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https://issues.apache.org/jira/browse/PIG-2815?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13525809#comment-13525809
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Julien Le Dem commented on PIG-2815:
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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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