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From "Jay Zhuang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-9988) Introduce leaf-only iterator
Date Sat, 29 Jul 2017 02:18:02 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-9988?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16105981#comment-16105981
] 

Jay Zhuang commented on CASSANDRA-9988:
---------------------------------------

Hi [~benedict], would you please point me the exponential search implementation for the branch
iterator?

I tried to improve the [expSearch|https://github.com/cooldoger/cassandra/commit/a23a3422a894acb72a47975da035bbf8da50fc4b],
here is [the improved version|https://github.com/cooldoger/cassandra/commit/7330646e553afd4b4b0011f6163bf9032f9cb605]
which will do 1 comparison if it finds the target at the first stage. But that's optimized
to find the target on {{2^i}} position, doesn't cover position 0. To cover position 0 (the
first element), I need to add more checks and code, it makes the code hard to understand.
And if we really do that, I could have the same optimization for binarySearch (manually check
the first 1 or 2 elements), which results in the similar improvement.

> 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-test-result-expsearch.xlsx, 9988-test-result-raw.png, 9988-test-result.xlsx,
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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