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https://issues.apache.org/jira/browse/ACCUMULO-4468?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15511418#comment-15511418
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Keith Turner commented on ACCUMULO-4468:
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[~wmurnane] I like the change.  I wrote the comment and made the changes in Key 
that you referenced.  I remember doing the performance testing for that.  When 
I first experimented with the change, I tried comparing the byte arrays in 
reveres order.  That was much slower than comparing forward. So I avoiding that 
and found another strategy that worked well.  I think the concept is sound, but 
the performance testing is definitely needed to make sure it works as intended.

I also like the switch statement fall through, I think its slick.  If it 
doesn't exists, It would be nice to add a unit test that checks for correctness 
for keys that only differ by one field.  Basically ensure that each of the key 
field comparisons is tested.

> accumulo.core.data.Key.equals(Key, PartialKey) improvement
> ----------------------------------------------------------
>
>                 Key: ACCUMULO-4468
>                 URL: https://issues.apache.org/jira/browse/ACCUMULO-4468
>             Project: Accumulo
>          Issue Type: Improvement
>          Components: core
>    Affects Versions: 1.8.0
>            Reporter: Will Murnane
>            Priority: Trivial
>              Labels: newbie, performance
>         Attachments: benchmark.tar.gz, key_comparison.patch
>
>
> In the Key.equals(Key, PartialKey) overload, the current method compares 
> starting at the beginning of the key, and works its way toward the end. This 
> functions correctly, of course, but one of the typical uses of this method is 
> to compare adjacent rows to break them into larger chunks. For example, 
> accumulo.core.iterators.Combiner repeatedly calls this method with subsequent 
> pairs of keys.
> I have a patch which reverses the comparison order. That is, if the method is 
> called with ROW_COLFAM_COLQUAL_COLVIS, it will compare visibility, cq, cf, 
> and finally row. This (marginally) improves the speed of comparisons in the 
> relatively common case where only the last part is changing, with less 
> complex code.



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