Details
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Bug
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Status: Resolved
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Major
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Resolution: Fixed
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1.14.0
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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.
Description
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:
select count(*) from ngmysql.information_schema.`PROCESSLIST`
which returns
EXPR$0
-------------
<null>
and you could find this warning from the log:
Unable to find value vector of path `EXPR$0`, returning null instance.
But it works fine if you give an alias to the expression like this:
select count(*) as num from ngmysql.information_schema.`PROCESSLIST`;
which would end up giving this:
num ---------------------- 16
Here's the portion of logs regarding the sample query:
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
Attachments
Issue Links
- is related to
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DRILL-6893 Invalid output for star and self-join queries for RDBMS Storage Plugin
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- Resolved
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- links to