You're going to have a problem doing this in a single query because you're asking cassandra to select a non-contiguous set of rows. Also, to my knowledge, you can only use non equal operators on clustering keys. The best solution I could come up with would be to define you table like so:

CREATE TABLE room_data (
room_id uuid,
in_room int,
temp float,
time timestamp,
PRIMARY KEY (room_id, in_room, temp));

Then run 2 queries:
SELECT * FROM room_data WHERE in_room > 7;
SELECT * FROM room_data WHERE temp > 50.0;

And do an intersection on the results.

I should add the disclaimer that I am relatively new to CQL, so there may be a better way to do this.

Blake


On Wed, Nov 28, 2012 at 10:02 AM, Oren Karmi <okarmi@gmail.com> wrote:
Hi,

According to the documentation on Indexes ( http://www.datastax.com/docs/1.1/ddl/indexes ),
in order to use WHERE on a column which is not part of my key, I must define a secondary index on it. However, I can only use equality comparison on it but I wish to use other comparisons methods like greater than.

Let's say I have a room with people and every timestamp, I measure the temperature of the room and number of people. I use the timestamp as my key and I want to select all timestamps where temperature was over 50 degrees but I can't seem to be able to do it with a regular query even if I define that column as a secondary index.
SELECT * FROM MyTable WHERE temp > 50.4571;

My lame workaround is to define a secondary index on NumOfPeopleInRoom and than for a specific value
SELECT * FROM MyTable WHERE NumOfPeopleInRoom = 7 AND temp > 50.4571;

I'm pretty sure this is not the proper way for me to do this.

How should I attack this? It feels like I'm missing a very basic concept.
I'd appreciate it if your answers include also the option of not changing my schema.

Thanks!!!