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https://issues.apache.org/jira/browse/HBASE-6427?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13425228#comment-13425228
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Lars Hofhansl commented on HBASE-6427:
--------------------------------------
Thanks Ted and Andy, and thanks for the discussion.
I think we have two (maybe three) take-aways: (1) We need to look at the
various scanner interface and see why we have so many diverging interfaces and
(2) add more coprocessor documentation (maybe with some more examples) and
potentially (3) think generally about what it means to extend HBase and when
coprocessors are a good mechanism for that.
It seems to me that coprocessors are a good solution to effect existing
processing at certain (including critical) spots, but maybe not suited to
replace the entire logic. In that this issue represents a corner case - which
is probably what spawned the longer discussion here (the creation of the
StoreScanner is replaced, and this is done in the context of a bigger
operation).
In the future we might be able to use Guice to replace entire subsystems.
For this issue I'll fix up the Javadoc issues that Ted mentions and commit this
to trunk and also make a 0.94 patch.
Thanks again for the review and the discussion.
> Pluggable compaction policies via coprocessors
> ----------------------------------------------
>
> Key: HBASE-6427
> URL: https://issues.apache.org/jira/browse/HBASE-6427
> Project: HBase
> Issue Type: New Feature
> Reporter: Lars Hofhansl
> Assignee: Lars Hofhansl
> Priority: Minor
> Attachments: 6427-notReady.txt, 6427-v1.txt, 6427-v10.txt,
> 6427-v2.txt, 6427-v3.txt, 6427-v4.txt, 6427-v5.txt, 6427-v7.txt
>
>
> When implementing higher level stores on top of HBase it is necessary to
> allow dynamic control over how long KVs must be kept around.
> Semi-static config options for ColumnFamilies (# of version or TTL) is not
> sufficient.
> This can be done with a few additional coprocessor hooks, or by makeing
> Store.ScanInfo pluggable.
> Was:
> The simplest way to achieve this is to have a pluggable class to determine
> the smallestReadpoint for Region. That way outside code can control what KVs
> to retain.
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