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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