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https://issues.apache.org/jira/browse/HBASE-13378?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14581259#comment-14581259
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Lars Hofhansl commented on HBASE-13378:
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bq. Can someone explain this one to me?
The effect is on the READ_UNCOMMITTED scanner, this patch won't record it's
readpoint in scannerReadPoints, and flushes and compactions might let go of
Cells that are newer than the scanner's readpoint.
I actually think that is _OK_, I just wanted to consensus, it seems [~enis] and
[~ndimiduk] are not OK with it.
[~enis], [~ndimiduk], the behavior I described above would _only_ effect the
scanner declared with READ_UNCOMMITTED. Do you still think this is a
compatibility issue?
> 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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