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From "Dave Latham (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-8770) deletes and puts with the same ts should be resolved according to mvcc/seqNum
Date Tue, 06 Jun 2017 16:41:18 GMT

    [ https://issues.apache.org/jira/browse/HBASE-8770?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16039224#comment-16039224

Dave Latham commented on HBASE-8770:

> We will remove mvcc in HFile in minor compaction (to save capacity) and delete/put will
have same mvcc if they are in one same file.

I think that would be OK so long as we first order by seq id, then order Put ahead of Delete
for the same seq id.  If we're compacting to an HFile, and the Put has higher seq id than
the Delete, write them both, and the Put will stay visible.  If the Delete has a higher seq
id than the Put, then just drop the Put as it should never be visible.  Would that work or
am I missing something?

However, if we do switch to always keeping the seq id around, then the point is moot.  Except
for the next case of an atomic RowMutation with Put and Delete having the same seq id.  Then
we have to make a call ont he semantic.  I think it's more useful to favor the Put over the
Delete (would solve HBASE-8626 also).

> deletes and puts with the same ts should be resolved according to mvcc/seqNum
> -----------------------------------------------------------------------------
>                 Key: HBASE-8770
>                 URL: https://issues.apache.org/jira/browse/HBASE-8770
>             Project: HBase
>          Issue Type: Brainstorming
>            Reporter: Sergey Shelukhin
>            Priority: Critical
> This came up during HBASE-8721. Puts with the same ts are resolved by seqNum. It's not
clear why deletes with the same ts as a put should always mask the put, rather than also being
resolve by seqNum.
> What do you think?

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