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https://issues.apache.org/jira/browse/HBASE-6427?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13424449#comment-13424449
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Lars Hofhansl commented on HBASE-6427:
--------------------------------------
Interestingly I would like to have the ability to bypass the default action
from both preFlush and preCompact, for example to control how the store files
are written.
With the new hooks there is no way to indicate that (null means "create the
default scanner", non-null means use the returned scanner, but still follow the
default action).
The hook just prior to creating the scanner could create a new scanner (and
hence decide how to filter the inputs) the hook right after scanner creation
could then control how/where to write the store files.
So maybe have a preCompactScannerOpen, and preFlushScannerOpen (similar to my
initial idea), and not deprecating the existing hooks?
> 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
>
>
> 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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