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Date: Fri, 4 Mar 2011 00:11:36 +0000 (UTC)
From: "Ted Yu (JIRA)" <jira@apache.org>
To: issues@hbase.apache.org
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Subject: [jira] Commented: (HBASE-3588) Proposal to optimize
 ReadWriteConsistencyControl
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    [ https://issues.apache.org/jira/browse/HBASE-3588?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13002344#comment-13002344 ] 

Ted Yu commented on HBASE-3588:
-------------------------------

The following change in MemStore would make TestHeapSize pass:
{code}
  public final static long FIXED_OVERHEAD = ClassSize.align(
      ClassSize.OBJECT + (12 * ClassSize.REFERENCE));
{code}


> Proposal to optimize ReadWriteConsistencyControl
> ------------------------------------------------
>
>                 Key: HBASE-3588
>                 URL: https://issues.apache.org/jira/browse/HBASE-3588
>             Project: HBase
>          Issue Type: Improvement
>          Components: regionserver
>            Reporter: dhruba borthakur
>            Assignee: dhruba borthakur
>         Attachments: rwcc.trunk.1, rwcc.trunk.1
>
>
> The ReadWriteConsistencyControl (RWCC) mechanism facilitates making a set of memstore updates atomically visible to readers. Also, the rwcc.completeMemstoreInsert() blocks till the memstore read point advances to the current writeNumber. This is done to ensure that if an application that does a put immediately issues a new get call for the same key, then the get should see the values inserted by the previous call to put. The current implementation assumes this worst-case and penalizes the put rpc to not return to the client until the read point advances to this transaction's write number.
> In many use-cases, the application never actually issues a get for the most recent put that it inserted. In this case, it would be nice if we can transfer the penalty (of blocking) to the get call that follows the initial put.

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