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From "Doug Cutting (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-3414) Facility to query serializable types such as Writables for 'raw length'
Date Tue, 20 May 2008 16:09:55 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3414?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12598343#action_12598343
] 

Doug Cutting commented on HADOOP-3414:
--------------------------------------

Perhaps we could add a SizedWritable sub-interface or abstract class, then change Text &
BytesWritable to extend that instead.  Then WritableSerializer#getSize(Writable) could use
instanceof to decide whether to call getSize() or simply return -1.  It's a little ugly to
use instanceof, but it would be back-compatible, I think.

What we really need is a benchmark that shows this provides some significant performance improvement.
 If it does, then it's probably worth finding the best compromise between back-compatiblity,
elegance and performance.

> Facility to query serializable types such as Writables for 'raw length'
> -----------------------------------------------------------------------
>
>                 Key: HADOOP-3414
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3414
>             Project: Hadoop Core
>          Issue Type: Improvement
>          Components: io
>            Reporter: Arun C Murthy
>
> Currently we need to jump through hoops to get the 'raw length' of serializable types
for e.g. SequenceFile.Writer.append needs to copy the key/value into a buffer and then check
the buffer's size to figure the record/key/value lenghts. Obviously this can be improved to
do away with the extra copy if we had types which could be queried for it's raw-length.
> Thoughts?

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