Cassandra frozen keyword meaning

Question

What's the meaning of the frozen keyword in Cassandra?

I'm trying to read this documentation page: Using a user-defined type , but their explanation for the frozen keyword (which they use in their examples) is not clear enough for me:

To support future capabilities, a column definition of a user-defined or tuple type requires the frozen keyword. Cassandra serializes a frozen value having multiple components into a single value. For examples and usage information, see "Using a user-defined type", "Tuple type", and Collection type.

I haven't found any other definition or a clear explanation for that in the net.

Answer 1

In Cassandra if you define UDT or Collection as frozen, you can't update UDT's or collection's individual item, you have to reinsert with full value.

A frozen value serializes multiple components into a single value. Non-frozen types allow updates to individual fields. Cassandra treats the value of a frozen type as a blob. The entire value must be overwritten.

Source : https://docs.datastax.com/en/cql/3.1/cql/cql_reference/collection_type_r.html

@Alon : "Long story short: frozen = immutable"

Answer 2

For a user-defined type, I have noticed that you can update frozen the set by adding or removing the set elements. For example, let's say we create a table as follows.

create type rule_option_udt(display text, code text);
create TABLE rules (key text, options set<frozen<rule_option_udt>>, primary key (key));

As per the definition we expect that we won't be able to use + or - operation with the options field. But you can use add or remove operation as a normal set.

insert into rules (key, options) values ('fruits', {{display: 'Apple', code: 'apple'}})  ;

update rules set options = options + {{display: 'Orange', code: 'orange'}};

The above update is valid but you can't do the same with simple types such as text. I am not sure if this is expected nature or not but this is how it works for me.

In addition to this <frozen<set<udt>> && set<frozen<udt>> are behaving in the same manner. While describing the table you can see both are being shown as set<frozen<udt>>