Real time analytics with cassandra

Question

I watched this video on doing analystics with cassandra. I was pretty interested in the segment from 12.10 to 15.10

I didn't understand the last row key Θ , what did it signify. And given that all row keys are the where clauses and all cf are groub by clauses, how does region (UK,US) came in CF for row key Θ

Answer 1

So this is a super late reply, but I was looking for resources on Cassandra for analytics.

When you build an OLAP table, you aggregate over a particular dimension's values, in their example its the time. So in your table you might have

Hour  Somethings   Other things
0     6            34
1     8            44
2     5            27
3     5            52
...   ...          ...
24    6            42

The last entry, Θ, represents the sum of all of the above, so you can read it like the total of the columns, so that table might be

Hour  Somethings   Other things
0     6            34
1     8            44
2     5            27
3     5            52
...   ...          ...
24    6            42
Θ     144          960

(144 is the total number of somethings, and 960 of other things). I made up all these numbers btw, they don't appear in the video.