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From "Hyunsik Choi (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (TAJO-215) Catalog should allow compatible types when finding functions
Date Wed, 02 Apr 2014 18:03:14 GMT

    [ https://issues.apache.org/jira/browse/TAJO-215?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13957960#comment-13957960
] 

Hyunsik Choi commented on TAJO-215:
-----------------------------------

Hi Alvin,

Thank you for your work! Your patch looks nice for me. You seem to get the point the issue
intended even though the description is very brief.

In addition, there are more compatible relationships by using upper casting. For example,
INT1 can be casted to INT2, INT4, INT8 in our Datum system. Also, FLOAT4 can be casted to
FLOAT8.

With these compatible relationships, we may use the following priority of function finding.


1) Find a exact matched function
2) Find a compatible function by using upper casting

For example, let us assume that there are two functions:
* {{INT4 func1(INT4)}}
* {{INT8 func1(INT8}}

When a function call {{func1(INT4)}} is issued,  the exact matched function {{func1(INT4)}}
will be retrieved. If there were no {{func1(INT4)}}, {{func1(INT8)}} will be retrieved.

If there are more than one compatible function, it would be great to retrieve a more close
compatible function. For example, there are {{func1(INT2)}}, {{func1(INT4)}}, and {{func1(INT8)}}.
When {{func1(INT2)}} is issued, it would be better to retrieve {{func1(INT4)}} instead of
{{func1(INT8)}} for more computation efficiency.

If you have any suggestion, feel free suggest anything.

Best regards,
Hyunsik

> Catalog should allow compatible types when finding functions
> ------------------------------------------------------------
>
>                 Key: TAJO-215
>                 URL: https://issues.apache.org/jira/browse/TAJO-215
>             Project: Tajo
>          Issue Type: Sub-task
>          Components: catalog, function/udf
>    Affects Versions: 0.8-incubating, 1.0-incubating
>            Reporter: Hyunsik Choi
>            Assignee: Alvin Henrick
>            Priority: Critical
>              Labels: patch
>             Fix For: 0.8-incubating, 1.0-incubating
>
>         Attachments: TAJO-215.Henrick.01.patch.txt
>
>
> Current catalog is strong typed. Given a find request, it only can search for a certain
function with the same argument types. However, in many cases, catalog should find functions
with compatible parameter types.



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