Cassandra, user messages under a date

Question

Still trying to understand Cassandra I want users to see list of messages under a date they received from other users in this format below

CREATE TABLE user_messages (
    userid bigint,
    messages LIST<FROZEN<message>>,
    creation_date text,
    PRIMARY KEY (userid, creation_date)
);
.............8/3/2018...................
name: victor
content: ********

name: kelly
content: ******
.............7/3/2018...................
name: Vicky
content: *******
.............6/3/2018...................
name: Vicky
content: *******

If this design is correct how can i handle the insert operation?
Everytime a user wants to send message to a user do i need to check first if the userid and date exist if no insert, if yes i update the table to add the message inside the message list column.

Answer 1

Every time a user send a message to a user, use update statement like below

• User 2 send message to user 1

UPDATE user_messages 
     SET messages = messages + [{sender:2, message:'A'}] 
     WHERE userid = 1 AND creation_date = '2018-03-08';

• User 3 send message to user 1

UPDATE user_messages 
     SET messages = messages + [{sender:3, message:'B'}] 
     WHERE userid = 1 AND creation_date = '2018-03-08';

• User 1 get all message send by others

SELECT * FROM user_messages WHERE userid = 1 AND creation_date = '2018-03-08';

Output :

 userid | creation_date | messages
--------+---------------+--------------------------------------------------------
      1 |    2018-03-08 | [{sender: 2, message: 'A'}, {sender: 3, message: 'B'}]