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From "Ashish Thusoo (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HIVE-65) Implict conversion from integer to long broken for Dynamic Serde tables
Date Mon, 01 Dec 2008 22:56:44 GMT

    [ https://issues.apache.org/jira/browse/HIVE-65?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12652192#action_12652192
] 

Ashish Thusoo commented on HIVE-65:
-----------------------------------

Actually mysql supports implicit conversions in both directions and that is what got me thinking
that perhaps we should also be supporting both.

http://dev.mysql.com/doc/refman/5.0/en/type-conversion.html

If we go the polymorphism route we would have to be very careful while adding UDFs. The UDF
writers will have to really understand how for implicit conversion they have to implement
functions with different signatures and that would just make it that much harder for them
to write UDFs that can take advantage of implicit conversion. In fact polymorphism in the
comparison function is the reason why we are hitting this problem in the
first place. 


The problem with going both ways is truly the one that caused us a lot of pain initially.
However, that does not get solved by restricting the conversion possibilities. If for example
we have a udf that takes two forms:

a) evaluate(string, string, int)
b) evaluate(int, string, string)

then even if we only allow string to be converted to int and not vice versa we have an ambiguous
match for

evaluate(1, 'abc', 2)

and we would not know which one to pick. This is what I mean by polymorphism causing these
issues. The comparison functions are
polymorphic and they are the ones that lead to the problem of ambiguity.


> Implict conversion from integer to long broken for Dynamic Serde tables
> -----------------------------------------------------------------------
>
>                 Key: HIVE-65
>                 URL: https://issues.apache.org/jira/browse/HIVE-65
>             Project: Hadoop Hive
>          Issue Type: Bug
>          Components: Query Processor
>            Reporter: Ashish Thusoo
>            Assignee: Zheng Shao
>
> For a dynamic serde table that has a bigint column, implict conversion from int to bigint
seems to be broken. I have not verified this for other tables.

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