[
https://issues.apache.org/jira/browse/DRILL-6734?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16632277#comment-16632277
]
Hanumath Rao Maduri commented on DRILL-6734:
--------------------------------------------
[~appler] Can you please post the plan for this query.
Please use the following queries to get the plan.
{code:java}
explain plan including all attributes for select count(*) from
ngmysql.information_schema.`PROCESSLIST`{code}
and also with alias name.
{code:java}
explain plan including all attributes for select count(*) as num from
ngmysql.information_schema.`PROCESSLIST`{code}
> Unable to find value vector of path `EXPR$0`, returning null instance.
> ----------------------------------------------------------------------
>
> 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
> Priority: Major
>
> 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}
--
This message was sent by Atlassian JIRA
(v7.6.3#76005)
