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From Marcelo Elias Del Valle <mvall...@gmail.com>
Subject Re: 1000's of column families
Date Thu, 27 Sep 2012 14:45:39 GMT
Dean,

     I was used, in the relational world, to use hibernate and O/R mapping.
There were times when I used 3 classes (2 inheriting from 1 another) and
mapped all of the to 1 table. The common part was in the super class and
each sub class had it's own columns. The table, however, use to have all
the columns and this design was hard because of that, as creating more
subclasses would need changes in the table.
     However, if you use playOrm and if playOrm has/had a feature to allow
inheritance mapping to a CF, it would solve your problem, wouldn't it? Of
course it is probably much harder than it might problably appear... :D

Best regards,
Marcelo Valle.

2012/9/27 Hiller, Dean <Dean.Hiller@nrel.gov>

> We have 1000's of different building devices and we stream data from these
> devices.  The format and data from each one varies so one device has
> temperature at timeX with some other variables, another device has CO2
> percentage and other variables.  Every device is unique and streams it's
> own data.  We dynamically discover devices and register them.  Basically,
> one CF or table per thing really makes sense in this environment.  While we
> could try to find out which devices "are" similar, this would really be a
> pain and some devices add some new variable into the equation.  NOT only
> that but researchers can register new datasets and upload them as well and
> each dataset they have they do NOT want to share with other researches
> necessarily so we have security groups and each CF belongs to security
> groups.  We dynamically create CF's on the fly as people register new
> datasets.
>
> On top of that, when the data sets get too large, we probably want to
> partition a single CF into time partitions.  We could create one CF and put
> all the data and have a partition per device, but then a time partition
> will contain "multiple" devices of data meaning we need to shrink our time
> partition size where if we have CF per device, the time partition can be
> larger as it is only for that one device.
>
> THEN, on top of that, we have a meta CF for these devices so some people
> want to query for streams that match criteria AND which returns a CF name
> and they query that CF name so we almost need a query with variables like
> select cfName from Meta where x = y and then select * from cfName where
> xxxxx. Which we can do today.
>
> Dean
>
> From: Marcelo Elias Del Valle <mvallebr@gmail.com<mailto:
> mvallebr@gmail.com>>
> Reply-To: "user@cassandra.apache.org<mailto:user@cassandra.apache.org>" <
> user@cassandra.apache.org<mailto:user@cassandra.apache.org>>
> Date: Thursday, September 27, 2012 8:01 AM
> To: "user@cassandra.apache.org<mailto:user@cassandra.apache.org>" <
> user@cassandra.apache.org<mailto:user@cassandra.apache.org>>
> Subject: Re: 1000's of column families
>
> Out of curiosity, is it really necessary to have that amount of CFs?
> I am probably still used to relational databases, where you would use a
> new table just in case you need to store different kinds of data. As
> Cassandra stores anything in each CF, it might probably make sense to have
> a lot of CFs to store your data...
> But why wouldn't you use a single CF with partitions in these case?
> Wouldn't it be the same thing? I am asking because I might learn a new
> modeling technique with the answer.
>
> []s
>
> 2012/9/26 Hiller, Dean <Dean.Hiller@nrel.gov<mailto:Dean.Hiller@nrel.gov>>
> We are streaming data with 1 stream per 1 CF and we have 1000's of CF.
>  When using the tools they are all geared to analyzing ONE column family at
> a time :(.  If I remember correctly, Cassandra supports as many CF's as you
> want, correct?  Even though I am going to have tons of funs with
> limitations on the tools, correct?
>
> (I may end up wrapping the node tool with my own aggregate calls if needed
> to sum up multiple column families and such).
>
> Thanks,
> Dean
>
>
>
> --
> Marcelo Elias Del Valle
> http://mvalle.com - @mvallebr
>



-- 
Marcelo Elias Del Valle
http://mvalle.com - @mvallebr

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