Michael, this is HBase developers mailing list. -Vladimir
On Fri, Sep 12, 2014 at 12:08 AM, Michael Segel <[email protected]> wrote: > Silly question… > > HBase uses the term RLL (row level locking) to make the writes to a row > atomic. > > When you start to get in to isolation, RLL takes on a different meaning. > > So now you have to better define what do you mean by locking. Are you > taking about HBase RLL, > or are you talking about Transactional RLL ( RDBMS RLL) ? > > > On Sep 11, 2014, at 11:58 PM, Vladimir Rodionov <[email protected]> > wrote: > > > Hi, all > > > > We have two isolation levels in (used to be in Scan) in Query now. See: > > https://issues.apache.org/jira/browse/HBASE-11936 > > > > I moved isolation levels API from Scan upward to Query class. The reason: > > this API was not available for Get operations. The rationals? Improve > > performance of get and multi-gets over the same region. > > > > As many of you aware, RegionScannerImpl is heavily synchronized on > internal > > region's lock. Now some questions: > > > > 1. Is it safe to bypass this locking (in next() call) in READ_UNCOMMITTED > > mode? > > We will do all necessary checks, of course, before calling nextRaw(). > > 2. What was the reason of this locking in a first place for reads in > > READ_COMMITTED mode? Except obvious - no-dirty-reads allowed? Can someone > > tell me what else bad can happen? > > > > -Vladimir > >
