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From "Olga Natkovich (JIRA)" <j...@apache.org>
Subject [jira] Commented: (PIG-255) Calling non default constructor of Final class from Main class in UDF
Date Fri, 06 Jun 2008 21:18:45 GMT

    [ https://issues.apache.org/jira/browse/PIG-255?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12603175#action_12603175
] 

Olga Natkovich commented on PIG-255:
------------------------------------

Hi Ajay,

I am trying to understand the issue that you are raising better. If I understand correctly,
you want to pass arguments to your UDF via define statement and you want the same arguments
to be used for all stages of algebraic function computation. Is this correct?

I looked at the code and it was not immediately obvious to me why it would not work right
now. We use the arguments in the constructor of the FuncEvalSpec so this data should be available
to all functions. What am I missing?

Also, a simple unit test that demonstrates the problem would be very helpful.

> Calling non default constructor of Final class from Main class in UDF
> ---------------------------------------------------------------------
>
>                 Key: PIG-255
>                 URL: https://issues.apache.org/jira/browse/PIG-255
>             Project: Pig
>          Issue Type: Improvement
>            Reporter: Ajay Garg
>            Priority: Minor
>
> Pig supports the use of define to call a non default constructor. Making it work across
Algebraic functions is not possible with the current code. The problem is once the func is
defined to use a non default constructor which takes in names of the variables, we have no
way of transmitting this information from the main class to the final class. We tried passing
the func spec through the call to getFinal(). That is, What ever names we get in the main
class we store it and when the getFinal method is called, instead of just passing the name
of the Final class we attach the string args received by the main class to the name to construct
a func spec. For ex. if define COV = Covariance('Population', 'Height'); Then we would have
the "Population' & 'Height' stored in the main class. A call to getFinal would return
Covariance$Final("Population", "Height") instead of just Covariance$Final. I guess this is
the right way to go. However, pig has a problem with this. The resolveClassName method doesn't
think of its args as specs and assumes them to be just names. So in createJar, when the func
spec, Covariance$Final("Population", "Height") is being resolved it fails. I think this is
an issue with pig and we need to resolve it by clipping the args before doing a resolveClassName.


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