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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-3656) Merging flush; merge a flush with one of the existing store files (the smallest?) so we skip creating a new store file on each flush
Date Thu, 04 Oct 2012 21:07:49 GMT

    [ https://issues.apache.org/jira/browse/HBASE-3656?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13469697#comment-13469697
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Lars Hofhansl commented on HBASE-3656:
--------------------------------------

This would (potentially) make certain backup solution more difficult.

Imagine a backup scheme that backs up each HFile resulting from a major compaction and each
HFile resulting from a flush (HFiles from minor compactions are not needed and just complicate
things).
This would no longer be possible since the flushed KVs would then be intermingled with other
KVs, which may or may not be in an HFile that was copied already.

Not saying this is a reason for not doing this.
                
> Merging flush; merge a flush with one of the existing store files (the smallest?) so
we skip creating a new store file on each flush
> ------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: HBASE-3656
>                 URL: https://issues.apache.org/jira/browse/HBASE-3656
>             Project: HBase
>          Issue Type: Task
>            Reporter: stack
>
> This behavior is described in the BT paper.  Years ago I had a go at it but at the time
it slowed flushing significantly -- and IIRC we had no barriers on writes when the memory
pressue was high -- so it brought on OOMEs... so punted on it.  Its time to consider this
feature again.
> Would we always do it?  Maybe not if its a close?  If a close we want stuff to run quickly
so we should skip the merge.  But any other time, we should do it?

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