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From "Stu Hood (JIRA)" <j...@apache.org>
Subject [jira] Commented: (CASSANDRA-2062) Use more efficient merge algorithm
Date Thu, 27 Jan 2011 09:27:44 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-2062?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12987452#action_12987452
] 

Stu Hood commented on CASSANDRA-2062:
-------------------------------------

The times in that paste aren't supposed to be significant... I was just trying to get the
count of comparisons, so I was doing other things with my laptop. That test uses very small
keys (<6 bytes), so the comparisons are relatively cheap. 

> Use more efficient merge algorithm
> ----------------------------------
>
>                 Key: CASSANDRA-2062
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-2062
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Stu Hood
>            Priority: Minor
>             Fix For: 0.7.2
>
>         Attachments: 0001-Improved-iterator-for-merging-sorted-iterators.txt, 0002-Quickie-instrumentation-for-comparisons.txt,
0003-Replace-Collating-with-Merge-in-CompactionIterator.txt, 0004-Port-LazilyCompactedRow-ReducingKeyIterator-RangeSlice.txt,
0005-Remove-temporary-instrumentation-and-CollatingIterator.txt
>
>
> For {{M}} iterators containing {{N}} total items, commons.collections.CollatingIterator
performs a {{O(M*N)}} merge, and calls hasNext multiple times per returned value. We can do
better.

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