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From "Hiller, Dean" <Dean.Hil...@nrel.gov>
Subject Re: Is Cassandra right for me?
Date Tue, 18 Sep 2012 13:04:07 GMT
I wanted to clarify the where that statement comes from on wide rows ….

Realize some people make the claim that if you don’t' have 1000's of columns in "some" rows
in cassandra you are doing something wrong.  This is not true, BUT it comes from the fact
that people are setting up indexes.  This is what leads to the very wide row affect.  playOrm
is one such library using wide rows like this BUT it is NOT necessary for all applications.

You can easily use map/reduce on a cassandra cluster.  You can map/reduce your dataset into
a new model if you make a mistake as well and don't get it right the first time.  This wide
row affect is 80% of the time used for indexing.  I draw off playOrm examples a lot but one
table may be partitioned by time so each month of data is in a partition, you can then have
indexes on each partition allowing you to do quick queries into partitions.

Later,
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: Monday, September 17, 2012 4:28 PM
To: "user@cassandra.apache.org<mailto:user@cassandra.apache.org>" <user@cassandra.apache.org<mailto:user@cassandra.apache.org>>
Subject: Is Cassandra right for me?

Hello,

     I am new to Cassandra and I am in doubt if Cassandra is the right technology to use in
the architecture I am defining. Also, I saw a presentation which said that if I don't have
rows with more than a hundred rows in Cassandra, whether I am doing something wrong or I shouldn't
be using Cassandra. Therefore, it might be the case I am doing something wrong. If you could
help me to find out the answer for these questions by giving any feedback, it would be highly
appreciated.
     Here is my need and what I am thinking in using Cassandra for:

 *   I need to support a high volume of writes per second. I might have a billion writes per
hour
 *   I need to write non-structured data that will be processed later by hadoop processes
to generate structured data from it. Later, I index the structured data using SOLR or SOLANDRA,
so the data can be consulted by my end user application. Is Cassandra recommended for that,
or should I be thinking in writting directly to HDFS files, for instance? What's the main
advantage I get from storing data in a nosql service like Cassandra, when compared to storing
files into HDFS?
 *   Usually I will write json data associated to an ID and my hadoop processes will process
this data to write data to a database. I have two doubts here:
    *   If I don't need to perform complicated queries in Cassandra, should I store the json-like
data just as a column value? I am afraid of doing something wrong here, as I would need just
to store the json file and some more 5 or 6 fields to query the files later.
    *   Does it make sense to you to use hadoop to process data from Cassandra and store the
results in a database, like HBase? Once I have structured data, is there any reason I should
use Cassandra instead of HBase?

     I am sorry if the questions are too dummy, I have been watching a lot of videos and reading
a lot of documentation about Cassandra, but honestly, more I read more I have questions.

Thanks in advance.

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

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