Hi Robert, What about modelling it as a time serie?
CREATE TABLE document ( docId UUID, doc TEXT, last_modified TIMESTAMP PRIMARY KEY(docId, last_modified) ) WITH CLUSTERING ORDER BY (last_modified DESC); This way, you the lastest modification will always be the first record in the row, therefore accessing it should be as easy as: SELECT * FROM document WHERE docId == <the docId> LIMIT 1; And, if you experience diskspace issues due to very long rows, then you can always expire old ones using TTL or on a batch job. Tombstones will never be a problem in this case as, due to the specified clustering order, the latest modification will always be first record in the row. Hope it helps. Carlos Alonso | Software Engineer | @calonso <https://twitter.com/calonso> On 21 July 2015 at 05:59, Robert Wille <rwi...@fold3.com> wrote: > Data structures that have a recently-modified access pattern seem to be a > poor fit for Cassandra. I’m wondering if any of you smart guys can provide > suggestions. > > For the sake of discussion, lets assume I have the following tables: > > CREATE TABLE document ( > docId UUID, > doc TEXT, > last_modified TIMEUUID, > PRIMARY KEY ((docid)) > ) > > CREATE TABLE doc_by_last_modified ( > date TEXT, > last_modified TIMEUUID, > docId UUID, > PRIMARY KEY ((date), last_modified) > ) > > When I update a document, I retrieve its last_modified time, delete the > current record from doc_by_last_modified, and add a new one. Unfortunately, > if you’d like each document to appear at most once in the > doc_by_last_modified table, then this doesn’t work so well. > > Documents can get into the doc_by_last_modified table multiple times if > there is concurrent access, or if there is a consistency issue. > > Any thoughts out there on how to efficiently provide recently-modified > access to a table? This problem exists for many types of data structures, > not just recently-modified. Any ordered data structure that can be > dynamically reordered suffers from the same problems. As I’ve been doing > schema design, this pattern keeps recurring. A nice way to address this > problem has lots of applications. > > Thanks in advance for your thoughts > > Robert > >
