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https://issues.apache.org/jira/browse/HBASE-6428?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13420741#comment-13420741
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Andrew Purtell edited comment on HBASE-6428 at 7/23/12 4:18 PM:
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Is there a use case where there could be multiple receivers for a
getSmallestReadPoint call? Where you want that kind of stacking, the CP API
upcall approach is good; where you have a global behavior that you might want
to override, a plug makes sense. For consistency's sake, those pluggable points
should all work the same way. We have HBASE-4050's ServiceLoader, but I think
we should also look at Guice (HBASE-6407).
Edit: Another consideration is performance. I'd like to draw a distinction
between coarse grained extension and fine grained extension. The former is
where large sections of functionality are replaced, for example using CPs to
replace default compaction selection with another strategy. The latter
certainly applies to single method calls on hot code paths. For the latter,
ideally we want an extension mechanism that will still allow the JVM to inline
what's plugged in.
was (Author: apurtell):
Is there a use case where there could be multiple receivers for a
getSmallestReadPoint call? Where you want that kind of stacking, the CP API
upcall approach is good; where you have a global behavior that you might want
to override, a plug makes sense. For consistency's sake, those pluggable points
should all work the same way. We have HBASE-4050's ServiceLoader, but I think
we should also look at Guice (HBASE-6407).
> Pluggable Compaction policies
> -----------------------------
>
> Key: HBASE-6428
> URL: https://issues.apache.org/jira/browse/HBASE-6428
> Project: HBase
> Issue Type: New Feature
> Reporter: Lars Hofhansl
>
> For some usecases is useful to allow more control over how KVs get compacted.
> For example one could envision storing old versions of a KV separate HFiles,
> which then rarely have to be touched/cached by queries querying for new data.
> In addition these date ranged HFile can be easily used for backups while
> maintaining historical data.
> This would be a major change, allowing compactions to provide multiple
> targets (not just a filter).
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