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Date: Thu, 22 Sep 2011 17:37:26 +0000 (UTC)
From: "Lars Hofhansl (JIRA)" <jira@apache.org>
To: issues@hbase.apache.org
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Subject: [jira] [Commented] (HBASE-4344) Persist memstoreTS to disk
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    [ https://issues.apache.org/jira/browse/HBASE-4344?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13112736#comment-13112736 ] 

Lars Hofhansl commented on HBASE-4344:
--------------------------------------

Hmm... See this code in SplitTransaction.java:
{code}
      case CLOSED_PARENT_REGION:
        // So, this returns a seqid but if we just closed and then reopened, we
        // should be ok. On close, we flushed using sequenceid obtained from
        // hosting regionserver so no need to propagate the sequenceid returned
        // out of initialize below up into regionserver as we normally do.
        // TODO: Verify.
        this.parent.initialize();
        break;
{code}

This is where it fails. Moving initialization of rwcc to HRegion.initialize rather then at construction time fixes this for me.


> Persist memstoreTS to disk
> --------------------------
>
>                 Key: HBASE-4344
>                 URL: https://issues.apache.org/jira/browse/HBASE-4344
>             Project: HBase
>          Issue Type: Sub-task
>            Reporter: Amitanand Aiyer
>            Assignee: Amitanand Aiyer
>             Fix For: 0.89.20100924
>
>         Attachments: 4344-v2.txt, 4344-v4.txt, 4344-v5.txt, 4344-v6.txt, patch-2
>
>
> Atomicity can be achieved in two ways -- (i) by using  a multiversion concurrency system (MVCC), or (ii) by ensuring that "new" writes do not complete, until the "old" reads complete.
> Currently, Memstore uses something along the lines of MVCC (called RWCC for read-write-consistency-control). But, this mechanism is not incorporated for the key-values written to the disk, as they do not include the memstore TS.
> Let us make the two approaches be similar, by persisting the memstoreTS along with the key-value when it is written to the disk.

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