count of composite columns

(2 posts) (2 voices)

• Started 1 year ago by
• Latest reply from thepaul
• This topic is not resolved

Tags:

• composite count example
• composites
• CQL

1. 

   Anonymous
   Unregistered

   I need to keep a count of handed out tokens per some cross concern view. Tokens are handed out by a master, and the count is per master, so I decided for the following CF setup using composite columns:

   Usage = {
   L0000001: {
   (AAA, L0000001_0005_n1234_20120302_1): "2110-12-31T23:59:00+00:00"
   (AAA, L0000001_0005_n1234_20120302_2): "2110-12-31T23:59:00+00:00"
   (AAA, L0000001_0005_n1234_20120302_3): "2110-12-31T23:59:00+00:00"
   ...
   (BBB, L0000001_0005_n1234_20120302_1): "2110-12-31T23:59:00+00:00"
   (BBB, L0000001_0005_n1234_20120302_2): "2110-12-31T23:59:00+00:00"
   (BBB, L0000001_0005_n1234_20120302_3): "2110-12-31T23:59:00+00:00"
   ...
   }

   'L0000001' is the master, 'AAA' and 'BBB' are the cross concern views. Because the write will be high, I decided to use time-to-live to have to columns automatically clean up.

   What I now need is a way to count the number of living columns, so for for example L000001->AAA.

   1. Since these are composite columns, I don't think I can define an index on the first part of a column.
   2. CQL does not yet support composite columns, but if it does, then I cannot find a good example.
   2. I can't find an example of how to do get_count using composite columns.

   Posted 1 year ago #
2. 

   thepaul
   Moderator

   CQL does support composite columns. You probably want to read http://www.datastax.com/dev/blog/schema-in-cassandra-1-1 and http://www.datastax.com/dev/blog/whats-new-in-cql-3-0 for deeper information, but here's an example that might match what you have there:

   
CREATE TABLE Usage (
master ascii,
cross_concern_view ascii,
ccv_id ascii,
when timestamp,
PRIMARY KEY (master, cross_concern_view, ccv_id)
) WITH COMPACT STORAGE;

   SELECT count(*) FROM Usage WHERE master = 'L0000001' and cross_concern_view = 'AAA';


   Posted 1 year ago #

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