How Can I Use the Counter Column?

Supported Operations

In open-source Cassandra, the counter column stores values as 64-bit signed integers which can only be incremented or decremented. In addition, GeminiDB Cassandra API provides the following functions:

• You can set values in the counter column.
• You can delete counters by column, row, range, and partition.
• Write performance of a table with counters will deteriorate if they are deleted by range and partition, so these functions are disabled by default.
• To delete values by range and partition, set counter_multiline_deletion_enabled to true.

Constraints

• A counter cannot be defined as a primary key.
• If a counter is used, all of the columns other than primary keys must be counters.
• TTL cannot be set for counters.
• INSERT cannot be executed for counters, which can only be inserted through UPDATE statements.

Example

CREATE TABLE t0(pk int, ck int, v1 counter, v2 counter, v3 counter, PRIMARY KEY(pk, ck));
# Writes counter columns. Sets values for v1, increments values for v2, and decrements values for v3.
UPDATE t0 SET v1 = 1, v2 = v2 + 1, v3 = v3 - 1 WHERE pk = 1 AND ck = 1;
# Deletes counters by column.
DELETE v1 FROM t0 where pk = 1 AND ck = 1;
# Deletes counters by row.
DELETE FROM t0 where pk = 1 AND ck = 1;