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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-13497) Remove MVCC stamps from HFile when that is safe
Date Thu, 30 Apr 2015 16:41:07 GMT

    [ https://issues.apache.org/jira/browse/HBASE-13497?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14521788#comment-14521788
] 

Lars Hofhansl commented on HBASE-13497:
---------------------------------------

Arrgghh... Lemme commit this today. Talked with [~stack] offline. As long as we zero the MVCC
stamps, this is safe (just avoids storing stamps that are know to be zero).
In another issue we need to discuss when exactly it _is_ safe to zero the MVCC stamps.

> Remove MVCC stamps from HFile when that is safe
> -----------------------------------------------
>
>                 Key: HBASE-13497
>                 URL: https://issues.apache.org/jira/browse/HBASE-13497
>             Project: HBase
>          Issue Type: Sub-task
>          Components: Scanners
>            Reporter: Lars Hofhansl
>            Assignee: Lars Hofhansl
>              Labels: performance
>             Fix For: 2.0.0, 1.0.2, 1.2.0, 1.1.1
>
>         Attachments: 13497.txt
>
>
> See discussion in HBASE-13389.
> The optimization was initially put in with HBASE-8166, HBASE-12600 undoes it, this will
partially restores it.
> Instead of checking the MVCC readpoints against the oldest current scanner, we check
that all are 0, if so, we do not need to write them.



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