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From "Liang Xie (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-7845) optimize hfile index key
Date Fri, 22 Mar 2013 03:11:15 GMT

    [ https://issues.apache.org/jira/browse/HBASE-7845?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13609849#comment-13609849
] 

Liang Xie commented on HBASE-7845:
----------------------------------

Hi [~stack], the expected blocks read number being reduced because:
Without patch, the search for row/cf1/col5 is done by looking for "row/cf1/col5/LATEST_TIMESTAMP/...",
and this will land us in previous block(col4), found mis-matched(blockseek return 1), then
advance to current block(issued a HFileScanner.next operation).

With patch, due to faked index key effect, we locate the current block(col5) directly and
blockSeek return -2, then we don't need to request HFileScanner.next, which will call readNextDataBlock
internally

Hope it's clear, sorry for my poor english:)
                
> optimize hfile index key
> ------------------------
>
>                 Key: HBASE-7845
>                 URL: https://issues.apache.org/jira/browse/HBASE-7845
>             Project: HBase
>          Issue Type: Improvement
>          Components: HFile
>    Affects Versions: 0.96.0
>            Reporter: Liang Xie
>            Assignee: Liang Xie
>             Fix For: 0.98.0
>
>         Attachments: HBASE-7845.txt, HBASE-7845-v2.txt, HBASE-7845-v3.txt, HBASE-7845-v4.txt,
HBASE-7845-v5.txt, HBASE-7845-v6.txt, HBASE-7845-v7.txt, HBASE-7845-v8.txt
>
>
> Leveldb uses ByteWiseComparatorImpl::FindShortestSeparator() & FindShortSuccessor()
to reduce index key size, it would be helpful under special conditions.

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