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From "Jonathan Hsieh (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-9969) Improve KeyValueHeap using loser tree
Date Mon, 18 Nov 2013 16:55:23 GMT

    [ https://issues.apache.org/jira/browse/HBASE-9969?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13825471#comment-13825471
] 

Jonathan Hsieh commented on HBASE-9969:
---------------------------------------

bq. I have not found a scenario, *yet*, where this is slower. Seems generally safe to pull
into all branches.

Emphasis mine. 

I'm a bit concerned with such a fundamental change going in without a way of "going back"
in the case we find a slower case, especially in the stable branch.  Wouldn't it be prudent
if this were to make it into 0.94 make it an option?



> Improve KeyValueHeap using loser tree
> -------------------------------------
>
>                 Key: HBASE-9969
>                 URL: https://issues.apache.org/jira/browse/HBASE-9969
>             Project: HBase
>          Issue Type: Improvement
>          Components: Performance, regionserver
>            Reporter: Chao Shi
>            Assignee: Chao Shi
>             Fix For: 0.98.0, 0.96.1, 0.94.15
>
>         Attachments: 9969-0.94.txt, hbase-9969-v2.patch, hbase-9969-v3.patch, hbase-9969.patch,
hbase-9969.patch, kvheap-benchmark.png, kvheap-benchmark.txt
>
>
> LoserTree is the better data structure than binary heap. It saves half of the comparisons
on each next(), though the time complexity is on O(logN).
> Currently A scan or get will go through two KeyValueHeaps, one is merging KVs read from
multiple HFiles in a single store, the other is merging results from multiple stores. This
patch should improve the both cases whenever CPU is the bottleneck (e.g. scan with filter
over cached blocks, HBASE-9811).
> All of the optimization work is done in KeyValueHeap and does not change its public interfaces.
The new code looks more cleaner and simpler to understand.



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