My initial implementation of the Hot Rod based dialect doesn't support storing of unordered bags, as I followed the example from the Cassandra dialect which stated in a comment that it is not possible to persist such objects in a key/value store as there is lack of a key definition.

Emmanuel Bernard suggested that this could actually be done by adding a surrogate UUID to the row key: https://github.com/hibernate/hibernate-ogm/pull/766#issuecomment-246623915

I think that could work, and in addition if we were to support embedding collections - like storing all entries of the Bag in the same row key - this should also not be a problem.

I actually think that Bags should be stored as an embedded collection by default, and possibly as only mapping option, so to avoid the UUID overhead.