[jira] Commented: (HIVE-790) race condition related to ScriptOperator + UnionOperator

[Ning Zhang (JIRA)]

    [ 
https://issues.apache.org/jira/browse/HIVE-790?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12747574#action_12747574
 ] 

Ning Zhang commented on HIVE-790:
---------------------------------

The above query still has semantics analysis error. Here's a working example 
demonstrating the bug:

select * from (
    select transform(a) using 'cat' as cola from nzhang_tt 
  union all 
    select transform(a) using 'cat' as cola from nzhang_tt) s;


The result is 3 rows:
1
2
3

But the query:

select cola from (
    select a as cola from nzhang_tt 
  union all 
    select a as cola from nzhang_tt) s;

returns 6 rows:

1
1
2
2
3
3



> race condition related to ScriptOperator + UnionOperator
> --------------------------------------------------------
>
>                 Key: HIVE-790
>                 URL: https://issues.apache.org/jira/browse/HIVE-790
>             Project: Hadoop Hive
>          Issue Type: Bug
>            Reporter: Zheng Shao
>            Assignee: Ning Zhang
>
> ScriptOperator uses a second thread to output the rows to the children 
> operators. In a corner case which contains a union, 2 threads might be 
> outputting data into the same operator hierarchy and caused race conditions.
> {code}
> CREATE TABLE tablea (cola STRING);
> SELECT *
> FROM (
>     SELECT TRANSFORM(cola)
>     USING 'cat'
>     AS cola
>     FROM tablea
>   UNION ALL
>     SELECT cola as cola
>     FROM tablea
> ) a;
> {code}

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