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https://issues.apache.org/jira/browse/HBASE-6427?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13424669#comment-13424669
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Andrew Purtell commented on HBASE-6427:
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bq. I understand the goal for this JIRA and am in support of it. [...] This
illustrates the intricacies of scanner chaining. If a scanner is designed for
some specific purpose, I wouldn't expect it to function correctly when an
arbitrary number of scanners are chained (both) upstream and downstream.
Pardon Ted but I think this is an X-Y argument. I'm not sure we are discussing
the chaining of _arbitrary_ scanners (unless I have this wrong.) Each CP hook
is dealing with a constrained set of scanners. Flushes will be dealing with
memstore scanners. Compactions will be dealing with store scanners. The
question has been what kind of interface should input parameters and return
types share, there's some design give-and-take there. But we are not talking
about, for example, combining memstore scanners with store scanners. (At least,
I am not.)
> 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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