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https://issues.apache.org/jira/browse/HBASE-13378?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14547291#comment-14547291
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Lars Hofhansl commented on HBASE-13378:
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bq. "looks fine to me" is the oddest -1 I've ever seen.
Touché :)
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 finished
rows. Now it means: You might see partially finished rows, and you may not see
cells that have existed when the scanner started.
We never had the case before that a scanner could not see Cells that existed
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 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.
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