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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-6427) Pluggable compaction policies via coprocessors
Date Sat, 28 Jul 2012 22:36:34 GMT

    [ 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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