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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-6427) Pluggable policy for smallestReadPoint in HRegion
Date Wed, 25 Jul 2012 21:02:34 GMT

    [ https://issues.apache.org/jira/browse/HBASE-6427?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13422609#comment-13422609

Lars Hofhansl commented on HBASE-6427:

Yet another way of looking at is new coprocessor hook.
That would be a hook that sits before the StoreScanner is created (in Store.internalFlushCache
and Store.compact) and be passed the set of scanners to use, the store and whether this is
a major compaction or not (in the compaction case). Then this hook could optionally return
a scanner, and if non-null scanner is return that will be used for the flush/compaction.

Now, there already are preFlush and preCompact hooks (interestingly the preFlush is at the
region level, whereas the preCompact is at the store level, which is not quite right I think,
I wonder whether we can change that), so I'm having a hard time naming these hooks accordingly.
"preScannerFlush", "preScannerCompact" doesn't quite sound right.

[~apurtell] Do you have an opinion?

> Pluggable policy for smallestReadPoint in HRegion
> -------------------------------------------------
>                 Key: HBASE-6427
>                 URL: https://issues.apache.org/jira/browse/HBASE-6427
>             Project: HBase
>          Issue Type: New Feature
>            Reporter: Lars Hofhansl
>            Priority: Minor
> 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.
> 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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