I am new to Cassandra and have a few novice level questions in the primary key.

1. Is the Primary key supposed to be unique per record? (My guess would be not.)
To elaborate. Suppose my table looks like this

```
    CREATE TABLE user_action (
    user_id int,
    action text,
    date_of_action date,
    PRIMARY KEY (user_id)
    )

```

I am guessing I can have multiple rows with the same `user_id`

2. If primary key is not one per record, can a primary key be split across many partitions?
3. Can a partition have multiple primary keys?
4. Is the primary key itself decided to pick the partition or is the hashCode of the primary key used to pick a partition?
5. Is it fair to think of a partition as a file?