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From "Sergey Shelukhin (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-8721) Deletes can mask puts that happen after the delete
Date Fri, 21 Jun 2013 17:11:22 GMT

    [ https://issues.apache.org/jira/browse/HBASE-8721?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13690482#comment-13690482
] 

Sergey Shelukhin commented on HBASE-8721:
-----------------------------------------

note that there are two arguments here, one is for real glitch with major compactions removing
the markers as described; and one for adding a delete with a semantic that will be internal
sequence-based and ignore put timestamps completely (previous-in-sequence puts removed, next-in-sequence
puts visible despite timestamps. By extension this delete semantic will obviously not have
the major-compaction-related glitch, but this is a side-effect, not the main argument for
such semantics.
Let's not conflate them...

                
> Deletes can mask puts that happen after the delete
> --------------------------------------------------
>
>                 Key: HBASE-8721
>                 URL: https://issues.apache.org/jira/browse/HBASE-8721
>             Project: HBase
>          Issue Type: Improvement
>          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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