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From "Erik Holstad (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-1263) Optimize for single-version families
Date Tue, 17 Mar 2009 19:04:50 GMT

    [ https://issues.apache.org/jira/browse/HBASE-1263?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12682761#action_12682761

Erik Holstad commented on HBASE-1263:

I totally agree that we should not have a system that have the same timestamp in multiple
places, that will brake the whole model
and will make earlying out impossible when we are doing that based on time. 
So if we go along with deleting entries from the memCache we could just let Delete(ts) delete
itself too if it finds that version in 
memcache, doing it like that means that we don't get any overhead of multiple versions and
extra deletes hanging out for no use.

> Optimize for single-version families
> ------------------------------------
>                 Key: HBASE-1263
>                 URL: https://issues.apache.org/jira/browse/HBASE-1263
>             Project: Hadoop HBase
>          Issue Type: New Feature
>          Components: regionserver
>            Reporter: Jonathan Gray
>             Fix For: 0.20.0
> As some of us have been discussing, allowing the client to manually set the timestamp
of a put breaks the general semantics of versioning and I'd like to see it removed as part
of HBASE-880 (a more appropriate place to debate that).
> However, one trick being used when you don't want the overhead of versions on a frequently
updated column (which are only cleared on compactions even if set to 1), was to use the same
timestamp.  Since that would create an identical key it would just overwrite the value not
create a new version.
> It's a very common use-case, and this hack is being used as part of the committed increment
ops from HBASE-868/HBASE-1252.  Rather than making a special optimization for counters, an
optimization on single-version families that never stores more than one version of a column.

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