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

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

Shubham Chaurasia created HIVE-25159:
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             Summary: 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


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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