cassandra primary key

cassandra – natural vs surrogate primary key

corerootz - Ravi Kiran Krovvidi NoSQL - Cassandra, HBase

Using natural or surrogate primary keys

One consideration is whether to use surrogate or natural keys for a table. A surrogate key is a generated key (such as a UUID) that uniquely identifies a row, but has no relation to the actual data in the row.

For some tables, the data may contain values that are guaranteed to be unique and are not typically updated after a row is created. For example, the user name in a users table. This is called a natural key. Natural keys make the data more readable and remove the need for additional indexes or denormalization. However, unless your client application ensures uniqueness, it could potentially overwrite column data.

cassandra – composite primary key

corerootz - Ravi Kiran Krovvidi NoSQL - Cassandra, HBase

Defining a primary key column 

The only schema information that must be defined for a table is the primary key and its associated data type. Unlike earlier versions, CQL 3 does not require a column in the table that is not part of the primary key. A primary key can have any number (1 or more) of component columns.

If the primary key consists of only one column, you can use the keywords, PRIMARY KEY, after the column definition:

CREATE TABLE users (
  user_name varchar PRIMARY KEY,
  password varchar,
  gender varchar,
  session_token varchar,
  state varchar,
  birth_year bigint
);

Alternatively, you can declare the primary key consisting of only one column in the same way as you declare a compound primary key. Do not use a counter column for a key.

Using a compound primary key 

A compound primary key consists of more than one column. Cassandra treats the first column declared in a definition as the partition key. To create a compound primary key, use the keywords, PRIMARY KEY, followed by the comma-separated list of column names enclosed in parentheses.

CREATE TABLE emp (
  empID int,
  deptID int,
  first_name varchar,
  last_name varchar,
  PRIMARY KEY (empID, deptID)
);