[jira] [Updated] (HIVE-8312) Implicit type conversion on Join keys

["Lin Liu (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HIVE-8312?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Lin Liu updated HIVE-8312:
--------------------------
    Description: 
Suppose we have a query as follows.
"
SELECT ....
FROM A LEFT SEMI JOIN B
ON (A.col1 = B.col2)
WHERE ...
"
If A.col1 is of STRING type, but B.col2 is of BIGINT, or DOUBLE,
Hive finds the common compatible type (here is DOUBLE) for both cols and do implicit type conversion.

However, this implicit conversion from STRING to DOUBLE could produce NULL values, which could further
generate unexpected results, like skew.

I just wonder: Is this case by design? If so, what is the logic? If not, how can we solve it?

> Implicit type conversion on Join keys
> -------------------------------------
>
>                 Key: HIVE-8312
>                 URL: https://issues.apache.org/jira/browse/HIVE-8312
>             Project: Hive
>          Issue Type: Bug
>          Components: Query Processor
>            Reporter: Lin Liu
>
> Suppose we have a query as follows.
> "
> SELECT ....
> FROM A LEFT SEMI JOIN B
> ON (A.col1 = B.col2)
> WHERE ...
> "
> If A.col1 is of STRING type, but B.col2 is of BIGINT, or DOUBLE,
> Hive finds the common compatible type (here is DOUBLE) for both cols and do implicit type conversion.
> However, this implicit conversion from STRING to DOUBLE could produce NULL values, which could further
> generate unexpected results, like skew.
> I just wonder: Is this case by design? If so, what is the logic? If not, how can we solve it?



--
This message was sent by Atlassian JIRA
(v6.3.4#6332)