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https://issues.apache.org/jira/browse/HBASE-12751?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14642275#comment-14642275
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Elliott Clark commented on HBASE-12751:
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bq.Would it be better if mvcc didn't know anything about memstore? Should we be
asking mvcc to advance memstore...
Yeah that's pretty bad wording. Something like advanceReadPoint? Some other
wording for sure.
bq.We dropped an optimization when we let go of the below and instead just say
true for getRowLock.. Or was it something that just didn't work? (Or looks like
the semantic changed from waitFor to whether a read or write lock?)
The hope is that since we won't be blocking for any normal puts there is no
need for the added complexity.
> Allow RowLock to be reader writer
> ---------------------------------
>
> Key: HBASE-12751
> URL: https://issues.apache.org/jira/browse/HBASE-12751
> Project: HBase
> Issue Type: Bug
> Components: regionserver
> Affects Versions: 2.0.0, 1.3.0
> Reporter: Elliott Clark
> Assignee: Elliott Clark
> Fix For: 2.0.0, 1.3.0
>
> Attachments: HBASE-12751-v1.patch, HBASE-12751-v10.patch,
> HBASE-12751-v10.patch, HBASE-12751-v11.patch, HBASE-12751-v12.patch,
> HBASE-12751-v13.patch, HBASE-12751-v14.patch, HBASE-12751-v15.patch,
> HBASE-12751-v16.patch, HBASE-12751-v17.patch, HBASE-12751-v2.patch,
> HBASE-12751-v3.patch, HBASE-12751-v4.patch, HBASE-12751-v5.patch,
> HBASE-12751-v6.patch, HBASE-12751-v7.patch, HBASE-12751-v8.patch,
> HBASE-12751-v9.patch, HBASE-12751.patch
>
>
> Right now every write operation grabs a row lock. This is to prevent values
> from changing during a read modify write operation (increment or check and
> put). However it limits parallelism in several different scenarios.
> If there are several puts to the same row but different columns or stores
> then this is very limiting.
> If there are puts to the same column then mvcc number should ensure a
> consistent ordering. So locking is not needed.
> However locking for check and put or increment is still needed.
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