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From "ramkrishna.s.vasudevan (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-17434) New Synchronization Scheme for Compaction Pipeline
Date Mon, 09 Jan 2017 11:55:58 GMT

    [ https://issues.apache.org/jira/browse/HBASE-17434?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15811602#comment-15811602

ramkrishna.s.vasudevan commented on HBASE-17434:

bq. may scan the same segment twice.
This is what I was interested. So one question - say the scan says 3 versions. Now due to
the above reason we scan the same segment twice. So we will send the same data again and say
we have read 3 versions? or because ts was same the internal scan will avoid counting the
duplicate as one new version?
Can you pls check this? 

> New Synchronization Scheme for Compaction Pipeline
> --------------------------------------------------
>                 Key: HBASE-17434
>                 URL: https://issues.apache.org/jira/browse/HBASE-17434
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Eshcar Hillel
>            Assignee: Eshcar Hillel
>         Attachments: HBASE-17434-V01.patch, HBASE-17434-V02.patch, HBASE-17434-V03.patch
> A new copyOnWrite synchronization scheme is introduced for the compaction pipeline.
> The new scheme is better since it removes the lock from getSegments() which is invoked
in every get and scan operation, and it reduces the number of LinkedList objects that are
created at runtime, thus can reduce GC (not by much, but still...).
> In addition, it fixes the method getTailSize() in compaction pipeline. This method creates
a MemstoreSize object which comprises the data size and the overhead size of the segment and
needs to be atomic.

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