[jira] [Commented] (HBASE-6427) Pluggable policy for smallestReadPoint in HRegion

["Lars Hofhansl (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-6427?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13418922#comment-13418922 ] 

Lars Hofhansl commented on HBASE-6427:
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Let me clarify what I mean by this:
If I wanted to implement an MVCC based optimistic transaction engine on top of HBase I would naturally want to use HBase's built in versioning (where possible).
In that case it is not clear a priori how many versions to keep or for how long (i.e. specifying VERSION/TTL is too static). The outside engine would need to determine that.
The simplest of all approaches would be to do that via the smallestReadpoint in each region, by making its determination pluggable.

                
> 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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