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From "Andrew Purtell (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-13109) Make better SEEK vs SKIP decisions during scanning
Date Tue, 17 Mar 2015 01:11:39 GMT

    [ https://issues.apache.org/jira/browse/HBASE-13109?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14364356#comment-14364356
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Andrew Purtell commented on HBASE-13109:
----------------------------------------

I've confirmed 0.98.12 snapshots are available in Apache Maven now.

Be sure the Apache snapshots repository is included in your POM:
{noformat}
    <repository>
      <id>apache.snapshots</id>
      <url>http://repository.apache.org/snapshots/</url>
      <snapshots>
        <enabled>true</enabled>
      </snapshots>
    </repository>
{noformat}

Use the versions "0.98.12-hadoop2-SNAPSHOT" for the Hadoop 2 build, "0.98.12-hadoop1-SNAPSHOT"
for the Hadoop 1 build.

> Make better SEEK vs SKIP decisions during scanning
> --------------------------------------------------
>
>                 Key: HBASE-13109
>                 URL: https://issues.apache.org/jira/browse/HBASE-13109
>             Project: HBase
>          Issue Type: Improvement
>            Reporter: Lars Hofhansl
>            Assignee: Lars Hofhansl
>             Fix For: 2.0.0, 1.0.1, 1.1.0, 0.98.12
>
>         Attachments: 13109-0.98-v4.txt, 13109-trunk-v2.txt, 13109-trunk-v3.txt, 13109-trunk-v4.txt,
13109-trunk-v5.txt, 13109-trunk.txt, nextIndexKVChange_new.patch
>
>
> I'm re-purposing this issue to add a heuristic as to when to SEEK and when to SKIP Cells.
This has come up in various issues, and I think I have a way to finally fix this now. HBASE-9778,
HBASE-12311, and friends are related.
> --- Old description ---
> This is a continuation of HBASE-9778.
> We've seen a scenario of a very slow scan over a region using a timerange that happens
to fall after the ts of any Cell in the region.
> Turns out we spend a lot of time seeking.
> Tested with a 5 column table, and the scan is 5x faster when the timerange falls before
all Cells' ts.
> We can use the lookahead hint introduced in HBASE-9778 to do opportunistic SKIPing before
we actually seek.



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