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https://issues.apache.org/jira/browse/HBASE-8763?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13857813#comment-13857813
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Jeffrey Zhong commented on HBASE-8763:
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I'm working with [~enis] on this though in a slow pace because the feature can
most likely be released in 0.99 or later. There are work left to be done like
upgrade handling & performance evaluation.
[~liyin] Not much special handing on log group commit which you can check on
hbase-8741. Basically log sequence number won't monotonically increase in a WAL
while it is for a single region. MVCC will become a region specific value not
global in RS level so we need to maintain a map region -> read point for
scanning.
> [BRAINSTORM] Combine MVCC and SeqId
> -----------------------------------
>
> Key: HBASE-8763
> URL: https://issues.apache.org/jira/browse/HBASE-8763
> Project: HBase
> Issue Type: Improvement
> Components: regionserver
> Reporter: Enis Soztutar
> Priority: Critical
> Attachments: hbase-8736-poc.patch, hbase-8763_wip1.patch
>
>
> HBASE-8701 and a lot of recent issues include good discussions about mvcc +
> seqId semantics. It seems that having mvcc and the seqId complicates the
> comparator semantics a lot in regards to flush + WAL replay + compactions +
> delete markers and out of order puts.
> Thinking more about it I don't think we need a MVCC write number which is
> different than the seqId. We can keep the MVCC semantics, read point and
> smallest read points intact, but combine mvcc write number and seqId. This
> will allow cleaner semantics + implementation + smaller data files.
> We can do some brainstorming for 0.98. We still have to verify that this
> would be semantically correct, it should be so by my current understanding.
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