Database Reference
In-Depth Information
Creating a keyspace
A
keyspace
is a collection of related tables, equivalent to a database in a relational system.
To create the keyspace for our MyStatus application, issue the following statement in the
CQL shell:
CREATE KEYSPACE "my_status"
WITH REPLICATION = {
'class': 'SimpleStrategy', 'replication_factor': 1
};
Here we created a keyspace called
my_status
, which we will use for the remainder of
this topic. When we create a keyspace, we have to specify replication options. Cassandra
provides several strategies for managing replication of data;
SimpleStrategy
is the
best strategy as long as your Cassandra deployment does not span multiple data centers.
The
replication_factor
value tells Cassandra how many copies of each piece of
data are to be kept in the cluster; since we are only running a single instance of Cassandra,
there is no point in keeping more than one copy of the data. In a production deployment,
you would certainly want a higher replication factor; 3 is a good place to start.
Note
A few things at this point are worth noting about CQL's syntax:
• It's syntactically very similar to SQL; as we further explore CQL, the impression
of similarity will not diminish.
• Double quotes are used for identifiers such as keyspace, table, and column names.
As in SQL, quoting identifier names is usually optional, unless the identifier is a
keyword or contains a space or another character that will trip up the parser.
• Single quotes are used for string literals; the key-value structure we use for replica-
tion is a
map
literal, which is syntactically similar to an object literal in JSON.
• As in SQL, CQL statements in the CQL shell must terminate with a semicolon.
