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https://issues.apache.org/jira/browse/HBASE-8721?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13678994#comment-13678994
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Feng Honghua commented on HBASE-8721:
-------------------------------------
This fix uses mvcc together with timestamp to determine if a put will be masked
by a delete. So the put happened after a delete can't be masked by that delete
though according to timestamp it will be masked(before this fix). In this theme
mvcc will be kept intact unconditionally (not set to 0) when doing
flush/compact, and furthermore mvcc also need to be serialized(and later
unserialized) to HLog for possible replay, and max mvcc in recovered split HLog
also need to be reflected in the recovered HRegion during its initializing
phase.
> 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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