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https://issues.apache.org/jira/browse/HADOOP-5589?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12701826#action_12701826
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Chris Douglas commented on HADOOP-5589:
---------------------------------------
Just a few minor nits:
* Instead of using {{BitSet::set(i, false)}}, {{BitSet::clear\(i)}} should
accomplish the same thing in {{TupleWritable::clearWritten}}; in the iterator,
using {{clear}} is probably more readable than {{flip}} though they're
obviously equivalent.
* The size check in {{equals}} can be dropped, since {{BitSet}} also performs
it in its {{equals}} implementation
* The loop in readBitSet would be easier to read as:
{code}
for (int offset = Long.SIZE; offset < nbits; offset += Byte.SIZE) {
{code}
* I'd replace {{setBit}} with the equivalent, single line of code in
{{writeBitSet}}
The rest of the changes look good.
> TupleWritable: Lift implicit limit on the number of values that can be stored
> -----------------------------------------------------------------------------
>
> Key: HADOOP-5589
> URL: https://issues.apache.org/jira/browse/HADOOP-5589
> Project: Hadoop Core
> Issue Type: Improvement
> Components: mapred
> Affects Versions: 0.19.1
> Reporter: Jingkei Ly
> Assignee: Jingkei Ly
> Attachments: HADOOP-5589-1.patch, HADOOP-5589-2.patch,
> HADOOP-5589-3.patch, HADOOP-5589-4.patch
>
>
> TupleWritable uses an instance field of the primitive type, long, which I
> presume is so that it can quickly determine if a position has been written to
> in its array of Writables (by using bit-shifting operations on the long
> field). The problem with this is that it implies that there is a maximum
> limit of 64 values you can store in a TupleWritable.
> An example of a use-case where I think this would be a problem is if you had
> two MR jobs with over 64 reduces tasks and you wanted to join the outputs
> with CompositeInputFormat - this will probably cause unexpected results in
> the current scheme.
> At the very least, the 64-value limit should be documented in TupleWritable.
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