[
https://issues.apache.org/jira/browse/HBASE-13378?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14572024#comment-14572024
]
Andrew Purtell commented on HBASE-13378:
----------------------------------------
bq. Up to this point READ_UNCOMMITED meant: You might see partially finished
rows. Now it means: You might see partially finished rows, and you may not see
cells that have existed when the scanner started.
I'd be ok with this change in 0.98 with a release note describing the change in
semantics. In either case the user is asking for increased possible concurrency
in exchange for 'dirty' reads. What this patch does is alter a bit how dirty is
dirty, depending. (smile) I'm not sure what [~enis] or [~ndimiduk] would want
to do wrt. 1.0 and 1.1, or [~busbey] for 1.2.
> 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 so
> that READ_UNCOMMITTED does not synchronize.
> {CODE:JAVA}
> // synchronize on scannerReadPoints so that nobody calculates
> // getSmallestReadPoint, before scannerReadPoints is updated.
> IsolationLevel isolationLevel = scan.getIsolationLevel();
> synchronized(scannerReadPoints) {
> this.readPt = getReadpoint(isolationLevel);
> scannerReadPoints.put(this, this.readPt);
> }
> {CODE}
> This hotspots for me under heavy get requests.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
