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From "Thejas M Nair (JIRA)" <j...@apache.org>
Subject [jira] Created: (PIG-969) Default constructor of UDF gets called for UDF with parameterised constructor , if the udf has a getArgToFuncMapping function defined
Date Fri, 18 Sep 2009 23:46:16 GMT
Default constructor of UDF gets called for UDF with parameterised constructor , if the udf
has a getArgToFuncMapping function defined
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                 Key: PIG-969
                 URL: https://issues.apache.org/jira/browse/PIG-969
             Project: Pig
          Issue Type: Bug
          Components: impl
            Reporter: Thejas M Nair



This issue is discussed in  http://www.mail-archive.com/pig-user@hadoop.apache.org/msg00524.html
. I am able to reproduce the issue. While it is easy to fix the udf, it can take a lot of
time to figure out the problem (until they find this email conversation!).

The root cause is that when getArgToFuncMapping is defined in the udf , the FuncSpec returned
by the method replaces one set by define statement . The constructor arguments get lost. 
We can handle this in following ways -

1. Preserve the constructor arguments, and use it with the class name of the matching FuncSpec
from getArgToFuncMapping . 
2. Give an error if constructor paramerters are given for a udf which has FuncSpecs returned
from getArgToFuncMapping .

The problem with  approach 1 is that we are letting the user define the FuncSpec , so user
could have defined a FuncSpec with constructor (though they don't have a valid reason to do
so.). It is also possible the the constructor of the different class that matched might not
support same constructor parameters. The use of this function outside builtin udfs are also
probably not common.

With option 2, we are telling the user that this is not a supported use case, and user can
easily change the udf to fix the issue, or use the udf which would have matched given parameters
(which unlikely to have the getArgToFuncMapping method defined).

I am proposing that we go with option 2 . 


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