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https://issues.apache.org/jira/browse/ACCUMULO-4468?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15511398#comment-15511398
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Josh Elser commented on ACCUMULO-4468:
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Great stuff, [~wmurnane]! A few thoughts:

bq. the original equals() copied to the new class is called customVanilla, and 
the original equals() in the original Key class is called standardEquals. The 
numbers to compare are really the two custom* ones; the standardEquals value is 
given just to show that it's in the same ballpark. 

I'm not grok'ing the difference between customVanilla and standardEquals. Why 
the variance in these two? Shouldn't they be essentially equivalent?

bq. As a user of the API, I'd rather not have to think about equalsForward() 
versus equalsBackward().

I concur with you here.

bq. I agree that any change should start with prejudice against it. However, I 
think the numbers above prove my case: when keys are presented in sorted order, 
which happens often in Accumulo, the proposed method of comparing is slightly 
but noticeably faster. The degree of improvement depends on the data, but it 
doesn't perform worse than the current solution in any case that I tested.

Great, I hoped you didn't take my initial prejudice badly :). This is a great 
start. I'm curious trying to tweak a couple of other things. Sharing your 
project was super useful.

Ultimately, if these numbers are as they appear (better in some cases, no worse 
in others), this is a great improvement. Expecting large contiguous blocks of 
keys where row or row+cf change very infrequently makes sense to optimize. It 
appears that {{compareTo(Object}} is also using a separate code path, so I 
don't think this would have a big affect on things like creating RFiles for 
bulk imports. I need to search through usages though.

> 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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