Data Modeling Approaches for Big Data and Analytics Solutions - Big Data Imperatives - page 184

The basic elements of the Cassandra data model are as follows:

• Column

• Super Column

• Column Family

• Keyspace

• Cluster

Column: A column is the basic unit of Cassandra data model. A column comprises
name, value and a time stamp (by default). An example of column in JSON format is as
follows:

{ // Example of Column
"name": "EmployeeID",
"value": "10029277",
"timestamp": 123456789
}

Super Column: A super column is a dictionary of boundless number of columns,
identified by the column name. An example of a super column in JSON format is as
follows:

{ // Example of Super Column
"name": "Specialization",
"value": {
"role" : {
"name": "role", "value": "Master Technology Architect", "timestamp":
123456789
},
"designation" : {
"name": "designation", "value": "Managing Director", "timestamp": 123456789
}
}

The major differences between a column and a super column are:

• Column's value is a string but the super column's value is a record

of columns.

• A super column doesn't include any time stamp (only term's

name and value).

■ Cassandra does not index sub-columns, so when a super column is loaded into
memory, all of its columns are loaded as well.

Note