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From "themanatuf@juno.com" <themana...@juno.com>
Subject Re: Cassandra basics
Date Sat, 24 Jul 2010 00:50:56 GMT
Sonia,

If you haven't visited the site below, I think it does the best job of explaining what Cassandra
is all about:

http://arin.me/blog/wtf-is-a-supercolumn-cassandra-data-model

Consider a group of ColumFamilies within a Keyspace like a group of tables in a database.

CompareWith tells Cassandra how to sort the data and it is sorted by the types you described.
So if you tell it to sort by UTF8Type it will consider the in the column that matches your
row key to be UTF8 data and will sort accordingly.



From: sonia gehlot <sonia.gehlot@gmail.com>
To: user@cassandra.apache.org
Subject: Cassandra basics
Date: Fri, 23 Jul 2010 15:48:12 -0700

Hi Guys,

Recently I have started reading about Cassandra from the material available on net. But I
have very confused with the basic understanding of Cassandra. 
I understand columnFamilies, supper columnFamilies but I have no clear understanding of


<Keyspace Name="Twitter">
  <ColumnFamily CompareWith="UTF8Type" Name="Statuses" />
  <ColumnFamily CompareWith="UTF8Type" Name="StatusAudits" />


  <ColumnFamily CompareWith="UTF8Type" Name="StatusRelationships" CompareSubcolumnsWith="TimeUUIDType"
ColumnType="Super" />  
  <ColumnFamily CompareWith="UTF8Type" Name="Users" />


  <ColumnFamily CompareWith="UTF8Type" Name="UserRelationships" CompareSubcolumnsWith="TimeUUIDType"
ColumnType="Super" />
</Keyspace>


<ColumnFamily Name = "LocationUserIndexSCF"
         CompareWith = "UTF8Types"
         CompareSubcolumnsWith= "UTF8Type"
         ColumnType = "Super"/> 

1. I don't understand what is this "CompareWith", "CompareSuperColumnWith", "CompareSubcolumnsWith"
etc is?

2. What is "UTF8Type", "TimeUUIDType", "LongType", "ASCIIType" etc.. is these are datatypes?
as we have datatype in SQL, if so then is this is datatype of value stored in this column
family?



May be I am getting confused because I am mixing my Relational databases fundamentals with
distributed.
Please If someone can explain me significance of these things then it would be very helpful.

Thanks in advance.

Please reply.

Sonia 


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