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From "Jonathan Gray (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-1263) Optimize for single-version families
Date Sun, 15 Mar 2009 07:14:50 GMT

    [ https://issues.apache.org/jira/browse/HBASE-1263?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12682131#action_12682131
] 

Jonathan Gray commented on HBASE-1263:
--------------------------------------

One idea would be to create a special KeyValue comparator that looked at row and column only
and ignored timestamp.

Stack, it still seems pretty clunky having different KV comparators that stores must be aware
of.  At least lots of branchy code at the beginning.  We also talked about potentially allowing
descending order or custom comparators... would there be a "simple" way to make the comparator
an additional and optional family setting?

> 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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