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https://issues.apache.org/jira/browse/HBASE-17177?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15714147#comment-15714147
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ramkrishna.s.vasudevan commented on HBASE-17177:
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bq.If there is no requests within TTL milliseconds, we can remove the scanner.
So I think when we open a region, we can wait same time before we want to do a
major compaction. Although the scanner may has been expired at former RS, it is
safe and TTL is not a long time.
I think this is nice idea.
> Major compaction can break the region/row level atomic when scan even if we
> pass mvcc to client
> -----------------------------------------------------------------------------------------------
>
> Key: HBASE-17177
> URL: https://issues.apache.org/jira/browse/HBASE-17177
> Project: HBase
> Issue Type: Sub-task
> Components: scan
> Reporter: Duo Zhang
> Fix For: 2.0.0, 1.4.0
>
>
> We know that major compaction will actually delete the cells which are
> deleted by a delete marker. In order to give a consistent view for a scan, we
> need to use a map to track the read points for all scanners for a region, and
> the smallest one will be used for a compaction. For all delete markers whose
> mvcc is greater than this value, we will not use it to delete other cells.
> And the problem for a scan restart after region move is that, the new RS does
> not have the information of the scanners opened at the old RS before the
> client sends scan requests to the new RS which means the read points map is
> incomplete and the smallest read point maybe greater than the correct value.
> So if a major compaction happens at that time, it may delete some cells which
> should be kept.
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