Completed
INFO  : Returning Hive schema: Schema(fieldSchemas:[FieldSchema(name:Explain, type:string, comment:null)], properties:null)
INFO  : Completed compiling command(queryId=hive_20170912151212_914ee322-28dd-442a-9dd9-7ed00a6a8caf); Time taken: *40.594* seconds

Spark job started, all consecutive explain statements are fast:

0: jdbc:hive2://localhost:10000/default> explain select distinct a1 from iris;
INFO  : Compiling command(queryId=hive_20170912151414_faacda24-290e-48bb-9daf-3f301fc170c1): explain select distinct label0 from iris
INFO  : Semantic Analysis Completed
INFO  : Returning Hive schema: Schema(fieldSchemas:[FieldSchema(name:Explain, type:string, comment:null)], properties:null)
INFO  : Completed compiling command(queryId=hive_20170912151414_faacda24-290e-48bb-9daf-3f301fc170c1); Time taken: *0.275* seconds

Killing the Spark job, the same query is still fast, and no new Spark job has been started:

0: jdbc:hive2://localhost:10000/default> explain select distinct a2 from iris;
INFO  : Compiling command(queryId=hive_20170912151616_a7ea83b6-03ce-4636-b3d4-be6feadcde35): explain select distinct label0 from iris
INFO  : Semantic Analysis Completed
INFO  : Returning Hive schema: Schema(fieldSchemas:[FieldSchema(name:Explain, type:string, comment:null)], properties:null)
INFO  : Completed compiling command(queryId=hive_20170912151616_a7ea83b6-03ce-4636-b3d4-be6feadcde35); Time taken: *0.213* seconds

The code in question:
SetSparkReducerParallelism.java:
sparkSessionManager = SparkSessionManagerImpl.getInstance();
sparkSession = SparkUtilities.getSparkSession(context.getConf(), sparkSessionManager);
sparkMemoryAndCores = sparkSession.getMemoryAndCores();

The created Spark session is used for getting the number of cores and memory only. This could be determined from the configurations, without actually starting a session.



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