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From tommaso barbugli <tbarbu...@gmail.com>
Subject Re: keyspace with hundreds of columnfamilies
Date Thu, 03 Jul 2014 19:55:18 GMT
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 <jack@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 <tbarbugli@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.hardouin@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 <tbarbugli@gmail.com> a écrit sur 02/07/2014 17:40:18 :
>>
>> > De : tommaso barbugli <tbarbugli@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.hardouin@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 <tbarbugli@gmail.com> a écrit sur 02/07/2014 10:13:41
>> :
>> >
>> > > De : tommaso barbugli <tbarbugli@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
>>
>
>

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