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 oka...@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!!!
