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https://issues.apache.org/jira/browse/CASSANDRA-9988?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16102358#comment-16102358
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Benedict commented on CASSANDRA-9988:
-------------------------------------
So, I took a quick peek at your actual test cases, and it seems you're only
ever seeking into an iterator the once with a uniform key across its domain,
then discarding it. In this scenario, yes, you would expect exponential search
to be more costly.
However, these are iterators, and the expectation is that there will be
multiple seeks during the iterator's lifetime. I had assumed that your
searchFound and searchNotFound enumerated (searched for) a sequence of found /
not found keys. There should probably be such variants.
All that said, I feel like this ticket has dragged on long enough and we're
probably well past diminishing returns for the change itself. But these
benchmarks are likely to persist a lot better than this discussion, so it is
probably worthwhile getting them right. It's also the case that we already use
exponential search for the branch iterator (though this was decided back on 2.2
storage format, so our N was much larger), and we should probably be consistent
and settle it once and for all.
> Introduce leaf-only iterator
> ----------------------------
>
> Key: CASSANDRA-9988
> URL: https://issues.apache.org/jira/browse/CASSANDRA-9988
> Project: Cassandra
> Issue Type: Sub-task
> Reporter: Benedict
> Assignee: Jay Zhuang
> Priority: Minor
> Labels: patch
> Fix For: 4.0
>
> Attachments: 9988-data.png, 9988-result2.png, 9988-result3.png,
> 9988-result.png, 9988-test-result3.png, 9988-trunk-new.txt,
> 9988-trunk-new-update.txt, trunk-9988.txt
>
>
> In many cases we have small btrees, small enough to fit in a single leaf
> page. In this case it _may_ be more efficient to specialise our iterator.
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