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From Jeff Zhang <zjf...@gmail.com>
Subject Re: Input splits for sequence file input
Date Mon, 03 Dec 2012 02:08:03 GMT
method createRecordReader will handle the record boundary issue. You can
check the code for details

On Mon, Dec 3, 2012 at 6:03 AM, Jeff LI <uniquejeff@gmail.com> wrote:

> Hello,
>
> I was reading on the relationship between input splits and HDFS blocks and
> a question came up to me:
>
> If a logical record crosses HDFS block boundary, let's say block#1 and
> block#2, does the mapper assigned with this input split asks for (1) both
> blocks, or (2) block#1 and just the part of block#2 that this logical
> record extends to, or (3) block#1 and part of block#2 up to some sync point
> that covers this particular logical record?  Note the input is sequence
> file.
>
> I guess my question really is: does Hadoop operate on a block basis or
> does it respect some sort of logical structure within a block when it's
> trying to feed the mappers with input data.
>
> Cheers
>
> Jeff
>
>


-- 
Best Regards

Jeff Zhang

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