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Date: Fri, 25 Nov 2016 14:44:58 +0000 (UTC)
From: "Duo Zhang (JIRA)" <jira@apache.org>
To: issues@hbase.apache.org
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Subject: [jira] [Commented] (HBASE-17167) Pass mvcc to client when scan
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archived-at: Fri, 25 Nov 2016 14:45:00 -0000


    [ https://issues.apache.org/jira/browse/HBASE-17167?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15696014#comment-15696014 ] 

Duo Zhang commented on HBASE-17167:
-----------------------------------

And there is still a problem that we may read inconsistent data when restart a scanner. When compaction, we will get a smallestReadPoint. For all cells whose mvcc is greater than this value, we will never remove it, and not use it to delete any other values if it is a delete marker either. If a region is moved and start a compaction before we restart the scanner, we may have a smallestReadPoint which is greater than the mvcc of our scanner, if there is a delete marker in the range between the smallestReadPoint and the mvcc of our scanner, then we may lose some cells which should be returned to us.

I think this could be addressed in another issue(Yes yes, I do not good way to fix it right now!).

Thanks.

> Pass mvcc to client when scan
> -----------------------------
>
>                 Key: HBASE-17167
>                 URL: https://issues.apache.org/jira/browse/HBASE-17167
>             Project: HBase
>          Issue Type: Sub-task
>          Components: Client, scan
>            Reporter: Duo Zhang
>            Assignee: Duo Zhang
>             Fix For: 2.0.0, 1.4.0
>
>         Attachments: HBASE-17167.patch
>
>
> For the current implementation, if we use batch or allowPartial when scan, then the row level atomic can not be guaranteed if we need to restart a scan in the middle of a record due to region move or something else.
> We can return the mvcc used to open scanner to client and client could use this mvcc to restart a scan to get row level atomic.


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