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Date: Sun, 17 May 2015 19:22:00 +0000 (UTC)
From: "Lars Hofhansl (JIRA)" <jira@apache.org>
To: issues@hbase.apache.org
Message-ID: <JIRA.12787367.1427901178000.138343.1431890520117@Atlassian.JIRA>
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 <JIRA.12787367.1427901178855@arcas>
Subject: [jira] [Commented] (HBASE-13378) RegionScannerImpl synchronized for
 READ_UNCOMMITTED Isolation Levels
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    [ https://issues.apache.org/jira/browse/HBASE-13378?page=3Dcom.atlassia=
n.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=3D145=
47291#comment-14547291 ]=20

Lars Hofhansl commented on HBASE-13378:
---------------------------------------

bq. "looks fine to me" is the oddest -1 I've ever seen.

Touch=C3=A9 :)

It's only a -1 until we all agree that the change in behavior is acceptable=
. Namely:
bq. Up to this point READ_UNCOMMITED meant: You might see partially finishe=
d rows. Now it means: You might see partially finished rows, and you may no=
t see cells that have existed when the scanner started.

We never had the case before that a scanner could not see Cells that existe=
d when it started.


> RegionScannerImpl synchronized for READ_UNCOMMITTED Isolation Levels
> --------------------------------------------------------------------
>
>                 Key: HBASE-13378
>                 URL: https://issues.apache.org/jira/browse/HBASE-13378
>             Project: HBase
>          Issue Type: New Feature
>            Reporter: John Leach
>            Assignee: John Leach
>            Priority: Minor
>         Attachments: HBASE-13378.patch, HBASE-13378.txt
>
>   Original Estimate: 2h
>          Time Spent: 2h
>  Remaining Estimate: 0h
>
> This block of code below coupled with the close method could be changed s=
o that READ_UNCOMMITTED does not synchronize. =20
> {CODE:JAVA}
>       // synchronize on scannerReadPoints so that nobody calculates
>       // getSmallestReadPoint, before scannerReadPoints is updated.
>       IsolationLevel isolationLevel =3D scan.getIsolationLevel();
>       synchronized(scannerReadPoints) {
>         this.readPt =3D getReadpoint(isolationLevel);
>         scannerReadPoints.put(this, this.readPt);
>       }
> {CODE}
> This hotspots for me under heavy get requests.


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