Database Reference
In-Depth Information
sandra is still in constant heavy development, and new features are always being
added and tested.
Note
The central paper on Cassandra, written by the primary Facebook
engineers, is called “Cassandra—A Decentralized Structured Stor-
age System” and is available at
www.cs.cornell.edu/projects/ladis-
Schema-less (If You Want)
Cassandra ColumnFamilys are considered schema-less. This means that you do
not need to define a schema ahead of time. If you want to add a column, you
simply specify the column name at write-time and the column will be created if it
doesn't exist. This lends itself to allowing for extremely wide rows, even rows that
have millions of columns. Additionally, rows do not need to contain all or even
any of the columns that other rows in the same table contain.
Cassandra does give you the option to create a schema, however. If you know
what your data structure looks like, you can add column names and specify default
types for those columns. This also enables you to add secondary indexes for the
columns that you know about.
Who Uses Cassandra?
Cassandra is in wide use around the world, and usage is growing all the time.
Companies like Netflix, eBay, Twitter, Reddit, and Ooyala all use Cassandra to
power pieces of their architecture, and it is critical to the day-to-day operations of
those organizations. To date, the largest publicly known Cassandra cluster by ma-
chine count has over 300TB of data spanning 400 machines.
Because of Cassandra's ability to handle high-volume data, it works well for a
myriad of applications. This means that it's well suited to handling projects from
the high-speed world of advertising technology in real time to the high-volume
world of big-data analytics and everything in between. It is important to know
your use case before moving forward to ensure things like proper deployment and
good schema design.
