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From "Sergey Shelukhin (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-10241) implement mvcc-consistent scanners (across recovery)
Date Mon, 06 Jan 2014 22:43:53 GMT

    [ https://issues.apache.org/jira/browse/HBASE-10241?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13863546#comment-13863546
] 

Sergey Shelukhin commented on HBASE-10241:
------------------------------------------

Subtask 2 is trivial; the reason it is not done is that it is being done elsewhere (see how
it's resolved as dup), so since it's not blocking us here and now it doesn't make sense to
do double work. I am not working on this jira right now (will get back to it hopefully and
there's a patch out in client subtask), but the plan was that I will do 1 and 3, and then
take 2 if the other JIRA that does 2 is not done by then. 
HBASE-8763 does not need to block this, it's probably bigger than this entire JIRA. If it's
done before this due to delays, good, if not, also good :)


> implement mvcc-consistent scanners (across recovery)
> ----------------------------------------------------
>
>                 Key: HBASE-10241
>                 URL: https://issues.apache.org/jira/browse/HBASE-10241
>             Project: HBase
>          Issue Type: New Feature
>          Components: HFile, regionserver, Scanners
>    Affects Versions: 0.99.0
>            Reporter: Sergey Shelukhin
>            Assignee: Sergey Shelukhin
>         Attachments: Consistent scanners.pdf
>
>
> Scanners currently use mvcc for consistency. However, mvcc is lost on server restart,
or even a region move. This JIRA is to enable the scanners to transfer mvcc (or seqId, or
some other number, see HBASE-8763) between servers. First, client scanner needs to get and
store the readpoint. Second, mvcc needs to be preserved in WAL. Third, the mvcc needs to be
stored in store files per KV and discarded when not needed.



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