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Date: Fri, 26 Oct 2012 20:43:12 +0000 (UTC)
From: "David Medinets (JIRA)" <jira@apache.org>
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Subject: [jira] [Commented] (ACCUMULO-803) Add Reverse Logical Time as a
 Time Type
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    [ https://issues.apache.org/jira/browse/ACCUMULO-803?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13485186#comment-13485186 ] 

David Medinets commented on ACCUMULO-803:
-----------------------------------------

I feel mucking with timestamps is asking for trouble. I'd rather see an effort to make the Key semantics changeable in a controlled fashion using a plug-in architecture. Then changes to support FIFO or other sorting mechanisms would use a well-defined API. Changes (and bugs) for each mechanism would be isolated.
                
> Add Reverse Logical Time as a Time Type
> ---------------------------------------
>
>                 Key: ACCUMULO-803
>                 URL: https://issues.apache.org/jira/browse/ACCUMULO-803
>             Project: Accumulo
>          Issue Type: Improvement
>          Components: tserver
>    Affects Versions: 1.5.0
>            Reporter: Drew Farris
>            Assignee: Drew Farris
>            Priority: Minor
>         Attachments: ACCUMULO-803.patch, ACCUMULO-803.patch
>
>
> In a context where we are doing aggregation/combination of multiple values for a given key it may be useful to iterate over the values associated with that key in the order in which the mutations were applied (FIFO), instead of the FILO order that seems to occur when using {{TimeType.LOGICAL}}. 
> I encountered when implemeting a checkAndPut operation that would ensure that the previous value was expected before putting a new value. In this case, if the previous value was not as expected, the mutation would be ignored. 
> Perhaps it is useful in a general case?

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