Cassandra sets or composite columns

Question

I am storing account information in Cassandra. Each account has lists of data associated with it. For example, an account may have a list of friends and a list of liked books. Queries on accounts will always want all friends or all liked books or all of both. No filtering or searching is needed on either. The list of friends and books can grow and shrink.

Is it better to use a set column type or composite columns for this scenario?

Answer 1

I would suggest you not to use sets if

1. You are concerned about disk space(as each value is allocated a cell in disk + data space for metadata of each cell which is 15 bytes if am not wrong. Now that consumes a lot if your data is a growing one).

2. Not going to grow a lot of data in that particular row as each time ,the cells are to be fetched from different sstable .

In these kind of cases, the more preferred option would be a json array. You shall store it as a text and back the data from that.

Set (or any other collections ) use case was brought in for a completely different perspective. If you are having a particular value inside the list or a value has to be updated frequently inside the same collection, you shall make use of the collections .

My take on your query will be this.

Store all account specific info in a json object of friends that has a value as list of books .