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When RisingWave streams data into Iceberg, it generates many small data files and creates frequent snapshots. Over time, this can degrade query performance and increase storage costs. To maintain healthy tables, RisingWave provides both automatic and manual maintenance features for compaction and snapshot expiration.
  • Compaction: Merges small data files and delete files into larger, optimized files to improve read performance.
  • Snapshot Expiration: Removes old, unneeded snapshots and their associated data files to reclaim storage space.
Automatic maintenance for Iceberg was added in RisingWave v2.5.0.

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Automatic maintenance

You can enable automatic maintenance to run periodically in the background for your Iceberg sinks and internal tables.
Dedicated Compactor RequiredAutomatic Iceberg maintenance requires a dedicated compactor service. Please contact us via the RisingWave Slack workspace to have the necessary resources allocated for your cluster.

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Parameters

Configure automatic maintenance by specifying the following parameters in the WITH clause of a CREATE SINK or CREATE TABLE ... ENGINE = iceberg statement.
ParameterDescription
enable_compactionRequired. Set to true to enable automatic compaction and snapshot expiration.
compaction_interval_secOptional. The interval in seconds between maintenance runs. Default: 3600.
enable_snapshot_expirationOptional. Set to true to enable snapshot expiration. By default, it removes snapshots older than 5 days.
snapshot_expiration_max_age_millisOptional. The maximum age (in milliseconds) for a snapshot to be retained. To keep only the latest snapshot, set this to 0.
snapshot_expiration_retain_lastOptional. The minimum number of snapshots to retain, regardless of their age.
max_snapshots_num_before_compactionOptional. The maximum number of snapshots allowed since the last rewrite operation. If set, the sink will pause if this number is exceeded until compaction completes.

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Examples

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Internal Iceberg table

CREATE TABLE my_iceberg_table (
    id INT PRIMARY KEY, 
    name VARCHAR
) WITH (
    enable_compaction = true, 
    compaction_interval_sec = 1800, 
    enable_snapshot_expiration = true,
    snapshot_expiration_retain_last = 10
) ENGINE = iceberg;

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Iceberg Sink

CREATE SINK my_iceberg_sink FROM my_mv
WITH (
    connector = 'iceberg',
    type = 'upsert',
    primary_key = 'id',
    warehouse.path = 's3://my-bucket/warehouse',
    database.name = 'my_db',
    table.name = 'my_table',
    catalog.type = 'rest',
    catalog.uri = 'http://rest-catalog:8181',
    s3.access.key = 'your-key',
    s3.secret.key = 'your-secret',
    -- Maintenance settings
    enable_compaction = true, 
    compaction_interval_sec = 1800, 
    enable_snapshot_expiration = true,
    snapshot_expiration_retain_last = 10
);

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Manual maintenance

In addition to automatic background maintenance, you can trigger compaction and snapshot expiration manually at any time using the VACUUM command. This gives you on-demand control over table optimization and storage cleanup. 
-- Compact small files for a table
VACUUM my_iceberg_table;

-- Compact files and expire snapshots older than 2 days
VACUUM my_iceberg_table RETAIN 2 DAYS;
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