ALTER FRAGMENT

The ALTER FRAGMENT command modifies the configuration of streaming fragments at runtime.

Syntax

ALTER FRAGMENT fragment_id [, ...]
    alter_option;

alter_option depends on the operation you want to perform on the fragment.

Clauses

SET PARALLELISM

ALTER FRAGMENT fragment_id [, ...]
SET PARALLELISM { TO | = } { parallelism_number | ADAPTIVE | DEFAULT };

Parameter or clause	Description
SET PARALLELISM	This clause controls the degree of parallelism for specific streaming fragments. This allows fine-grained control over fragment execution, enabling targeted scaling of individual fragments within a streaming job.
fragment_id	The ID of the fragment to modify. You can specify multiple fragment IDs separated by commas. To find fragment IDs, query the rw_fragment_parallelism system table.
parallelism_number	A fixed number (e.g., 1, 2, 3) that locks the fragment’s parallelism at that value. Setting it to 0 is equivalent to ADAPTIVE.
ADAPTIVE	Expands the fragment’s parallelism to all available units in the cluster.
DEFAULT	Resets the fragment’s parallelism to inherit from its parent streaming job’s parallelism setting.

Example

-- Set the parallelism of fragment 5 to 4
ALTER FRAGMENT 5 SET PARALLELISM = 4;

-- Set the parallelism of multiple fragments to adaptive
ALTER FRAGMENT 10, 11, 12 SET PARALLELISM = ADAPTIVE;

-- Reset fragment parallelism to inherit from the job
ALTER FRAGMENT 7 SET PARALLELISM = DEFAULT;

SET { SOURCE_RATE_LIMIT | BACKFILL_RATE_LIMIT | DML_RATE_LIMIT | SINK_RATE_LIMIT }

ALTER FRAGMENT fragment_id
SET { SOURCE_RATE_LIMIT | BACKFILL_RATE_LIMIT | DML_RATE_LIMIT | SINK_RATE_LIMIT } { TO | = } { DEFAULT | rate_limit_number };

Parameter or clause	Description
SET SOURCE_RATE_LIMIT	Controls the source rate limit for the specified fragment.
SET BACKFILL_RATE_LIMIT	Controls the backfill rate limit for the specified fragment.
SET DML_RATE_LIMIT	Controls the DML rate limit for the specified fragment.
SET SINK_RATE_LIMIT	Controls the sink rate limit for the specified fragment.
fragment_id	The ID of the fragment to modify. Only a single fragment ID is supported for this operation.
DEFAULT	Resets the selected rate limit to the default value.
rate_limit_number	The rate limit value in records per second. Set to 0 to pause the selected fragment activity.

SINK_RATE_LIMIT requires a sink with a KV log store. Set sink_decouple = true before creating the sink to enable sink decoupling. Each rate limit applies only to fragments containing the corresponding rate-limit operator.

ALTER FRAGMENT ... SET RATE_LIMIT ... remains supported as a backward-compatible alias for SET BACKFILL_RATE_LIMIT.

Example

-- Set backfill rate limit for fragment 3
ALTER FRAGMENT 3 SET BACKFILL_RATE_LIMIT = 1000;

-- Set sink rate limit for fragment 3
ALTER FRAGMENT 3 SET SINK_RATE_LIMIT = 500;

-- Pause backfilling for fragment 3
ALTER FRAGMENT 3 SET BACKFILL_RATE_LIMIT = 0;

-- Reset source rate limit for fragment 3
ALTER FRAGMENT 3 SET SOURCE_RATE_LIMIT = DEFAULT;

-- RATE_LIMIT is an alias for BACKFILL_RATE_LIMIT
ALTER FRAGMENT 3 SET RATE_LIMIT = 1000;

See also

• System catalogs — View fragment information using rw_fragment_parallelism and rw_fragments