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Date: Tue, 6 Jun 2017 16:41:18 +0000 (UTC)
From: "Dave Latham (JIRA)" <jira@apache.org>
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Subject: [jira] [Commented] (HBASE-8770) deletes and puts with the same ts
 should be resolved according to mvcc/seqNum
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archived-at: Tue, 06 Jun 2017 16:41:24 -0000


    [ 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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