I think what you're describing might give me what I'm after, but I don't see how I can pass different column slices in a multiget call. I may be missing something, but it looks like you pass multiple keys but only a singular SlicePredicate. Please let me know if that's not what you meant.

I'm aware of CQL3 collections, but I don't think they quite suite my needs in this case.

Thanks for the suggestions!


On Fri, Sep 14, 2012 at 1:56 AM, aaron morton <aaron@thelastpickle.com> wrote:
You _could_ use one wide row and do a multiget against the same row for different column slices. Would be less efficient than a single get against the row. But you could still do big contiguous column slices. 

You may get some benefit from the collections in CQL 3 http://www.datastax.com/dev/blog/cql3_collections

Hope that helps. 

Aaron Morton
Freelance Developer

On 14/09/2012, at 8:31 AM, Adam Holmberg <adam.holmberg.list@gmail.com> wrote:

I'm modeling a new application and considering the use of SuperColumn vs. Composite Column paradigms. I understand that SuperColumns are discouraged in new development, but I'm pondering a query where it seems like SuperColumns might be better suited.

Consider a CF with SuperColumn layout as follows

t = {
  k1: {
    s1: { c1:v1, c2:v2 },
    s2: { c1:v3, c2:v4 },
    s3: { c1:v5, c2:v6}

Which might be modeled in CQL3:

  k text,
  s text,
  c1 text,
  c2 text,
  PRIMARY KEY (k, s)

I know that it is possible to do range slices with either approach. However, with SuperColumns I can do sparse slice queries with a set (list) of column names as the SlicePredicate. I understand that the composites API only returns contiguous slices, but I keep finding myself wanting to do a query as follows:

SELECT * FROM t WHERE k = 'foo' AND s IN (1,3);

The question: Is there a recommended technique for emulating sparse column slices in composites?

One suggestion I've read is to get the entire range and filter client side. This is pretty punishing if the range is large and the second keys being queried are sparse. Additionally, there are enough keys being queried that calling once per key is undesirable.

I also realize that I could manually composite k:s as the row key and use multiget, but this gives away the benefit of having these records proximate when range queries are used.

Any input on modeling/query techniques would be appreciated.

Adam Holmberg

What this seems like to me is a desire for 'multiget' at the second key level analogous to multiget at the row key level. Is this something that could be implemented in the server using SlicePredicate.column_names? Is this just an implementation gap, or is there something technical I'm overlooking?