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From "stack (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-2406) Define semantics of cell timestamps/versions
Date Sun, 18 Jul 2010 21:45:50 GMT

    [ https://issues.apache.org/jira/browse/HBASE-2406?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12889687#action_12889687
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stack commented on HBASE-2406:
------------------------------

>From Bruno article, issues mentioned are:

+ Gets lack "...the ability to retrieve the latest version less than or equal to a given timestamp,
thus giving the 'latest' state of the record at a certain point in time."
+ Major compactions are not invisible to the user: "...create three cell versions at t1, t2
and t3, with a maximum-versions setting of 2. So when getting all versions, only the values
at t2 and t3 will be returned. But if you delete the version at t2 or t3, the one at t1 will
appear again. Obviously, once a major compaction has run, such behavior will not be the case
anymore..."
+ hbase-1485, where if two cells with same coordinates, we do not return latest added
+ A put after a tombstone was put in will be overshadowed by the tombstone if timestamp is
older than the tombstone, though it went in after the tombstone was added (I made an issue
for this, HBASE-2847).





> Define semantics of cell timestamps/versions
> --------------------------------------------
>
>                 Key: HBASE-2406
>                 URL: https://issues.apache.org/jira/browse/HBASE-2406
>             Project: HBase
>          Issue Type: Task
>          Components: documentation
>            Reporter: Todd Lipcon
>            Priority: Critical
>             Fix For: 0.90.0
>
>
> There is a lot of general confusion over the semantics of the cell timestamp. In particular,
a couple questions that often come up:
> - If multiple writes to a cell have the same timestamp, are all versions maintained or
just the last?
> - Is it OK to write cells in a non-increasing timestamp order?
> Let's discuss, figure out what semantics make sense, and then move towards (a) documentation,
(b) unit tests that prove we have those semantics.

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