I've updated the wiki page at
http://wiki.apache.org/cassandra/Cassandra2474 with a more in-depth
Background section that hopefully clears up where I'm going with this
sparse/dense business.
Eric mentioned on IRC that he's uneasy about the PRIMARY KEY syntax
implicitly using the first element of PRIMARY KEY as the row key. We
could make it explicit with another WITH option to the TRANSPOSED
clause:
{{{
CREATE TABLE timeline (
user_id int,
posted_at uuid,
column string,
value blob,
PRIMARY KEY(user_id, posted_at)
) TRANSPOSED WITH ROW KEY(user_id)
}}}
This makes things more verbose (this would be a required clause) but
I'm okay with that if consensus is that being explicit here is better.
