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From "Jonathan Gray (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-2406) Define semantics of cell timestamps/versions
Date Wed, 08 Sep 2010 17:32:35 GMT

    [ https://issues.apache.org/jira/browse/HBASE-2406?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12907328#action_12907328
] 

Jonathan Gray commented on HBASE-2406:
--------------------------------------

Following commit of HBASE-1485, I think cell version semantics are basically defined.  You
can update existing versions and you can write versions out of order.

What is left is dealing with deletes.  I think there is some consensus that whether or not
we eventually "fix" this issue (inserting behind deletes), it's well beyond the scope of 0.90.

Since this JIRA deals with documentation, I suppose we should add a section to the book about
versions and then we can close this.  JIRAs remain to deal with the delete issue specifically.

Any volunteers?

> 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
>            Assignee: Pranav Khaitan
>            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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