user to be able to change their mail address but then it may not be part of the primary key of a Cassandra table [closed]

I use Spring Boot 2.1.x to store a user entity in a Cassandra database. This works.

• java generated uuid
• mail address
• salted bcrypt password
• some user defined types...

In case somebody uses the login I get the mail and the password to get the credentials.

For retrieving the user object I expect some where clause with select * from user where username = mail.

However, mail must be the partition key in Cassandra, but I want the user to be able to change their mail address and then it may not be part of the primary key of a Cassandra table.

My naive bad idea is to have an inverse table with a tuple (mail, java generated uuid) to look up the user and then to load the user with the uuid.

@PrimaryKeyColumn(type = PrimaryKeyType.PARTITIONED, ordinal = 0, name = "id")
@JsonProperty("id")
private String id;

@PrimaryKeyColumn(type = PrimaryKeyType.CLUSTERED, ordinal = 1, name = "email")
@Email(message = "*Please provide a valid email")
@NotEmpty(message = "*Please provide an email")
@JsonProperty("email")
private String email;