At some point joins may be necessary when denormalization is not possible. There is no built-in mechanism to do it. It would be a series of additional Get calls to the second table you are joining against. This would be helped significantly with a parallel MultiGet which will hopefully make it to 0.21.
JG > -----Original Message----- > From: TuX RaceR [mailto:[email protected]] > Sent: Friday, March 19, 2010 8:41 AM > To: [email protected] > Subject: Re: How to join tables in HBase 20.3 > > Hi Raffi, > > when dealing with key-value stores, you need to think in a different > way > see for instance: > > http://wiki.apache.org/hadoop/Hbase/DataModel > > "Getting high scalability from your relational database isn't done by > simply adding more machines because its data model is based on a > single-machine architecture. For example, a JOIN between two tables is > done in memory and does not take into account the possibility that the > data has to go over the wire." > > JOIN simply does not scale in relational databases. > > > see also > > http://wiki.apache.org/hadoop/Hbase/FAQ#A20 > > *20 Are there any Schema Design examples?* > > > Hope this helps, > > Cheers > TuX > > > Basmajian, Raffi wrote: > > I am new to HBase and come from a rdbms background. After looking in > the > > sample client code it seems fairly easy to query a single table using > > Get and Scan, but it's not so obvious how to join data across > multiple > > tables. > > > > Are there any examples on how to read/join data across multiple > tables? > > > > Thank you > > > > Raffi Basmajian > > > > > > --------------------------------------------------------------------- > --------- > > This e-mail transmission may contain information that is proprietary, > privileged and/or confidential and is intended exclusively for the > person(s) to whom it is addressed. Any use, copying, retention or > disclosure by any person other than the intended recipient or the > intended recipient's designees is strictly prohibited. If you are not > the intended recipient or their designee, please notify the sender > immediately by return e-mail and delete all copies. OppenheimerFunds > may, at its sole discretion, monitor, review, retain and/or disclose > the content of all email communications. > > > ======================================================================= > ======= > > > >
