Thank you for your answer, and sorry about the sloppy terminology. I'm thinking of the scenario where there are a small number of results in the result set, but there are billions of rows in the first of your secondary indexes.
That is, I want to do something like (not sure of the CQL syntax): select * where type=2 and e=5 where there are billions of rows of type 2, but some manageable number of those rows have e=5. As I understand it, secondary indexes are like column families, where each value is a column. So the billions of rows where type=2 would go into a single row of the secondary index. This sounds like a problem to me, is it? I'm assuming that the billions of rows that don't have column "e" at all (those rows of other types) are not a problem at all... On Thu, Apr 14, 2011 at 12:12 PM, aaron morton <aa...@thelastpickle.com>wrote: > Need to clear up some terminology here. > > Rows have a key and can be retrieved by key. This is *sort of* the primary > index, but not primary in the normal RDBMS sense. > Rows can have different columns and the column names are sorted and can be > efficiently selected. > There are "secondary indexes" in cassandra 0.7 based on column values > http://www.datastax.com/dev/blog/whats-new-cassandra-07-secondary-indexes > > So you could create secondary indexes on the a,e, and h columns and get > rows that have specific values. There are some limitations to secondary > indexes, read the linked article. > > Or you can make your own secondary indexes using row keys as the index > values. > > If you have billions of rows, how many do you need to read back at once? > > Hope that helps > Aaron > > On 14 Apr 2011, at 04:23, David Boxenhorn wrote: > > Is it possible in 0.7.x to have indexes on heterogeneous rows, which have > different sets of columns? > > For example, let's say you have three types of objects (1, 2, 3) which each > had three members. If your rows had the following pattern > > type=1 a=? b=? c=? > type=2 d=? e=? f=? > type=3 g=? h=? i=? > > could you index "type" as your primary index, and also index "a", "e", "h" > as secondary indexes, to get the objects of that type that you are looking > for? > > Would it work if you had billions of rows of each type? > > >
