A counter is a special column for storing a number that is changed in
increments.
To load data into a counter column, or to increase or decrease the value of the
counter, use the UPDATE command. Cassandra rejects USING TIMESTAMP or USING TTL in
the command to update a counter column.
Procedure
-
Create a table for the counter column.
cqlsh> USE cycling;
CREATE TABLE popular_count (
id UUID PRIMARY KEY,
popularity counter
);
-
Loading data into a counter column is different than other tables. The data is
updated rather than inserted.
UPDATE cycling.popular_count
SET popularity = popularity + 1
WHERE id = 6ab09bec-e68e-48d9-a5f8-97e6fb4c9b47;
-
Take a look at the counter value and note that popularity
has a value of 1.
SELECT * FROM cycling.popular_count;
-
Additional increments or decrements will change the value of the counter
column.