[jira] [Created] (HIVE-8448) Union All might not work due to the type conversion issue

["Chaoyu Tang (JIRA)" <ji...@apache.org>]

Chaoyu Tang created HIVE-8448:
---------------------------------

             Summary: 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
            Reporter: Chaoyu Tang
            Priority: Minor


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 



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