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From "Szehon Ho (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-8448) Union All might not work due to the type conversion issue
Date Wed, 15 Oct 2014 17:38:34 GMT

    [ https://issues.apache.org/jira/browse/HIVE-8448?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14172650#comment-14172650
] 

Szehon Ho commented on HIVE-8448:
---------------------------------

This looks fine to me.  Only style feedback is please follow the common style convention in
GenericUDFUtils, like put parenthesis for if {...} else {...}, and also put a space after
if.  And the method name capitalization should be updatePriv, although I would suggest renaming
it to avoid confusion (when I first read it, I thought its updating the privilege).

To be honest I'm not the expert of union, I wonder if [~jdere], [~navis] would have any further
comment?  If not, +1 after these changes, pending the test.

> Union All might not work due to the type conversion issue
> ---------------------------------------------------------
>
>                 Key: HIVE-8448
>                 URL: https://issues.apache.org/jira/browse/HIVE-8448
>             Project: Hive
>          Issue Type: Bug
>    Affects Versions: 0.13.1
>            Reporter: Chaoyu Tang
>            Assignee: Yongzhi Chen
>            Priority: Minor
>         Attachments: HIVE-8448.1.patch
>
>
> create table t1 (val date);
> insert overwrite table t1 select '2014-10-10' from src limit 1;
> create table t2 (val varchar(10));
> insert overwrite table t2 select '2014-10-10' from src limit 1; 
> ==
> Query:
> select t.val from
> (select val from t1
> union all
> select val from t1
> union all
> select val from t2
> union all
> select val from t1) t;
> ==
> Will throw exception: 
> {code}
> Caused by: org.apache.hadoop.hive.ql.metadata.HiveException: Incompatible types for union
operator
> 	at org.apache.hadoop.hive.ql.exec.UnionOperator.initializeOp(UnionOperator.java:86)
> 	at org.apache.hadoop.hive.ql.exec.Operator.initialize(Operator.java:380)
> 	at org.apache.hadoop.hive.ql.exec.Operator.initialize(Operator.java:464)
> 	at org.apache.hadoop.hive.ql.exec.Operator.initializeChildren(Operator.java:420)
> 	at org.apache.hadoop.hive.ql.exec.SelectOperator.initializeOp(SelectOperator.java:65)
> 	at org.apache.hadoop.hive.ql.exec.Operator.initialize(Operator.java:380)
> 	at org.apache.hadoop.hive.ql.exec.Operator.initialize(Operator.java:464)
> 	at org.apache.hadoop.hive.ql.exec.Operator.initializeChildren(Operator.java:420)
> 	at org.apache.hadoop.hive.ql.exec.TableScanOperator.initializeOp(TableScanOperator.java:193)
> 	at org.apache.hadoop.hive.ql.exec.Operator.initialize(Operator.java:380)
> 	at org.apache.hadoop.hive.ql.exec.MapOperator.initializeOp(MapOperator.java:443)
> 	at org.apache.hadoop.hive.ql.exec.Operator.initialize(Operator.java:380)
> 	at org.apache.hadoop.hive.ql.exec.mr.ExecMapper.configure(ExecMapper.java:133)
> 	... 22 more
> {code}
> It was because at this query parse step, getCommonClassForUnionAll is used, but at execution
getCommonClass is used. They are not used consistently in union. The later one does not support
the implicit conversion from date to string, which is the problem cause.
> The change might be simple to fix this particular union issue but I noticed that there
are three versions of getCommonClass: getCommonClass, getCommonClassForComparison, getCommonClassForUnionAll,
and wonder if they need to be cleaned and refactored.



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