ALTER TOPIC

You can use the ALTER TOPIC command to change the topic settings, as well as add, update, or delete its consumers.

Here is the general format of the ALTER TOPIC command:

ALTER TOPIC topic_path action1, action2, ..., actionN;

action is one of the alter actions described below.

Updating a set of consumers

ADD CONSUMER: Adds a consumer to a topic.

The following example will add a consumer with default settings to the topic.

ALTER TOPIC `my_topic` ADD CONSUMER new_consumer;

When adding consumers, you can specify their settings, for example:

ALTER TOPIC `my_topic` ADD CONSUMER new_consumer2 WITH (important = false);

important: Defines an important consumer. No data will be deleted from the topic until all the important consumers read them. Value type: boolean, default value: false.
read_from: Sets up the message write time starting from which the consumer will receive data. Data written before this time will not be read. Value type: Datetime OR Timestamp OR integer (unix-timestamp in the numeric format). Default value: now.

DROP CONSUMER: Deletes the consumer from the topic.

ALTER TOPIC `my_topic` DROP CONSUMER old_consumer;

ALTER CONSUMER: Adds a consumer for a topic.

Here is the general syntax for ALTER CONSUMER:

ALTER TOPIC `topic_name` ALTER CONSUMER consumer_name consumer_action;

Supports the following types of consumer_action:

The following example will assign the important parameter to the consumer.

ALTER TOPIC `my_topic` ALTER CONSUMER my_consumer SET (important = true);

You can specify several ALTER CONSUMER statements for a consumer. However, the settings applied by them shouldn't
repeat.

This is a valid statement:

ALTER TOPIC `my_topic`
    ALTER CONSUMER my_consumer SET (important = true)
    ALTER CONSUMER my_consumer SET (read_from = 0);

But this statement will raise an error.

ALTER TOPIC `my_topic`
    ALTER CONSUMER my_consumer SET (important = true)
    ALTER CONSUMER my_consumer SET (important = false);

Using the SET (option = value[, ...]) action, you can update your topic settings.

The example below will change the retention period for the topic and the writing quota per partition:

ALTER TOPIC `my_topic` SET (
    retention_period = Interval('PT36H'),
    partition_write_speed_bytes_per_second = 3000000
);

min_active_partitions: Minimum number of topic partitions. During automatic load balancing, the number of active partitions will not decrease below this value. Value type: integer, default value: 1.
partition_count_limit: Maximum number of active partitions in the topic. 0 is interpreted as unlimited. Value type: integer, default value: 0.
retention_period: Data retention period in the topic. Value type: Interval, default value: 18h.
retention_storage_mb: Limit on the maximum disk space occupied by the topic data. When this value is exceeded, the older data is cleared, like under a retention policy. 0 is interpreted as unlimited. Value type: integer, default value: 0
partition_write_speed_bytes_per_second: Maximum allowed write speed per partition. If a write speed for a given partition exceeds this value, the write speed will be capped. Value type: integer, default value: 2097152 (2MB).
partition_write_burst_bytes: Write quota allocated for write bursts. When set to zero, the actual write_burst value is equalled to the quota value (this allows write bursts of up to one second). Value type: integer, default value: 0.
metering_mode: Resource metering mode (RESERVED_CAPACITY - based on the allocated resources or REQUEST_UNITS - based on actual usage). This option applies to topics in serverless databases. Value type: String.

The following command sets the autopartitioning strategy to UP:

ALTER TOPIC `my_topic` SET (
    min_active_partitions = 1,
    max_active_partitions = 5,
    auto_partitioning_strategy = 'scale_up'
);

The following command pauses the topic autopartitioning:

ALTER TOPIC `my_topic` SET (
    auto_partitioning_strategy = 'paused'
);

The following command unpauses the topic autopartitioning:

ALTER TOPIC `my_topic` SET (
    auto_partitioning_strategy = 'scale_up'
);