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From "Julien Le Dem (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (PIG-2815) class loader management in PigContext
Date Thu, 06 Dec 2012 22:11:09 GMT

    [ https://issues.apache.org/jira/browse/PIG-2815?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13525809#comment-13525809
] 

Julien Le Dem commented on PIG-2815:
------------------------------------

0.11/trunk sounds good to me

                
> class loader management in PigContext
> -------------------------------------
>
>                 Key: PIG-2815
>                 URL: https://issues.apache.org/jira/browse/PIG-2815
>             Project: Pig
>          Issue Type: Bug
>          Components: impl
>    Affects Versions: 0.9.0
>            Reporter: Raghu Angadi
>            Assignee: Raghu Angadi
>             Fix For: 0.11
>
>         Attachments: PIG-2815-branch-0.9.patch, PIG-2815-branch-0.9.patch, PIG-2815.patch,
PIG-2815.patch
>
>
> The way {{PigContext.classloader}} and resolveClassName() are managed can lead to strange
class loading issues, especially when not all {{register}} statements are at the top (example
in the first comment).
> Two factors contribute to this: sometimes only one of them and sometimes together:
>  # a new classloader (CL) is created after registering each jar.
>     ** but the new jar's parent is the root CL rather than previous CL, effectively throwing
previous CL away.
>  # resolveClassName() caches classes based on just the name
>     ** A class is not defined by name alone. Classes loaded by two different unrelated
CLs are different objects even if both extract the class from same physical jar file.
>     ** because of (1), the cached class is not necessarily same as the class that would
be loaded based on 'current' CL
> having different class objects for same class have many subtle side effects. e.g. there
would be two instances of static variables. 
> I think both should be fixed.. thought fixing one of them might be good enough in many
cases. I will add a patch.
>        

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