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From "James Taylor (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-13109) Make better SEEK vs SKIP decisions during scanning
Date Thu, 12 Mar 2015 18:00:48 GMT

    [ https://issues.apache.org/jira/browse/HBASE-13109?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14359085#comment-14359085
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James Taylor commented on HBASE-13109:
--------------------------------------

Want to make sure I understand the b/w compat implications. Does this mean that our current
4.3 and below releases will no longer work with 0.98.12 and above? And that 4.4 and above
will only work with 0.98.12 and above?

> 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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