CQL for Cassandra 1.2

Using the map type

As its name implies, a map maps one thing to another. A map is a name and a pair of typed values. Using the map type, you can store timestamp-related information in user profiles. Each element of the map is internally stored as one Cassandra column that you can modify, replace, delete, and query. Each element can have an individual time-to-live and expire when the TTL ends.

Procedure

  1. Add a todo list to every user profile in an existing users table using the CREATE TABLE or ALTER statement, specifying the map collection and enclosing the pair of data types in angle brackets.
    ALTER TABLE users ADD todo map<timestamp, text>
  2. Set or replace map data, using the INSERT or UPDATE command, and enclosing the timestamp and text values in a map collection: curly brackets, separated by a colon.
    UPDATE users
      SET todo =
      { '2012-9-24' : 'enter mordor',
      '2012-10-2 12:00' : 'throw ring into mount doom' }
      WHERE user_id = 'frodo';
  3. Set a specific element using the UPDATE command, enclosing the timestamp of the element in square brackets, and using the equals operator to map the value to that timestamp.
    UPDATE users SET todo['2012-10-2 12:00'] = 'throw my precious into mount doom'
      WHERE user_id = 'frodo';
  4. Use INSERT to specify data in a map collection.
    INSERT INTO users (todo)
      VALUES ( { '2013-9-22 12:01'  : 'birthday wishes to Bilbo',
      '2013-10-1 18:00' : 'Check into Inn of Prancing Pony' });
    Inserting this data into the map replaces the entire map
  5. Delete an element from the map using the DELETE command and enclosing the timestamp of the element in square brackets:
    DELETE todo['2012-9-24'] FROM users WHERE user_id = 'frodo';
  6. Retrieve the todo map.
    SELECT user_id, todo FROM users WHERE user_id = 'frodo';
    The order of the map output depends on the type of the map.
  7. Compute the TTL to use to expire todo list elements on the day of the timestamp, and set the elements to expire.
    UPDATE users USING TTL <computed_ttl>
      SET todo['2012-10-1'] = 'find water' WHERE user_id = 'frodo';
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