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Posted to issues@hbase.apache.org by "Lars Hofhansl (JIRA)" <ji...@apache.org> on 2015/04/30 18:41:07 UTC
[jira] [Commented] (HBASE-13497) Remove MVCC stamps from HFile when
that is safe
[ 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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