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From "Cheolgoo Kang (JIRA)" <j...@apache.org>
Subject [jira] [Created] (DRILL-6734) Unable to find
Date Fri, 07 Sep 2018 21:55:01 GMT
Cheolgoo Kang created DRILL-6734:
------------------------------------

             Summary: Unable to find 
                 Key: DRILL-6734
                 URL: https://issues.apache.org/jira/browse/DRILL-6734
             Project: Apache Drill
          Issue Type: Bug
          Components: Storage - JDBC
    Affects Versions: 1.14.0
         Environment: Apache Drill version 1.14.0 running on CentOS 7.0.1406.
MySQL version 5.5.43 running on CentOS 6.4.
MySQL connector/j version 5.1.44.
            Reporter: Cheolgoo Kang


Expressions in a query against JDBC without alias returns null as their value.

I was trying to run this sample query to retrieve count of a MySQL table connected to Drill
through the RDBMS storage plugin:
{code}
select count(*) from ngmysql.information_schema.`PROCESSLIST`
{code}
which returns
{code}
EXPR$0       
-------------
<null>       
{code}
and you could find this warning from the log:
{quote}
Unable to find value vector of path `EXPR$0`, returning null instance.
{quote}
But it works fine if you give an alias to the expression like this:
{code}
select count(*) as num from ngmysql.information_schema.`PROCESSLIST`;
{code}
which would end up giving this:
{code}
num                   
----------------------
16                    
{code}

Here's the portion of logs regarding the sample query:
{code}
2018-09-07 21:44:52,709 [246d0eaa-f8e6-9536-af0c-1df3932cce9f:foreman] INFO  o.a.drill.exec.work.foreman.Foreman
- Query text for query id 246d0eaa-f8e6-9536-af0c-1df3932cce9f: select count(*) from ngmysql.information_schema.`PROCESSLIST`
2018-09-07 21:44:52,752 [246d0eaa-f8e6-9536-af0c-1df3932cce9f:frag:0:0] INFO  o.a.d.e.w.fragment.FragmentExecutor
- 246d0eaa-f8e6-9536-af0c-1df3932cce9f:0:0: State change requested AWAITING_ALLOCATION -->
RUNNING
2018-09-07 21:44:52,753 [246d0eaa-f8e6-9536-af0c-1df3932cce9f:frag:0:0] INFO  o.a.d.e.w.f.FragmentStatusReporter
- 246d0eaa-f8e6-9536-af0c-1df3932cce9f:0:0: State to report: RUNNING
2018-09-07 21:44:52,756 [246d0eaa-f8e6-9536-af0c-1df3932cce9f:frag:0:0] WARN  o.a.d.e.e.ExpressionTreeMaterializer
- Unable to find value vector of path `EXPR$0`, returning null instance.
2018-09-07 21:44:52,759 [246d0eaa-f8e6-9536-af0c-1df3932cce9f:frag:0:0] INFO  o.a.d.e.w.fragment.FragmentExecutor
- 246d0eaa-f8e6-9536-af0c-1df3932cce9f:0:0: State change requested RUNNING --> FINISHED
2018-09-07 21:44:52,760 [246d0eaa-f8e6-9536-af0c-1df3932cce9f:frag:0:0] INFO  o.a.d.e.w.f.FragmentStatusReporter
- 246d0eaa-f8e6-9536-af0c-1df3932cce9f:0:0: State to report: FINISHED
{code}



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