In a nut shell, aggregation group is a tool define partial cubes. nFull Cube nPre-aggregate all dimension combinations n“Curse of dimensionality”: N dimension cube has 2N cuboid. n nPartial Cube nTo avoid dimension explosion, we divide the dimensions into different aggregation groups n2N+M+L à 2N + 2M + 2L nFor cube with 30 dimensions, if we divide these dimensions into 3 group, the cuboid number will reduce from 1 Billion to 3 Thousands n230 à 210 + 210 + 210 nTradeoff between online aggregation and offline pre-aggregation
More info can be found here: http://www.slideshare.net/YangLi43/design-cube-in-apache-kylin Cheers On Fri, Apr 10, 2015 at 3:28 PM, [email protected] <[email protected]> wrote: > Hi, > > Recently adding to this mailing list. > > Should be good if can see some offical FAQ : ) > > Best, > Sun. > > > > [email protected] > > From: hongbin ma > Date: 2015-04-10 15:23 > To: dev > Subject: Re: RowKeyDesc aggregationGroups > @yang > > i remember you had a standard answer to this question. > shall we put it into FAQ? > > On Fri, Apr 10, 2015 at 3:21 PM, [email protected] <[email protected]> > wrote: > > > Hi, team > > > > Digging into kylin cube build engine and interested in rowkey build > > schema. One question: > > > > What does the aggregationGroups actually mean? Why it should be declared > > as 2-dimension array of String ? > > > > Hope for some expert guide. > > > > Thanks, > > Sun. > > > > > > > > [email protected] > > > > > -- > Regards, > > *Bin Mahone | 马洪宾* > Apache Kylin: http://kylin.io > Github: https://github.com/binmahone >
