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From Vladimir Rodionov <vrodio...@carrieriq.com>
Subject RE: skipKVsNewerThanReadpoint in StoreFileScanner and MemStoreScanner
Date Fri, 11 Oct 2013 21:20:50 GMT
Update.

This method is not called in MemStoreScanner, but direct call to : 

readPoint = MultiVersionConsistencyControl.getThreadReadPoint();

on every next, seek etc
which is basically the same.

All these calls become very expensive when you try to achieve 10s of millions RPS in scan
operations.

Best regards,
Vladimir Rodionov
Principal Platform Engineer
Carrier IQ, www.carrieriq.com
e-mail: vrodionov@carrieriq.com

________________________________________
From: Vladimir Rodionov
Sent: Friday, October 11, 2013 2:18 PM
To: dev@hbase.apache.org
Subject: skipKVsNewerThanReadpoint in StoreFileScanner and MemStoreScanner

>From HRegion:

synchronized(scannerReadPoints) {
        if (isolationLevel == IsolationLevel.READ_UNCOMMITTED) {
          // This scan can read even uncommitted transactions
          this.readPt = Long.MAX_VALUE;
          MultiVersionConsistencyControl.setThreadReadPoint(this.readPt);
        } else {
          this.readPt = MultiVersionConsistencyControl.resetThreadReadPoint(mvcc);
        }

If isolation level is READ_UNCOMMITTED than this method should never be called in both StoreFileScanner
and MemStoreScanner
If isolation level is READ_COMMITTED than this method must be called only in MemStoreScanner,
because HFiles are immutable no new KV's can be added
to HFile after StoreFileScanner was created.


Correct?


Best regards,
Vladimir Rodionov
Principal Platform Engineer
Carrier IQ, www.carrieriq.com
e-mail: vrodionov@carrieriq.com

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