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https://issues.apache.org/jira/browse/HBASE-6427?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13424672#comment-13424672
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Lars Hofhansl commented on HBASE-6427:
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bq. This illustrates the intricacies of scanner chaining.
I think that is a false transitive statement. :)
For this particular hook chaining is hard, because this is an intricate part of
the HBase code. That does not mean that chaining is generally hard (it is not).
bq. I wouldn't expect it to function correctly when an arbitrary number of
scanners are chained (both) upstream and downstream.
Same here... The point is: It is possible to chain region observers even in
this case.
If that is not desired an implementer can break the chain (via the passed
context. and by ignoring the InternalScanner argument).
> 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-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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