thank you for the replies; I am rethinking the schema design, one possible solution is to "implode" one dimension and get N times less CFs. With this approach I would come up with (cql) tables with up to 100 columns; would that be a problem?
Thank You, Tommaso 2014-07-02 23:43 GMT+02:00 Jack Krupansky <j...@basetechnology.com>: > The official answer, engraved in stone tablets, and carried down from > the mountain: “Although having more than dozens or hundreds of tables > defined is almost certainly a Bad Idea (just as it is a design smell in a > relational database), it's relatively straightforward to allow disabling > the SlabAllocator.” Emphasis on “almost certainly a Bad Idea.” > > See: > https://issues.apache.org/jira/browse/CASSANDRA-5935 > “Allow disabling slab allocation” > > IOW, this is considered an anti-pattern, but... > > -- Jack Krupansky > > *From:* tommaso barbugli <tbarbu...@gmail.com> > *Sent:* Wednesday, July 2, 2014 2:16 PM > *To:* user@cassandra.apache.org > *Subject:* Re: keyspace with hundreds of columnfamilies > > Hi, > thank you for you replies on this; regarding the arena memory is this a > fixed memory allocation or is some sort of in memory caching? I ask because > I think that a substantial portion of the column families created will not > be queried that frequently (and some will become inactive and stay like > that really long time) > > Thank you, > Tommaso > > > 2014-07-02 18:35 GMT+02:00 Romain HARDOUIN <romain.hardo...@urssaf.fr>: > >> Arena allocation is an improvement feature, not a limitation. >> It was introduced in Cassandra 1.0 in order to lower memory fragmentation >> (and therefore promotion failure). >> AFAIK It's not intended to be tweaked so it might not be a good idea to >> change it. >> >> Best, >> Romain >> >> tommaso barbugli <tbarbu...@gmail.com> a écrit sur 02/07/2014 17:40:18 : >> >> > De : tommaso barbugli <tbarbu...@gmail.com> >> > A : user@cassandra.apache.org, >> > Date : 02/07/2014 17:40 >> > Objet : Re: keyspace with hundreds of columnfamilies >> > >> > 1MB per column family sounds pretty bad to me; is this something I >> > can tweak/workaround somehow? >> > >> > Thanks >> > Tommaso >> > >> >> > 2014-07-02 17:21 GMT+02:00 Romain HARDOUIN <romain.hardo...@urssaf.fr>: >> > The trap is that each CF will consume 1 MB of memory due to arena >> allocation. >> > This might seem harmless but if you plan thousands of CF it means >> > thousands of mega bytes... >> > Up to 1,000 CF I think it could be doable, but not 10,000. >> > >> > Best, >> > >> > Romain >> > >> > >> > tommaso barbugli <tbarbu...@gmail.com> a écrit sur 02/07/2014 10:13:41 >> : >> > >> > > De : tommaso barbugli <tbarbu...@gmail.com> >> > > A : user@cassandra.apache.org, >> > > Date : 02/07/2014 10:14 >> > > Objet : keyspace with hundreds of columnfamilies >> > > >> > > Hi, >> > > Are there any known issues, shortcomings about organising data in >> > > hundreds of column families? >> > > At this present I am running with 300 column families but I expect >> > > that to get to a couple of thousands. >> > > Is this something discouraged / unsupported (I am using Cassandra >> 2.0). >> > > >> > > Thanks >> > > Tommaso >> > >
