If there is no objection, I will create a JIRA to increase the maximum number of column families described here:
http://hbase.apache.org/book.html#number.of.cfs Cheers On Mon, Apr 8, 2013 at 7:21 AM, Doug Meil <doug.m...@explorysmedical.com>wrote: > > > For the record, the refGuide mentions potential issues of CF lumpiness > that you mentioned: > > http://hbase.apache.org/book.html#number.of.cfs > > > 6.2.1. Cardinality of ColumnFamilies > > Where multiple ColumnFamilies exist in a single table, be aware of the > cardinality (i.e., number of rows). > If ColumnFamilyA has 1 million rows and ColumnFamilyB has 1 billion > rows, ColumnFamilyA's data will likely be spread > across many, many regions (and RegionServers). This makes mass > scans for ColumnFamilyA less efficient. > > > > > > Š. anything that needs to be updated/added for this? > > > > > > On 4/8/13 12:39 AM, "lars hofhansl" <la...@apache.org> wrote: > > >I think the main problem is that all CFs have to be flushed if one gets > >large enough to require a flush. > >(Does anyone remember why exactly that is? And do we still need that now > >that the memstoreTS is stored in the HFiles?) > > > > > >So things are fine as long as all CFs have roughly the same size. But if > >you have one that gets a lot of data and many others that are smaller, > >we'd end up with a lot of unnecessary and small store files from the > >smaller CFs. > > > >Anything else known that is bad about many column families? > > > > > >-- Lars > > > > > > > >________________________________ > > From: Andrew Purtell <apurt...@apache.org> > >To: "user@hbase.apache.org" <user@hbase.apache.org> > >Sent: Sunday, April 7, 2013 3:52 PM > >Subject: Re: schema design: rows vs wide columns > > > >Is there a pointer to evidence/experiment backed analysis of this > >question? > >I'm sure there is some basis for this text in the book but I recommend we > >strike it. We could replace it with YCSB or LoadTestTool driven latency > >graphs for different workloads maybe. Although that would also be a big > >simplification of 'schema design' considerations, it would not be so > >starkly lacking background. > > > >On Sunday, April 7, 2013, Ted Yu wrote: > > > >> From http://hbase.apache.org/book.html#number.of.cfs : > >> > >> HBase currently does not do well with anything above two or three column > >> families so keep the number of column families in your schema low. > >> > >> Cheers > >> > >> On Sun, Apr 7, 2013 at 3:04 PM, Stack <st...@duboce.net <javascript:;>> > >> wrote: > >> > >> > On Sun, Apr 7, 2013 at 11:58 AM, Ted <yuzhih...@gmail.com > >><javascript:;>> > >> wrote: > >> > > >> > > With regard to number of column families, 3 is the recommended > >>maximum. > >> > > > >> > > >> > How did you come up w/ the number '3'? Is it a 'hard' 3? Or does it > >> > depend? If the latter, on what does it depend? > >> > Thanks, > >> > St.Ack > >> > > >> > > > > > >-- > >Best regards, > > > > - Andy > > > >Problems worthy of attack prove their worth by hitting back. - Piet Hein > >(via Tom White) > > > >
