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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-8721) fix for bug that delete can mask puts that happened after the delete was entered
Date Tue, 11 Jun 2013 21:06:20 GMT

    [ https://issues.apache.org/jira/browse/HBASE-8721?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13680676#comment-13680676
] 

stack commented on HBASE-8721:
------------------------------

[~fenghh] On keeping deleted cells, it is an option I believe.  See http://hbase.apache.org/book.html#cf.keep.deleted

[~fenghh] Agree that the way delete works is uncanny where we could a put after a delete will
go unseen.

Thank you for looking into this.

You are using mvcc when rather it should be sequenceid that you should be using?  Is that
so?  mvcc is used cloaking memstore state doing a reveal only after all that makes up a transaction
has been written across the row.  sequenceid is given when we add something to the WAL and
it used ensuring ordering when doing WAL replays.
                
> fix for bug that delete can mask puts that happened after the delete was entered
> --------------------------------------------------------------------------------
>
>                 Key: HBASE-8721
>                 URL: https://issues.apache.org/jira/browse/HBASE-8721
>             Project: HBase
>          Issue Type: Bug
>          Components: regionserver
>            Reporter: Feng Honghua
>         Attachments: HBASE-8721-0.94-V0.patch
>
>
> this fix aims for bug mentioned in http://hbase.apache.org/book.html 5.8.2.1:
> "Deletes mask puts, even puts that happened after the delete was entered. Remember that
a delete writes a tombstone, which only disappears after then next major compaction has run.
Suppose you do a delete of everything <= T. After this you do a new put with a timestamp
<= T. This put, even if it happened after the delete, will be masked by the delete tombstone.
Performing the put will not fail, but when you do a get you will notice the put did have no
effect. It will start working again after the major compaction has run. These issues should
not be a problem if you use always-increasing versions for new puts to a row. But they can
occur even if you do not care about time: just do delete and put immediately after each other,
and there is some chance they happen within the same millisecond."

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