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From "Todd Lipcon (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-5311) Allow inmemory Memstore compactions
Date Tue, 07 Feb 2012 09:31:59 GMT

    [ https://issues.apache.org/jira/browse/HBASE-5311?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13202193#comment-13202193
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Todd Lipcon commented on HBASE-5311:
------------------------------------

Apparently this technique is called read-copy-update and the concurrency primitive is an RCU
lock. There might be a more clever way of implementing it in Java but it's already probably
over-optimized!
                
> Allow inmemory Memstore compactions
> -----------------------------------
>
>                 Key: HBASE-5311
>                 URL: https://issues.apache.org/jira/browse/HBASE-5311
>             Project: HBase
>          Issue Type: Improvement
>            Reporter: Lars Hofhansl
>         Attachments: InternallyLayeredMap.java
>
>
> Just like we periodically compact the StoreFiles we should also periodically compact
the MemStore.
> During these compactions we eliminate deleted cells, expired cells, cells to removed
because of version count, etc, before we even do a memstore flush.
> Besides the optimization that we could get from this, it should also allow us to remove
the special handling of ICV, Increment, and Append (all of which use upsert logic to avoid
accumulating excessive cells in the Memstore).
> Not targeting this.

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