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From "ramkrishna.s.vasudevan (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-17373) Reverse the order of snapshot creation in the CompactingMemStore
Date Wed, 04 Jan 2017 05:27:58 GMT

    [ https://issues.apache.org/jira/browse/HBASE-17373?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15797224#comment-15797224
] 

ramkrishna.s.vasudevan commented on HBASE-17373:
------------------------------------------------

[~eshcar]
I could spend more time in the logic and today I got the time to do it. I can see the purpose
 now. So before removing the snapshot has to be assigned and later we could remove the snapshot.
So by the time the scanner is created there are chances that the snapshot could be in pipeline
and in snapshot - so we will iterate twice but it is ok. 
But just an opinion - the swap was used to make use of existing code - but still in this case
where only the tail has to be removed - removeLast() is much faster than saying removeAll
which has to iterate and then remove. 
After removing the unused code it is quite easier to read the patch and it helps a lot. Thanks.

> Reverse the order of snapshot creation in the CompactingMemStore
> ----------------------------------------------------------------
>
>                 Key: HBASE-17373
>                 URL: https://issues.apache.org/jira/browse/HBASE-17373
>             Project: HBase
>          Issue Type: Sub-task
>            Reporter: Anastasia Braginsky
>            Assignee: Eshcar Hillel
>             Fix For: 2.0.0
>
>         Attachments: HBASE-17373-V01.patch, HBASE-17373-V02.patch, HBASE-17373-V03.patch,
HBASE-17373-V04.patch, HBASE-17373-V04.patch, HBASE-17373-V05.patch
>
>
> In CompactingMemStore both in BASIC and EAGER cases when snapshot is created the segments
are first removed from the pipeline then added to the snapshot. This is the opposite to what
is done in the DefaultMemStore where the snapshot is firstly created with the active segment
and only after the active segment is refreshed. This JIRA is about to reverse the order in
CompactingMemStore and to make all MemStores to behave the same.



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