[jira] [Assigned] (HIVE-25159) Remove support for ordered results in llap external client library

["Shubham Chaurasia (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HIVE-25159?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Shubham Chaurasia reassigned HIVE-25159:
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> Remove support for ordered results in llap external client library
> ------------------------------------------------------------------
>
>                 Key: HIVE-25159
>                 URL: https://issues.apache.org/jira/browse/HIVE-25159
>             Project: Hive
>          Issue Type: Bug
>          Components: Clients, Hive
>            Reporter: Shubham Chaurasia
>            Assignee: Shubham Chaurasia
>            Priority: Major
>
> Currently when querying via llap external client framework, in case of order by queries -
> 1. Due to the fact that spark-llap used to wrap actual query in a subquery as mentioned in [HIVE-19794|https://issues.apache.org/jira/browse/HIVE-19794]
> a) We had to detect order by like - 
> {code}
> orderByQuery = plan.getQueryProperties().hasOrderBy() || plan.getQueryProperties().hasOuterOrderBy();
> {code}
> Due to this we recently saw an exception like below for one of the queries that did not have an outer order by (It was having an order by in a subquery)
> {code}
> org.apache.hive.service.cli.HiveSQLException: java.io.IOException: org.apache.hadoop.hive.ql.metadata.HiveException: java.io.IOException:
> java.lang.IllegalStateException: Requested to generate single split. Paths and fileStatuses are expected to be 1. Got paths: 1 fileStatuses: 7
> {code}
> b) Also we had to disable following optimization - 
> {code}
> HiveConf.setBoolVar(conf, ConfVars.HIVE_REMOVE_ORDERBY_IN_SUBQUERY, false);
> {code}
> 2. By default we have {{hive.llap.external.splits.order.by.force.single.split=true}} which forces us to generate single split leading to performance bottleneck. 
> We should remove ordering support altogether from llap external client repo and let clients handle it at their end.



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