MultiVersionConsistencyControl.getThreadReadPoint() retrieves value from a ThreadLocal.
Can you specify which operation becomes expensive ? BTW I only found IsolationLevel.READ_UNCOMMITTED in TestRowProcessorEndpoint. Looks like it is not normally used. On Fri, Oct 11, 2013 at 2:20 PM, Vladimir Rodionov <[email protected]>wrote: > 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: [email protected] > > ________________________________________ > From: Vladimir Rodionov > Sent: Friday, October 11, 2013 2:18 PM > To: [email protected] > 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: [email protected] > > Confidentiality Notice: The information contained in this message, > including any attachments hereto, may be confidential and is intended to be > read only by the individual or entity to whom this message is addressed. If > the reader of this message is not the intended recipient or an agent or > designee of the intended recipient, please note that any review, use, > disclosure or distribution of this message or its attachments, in any form, > is strictly prohibited. If you have received this message in error, please > immediately notify the sender and/or [email protected] and > delete or destroy any copy of this message and its attachments. >
