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From "Jeffrey Zhong (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-11315) Keeping MVCC for configurable longer time
Date Wed, 02 Jul 2014 17:47:26 GMT

    [ https://issues.apache.org/jira/browse/HBASE-11315?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14050474#comment-14050474
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Jeffrey Zhong commented on HBASE-11315:
---------------------------------------

{quote}
Make it 7 days on commit?
{quote}
Currently major compaction is set to 7 days. So hfile creation timestamp is normally <=
7 days old. We may end up keep mvcc forever because we're using hfile creation time to determine
if to removing mvcc. I can set it to 6 days though upon commit. Thanks.


> Keeping MVCC for configurable longer time 
> ------------------------------------------
>
>                 Key: HBASE-11315
>                 URL: https://issues.apache.org/jira/browse/HBASE-11315
>             Project: HBase
>          Issue Type: Improvement
>    Affects Versions: 0.99.0
>            Reporter: Jeffrey Zhong
>            Assignee: Jeffrey Zhong
>         Attachments: hbase-11315.patch
>
>
> After hbase-8763, we need keep mvcc number longer in hfile so that it can be used to
order changes during writes. For example, the known put,delete,put,... scenario, cross region
server scan, out of order puts(in recovery case).
> Current thinking is that we make the retention period configurable(below we're using
1 day to explain). During major compaction, we check hfile's creation time if a hfile creation
time is older than 1 day then all mvcc of KVs in that hfile will be removed. If a hfile is
created within 1 day, then all mvccs of KVs in that hfile will be kept. 
> In case there are time clock skew, we can firstly sort hfiles based on its seqId in ascending
order and find the first hfile's creation time stamp less than 1 day. Then mvcc of all hfiles
before the found file will be removed during compaction. 



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