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From: Markus Jelsma <markus.jelsma@openindex.io>
Reply-To: markus.jelsma@openindex.io
Organization: Openindex
To: mapreduce-user@hadoop.apache.org
Subject: Re: Renaming WritableComparable and existing SequenceFiles
Date: Wed, 30 Nov 2011 17:18:38 +0100
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Solved!

Another tool reading the same files expects various childs of 
WritableComparable and Writable, this of course won't throw a class cast 
exception. That same tool writes the using the new class. In essence, i 
already had a converter tool.

Thanks

On Wednesday 30 November 2011 16:44:49 Markus Jelsma wrote:
> Hi,
> 
> I've built some SequenceFiles using a custom WritableComparable. I also
> decided to reorganize package structure and ended up renaming the whole
> thing. Since the key and value classes are embedded in the file i cannot
> read them because it either doesn't exist or cannot be cast in case the
> same classname lives in another package name.
> 
> I looked in the Job and SequenceFile and InputFormat API's but i cannot
> find something to tell the reader that the class is somewhere else now.
> Renaming using a hexeditor doesn't work as well because the package name's
> length is different now, leading to a lot of bad exceptions such as
> Unknown codec complaints.
> 
> I can still load the file by keeping the original WritableComparable and
> write back to disk using the new WritableComparable but that forces me to
> write some temporary code.
> 
> How can i tell the reader to use the new (but identical) class for
> WritableComparable when loading a SequenceFile? Or do i have to write some
> conversion code?
> 
> Thanks

-- 
Markus Jelsma - CTO - Openindex