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From "Ajay Garg (JIRA)" <j...@apache.org>
Subject [jira] Updated: (PIG-255) Calling non default constructor of Final class from Main class in UDF
Date Tue, 17 Jun 2008 09:27:45 GMT

     [ https://issues.apache.org/jira/browse/PIG-255?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Ajay Garg updated PIG-255:
--------------------------

    Attachment: cons.patch
                test.patch

Hi,
     I am attaching two patch to explain and resolve this issue . First is test.patch which
create TestUDF.java and modify build.xml to run this test case. run "ant udftest" to run this
test case. In this test case I return Final.class.getName() + "(" schema name + ")" in getFinal()
method. Calling final class with arguments should be right way doing but it gives following
error. 
  java.lang.ClassNotFoundException: Could not resolve org.apache.pig.test.TestUDF$Test$Final('a')
using imports: [, org.apache.pig.builtin., com.yahoo.pig.yst.sds.ULT., org.apache.pig.impl.builtin.]

The reason for this problem is that resolveClassName method doesn't think of its args as specs
and assumes them to be just names. So in createJar, when the func spec TestUDF$Test$Final(a')
is being resolved it fails.

The second patch cons.patch resolve this problem. It finds class name in resovleClassName
by searching for index of "(" which I think should be the correct way of resolving this .
Please give your feedbacks .
Thanks

> 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
>         Attachments: cons.patch, test.patch
>
>
> 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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