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From "stack (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 05:32:18 GMT

    [ https://issues.apache.org/jira/browse/HBASE-8770?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16038211#comment-16038211

stack commented on HBASE-8770:

bq. 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.

We should not do this, right?

bq. At least we should always keep mvcc in HFiles just like HBASE-15968 does.


bq. But we need more tests (I am testing in our own cluster) and I am not sure if it can be
a default behavior because the performance will be a little worse and a new feature may have
some bugs... And I am not sure if the patch is still right if we compare mvcc first before
type. Need more checking.

This sounds like an argument for committing it early. The perf downgrade I can see because
mvcc/sequenceid is unfortunately a second-class citizen at least until HLC is done.  Thats
tough. But the stuff about needs more checking and maybe bugs we should be able to live with.
Correctness first. Perf is secondary. What you think [~yangzhe1991]?

> 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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