[jira] Commented: (HBASE-1263) Optimize for single-version families

["Jonathan Gray (JIRA)" <ji...@apache.org>]

    [ 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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Re: [jira] Commented: (HBASE-1263) Optimize for single-version families

[Ryan Rawson <ry...@gmail.com>]

we should measure the efficiency gains at run time and compare with the
additional code complexity.

in a JIT Hotspot, the loss of performance might not be as high as we think.

-ryan

On Sat, Mar 14, 2009 at 11:14 PM, Jonathan Gray (JIRA) <ji...@apache.org>wrote:

>
>    [
> 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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> You can reply to this email to add a comment to the issue online.
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