RisingWave supports copy-on-write (CoW) mode for Iceberg tables and sinks. This is designed to ensure that external consumers always see a clean, delete-free snapshot of the data. Iceberg CoW mode uses two branches to separate ingestion from external queries. The ingestion-branch handles continuous writes, including data files and delete files, while the main-branch provides a clean, delete-free view for downstream applications.

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Scenario

Instead of leaving delete files for readers to merge in MoR mode, RisingWave periodically rewrites data files to absorb the deletes. This approach is ideal for workloads with frequent upserts where downstream systems require a stable and consistent view. The trade-off is higher write amplification and potential latency during compaction.

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Example

To use Copy-on-Write mode, set the parameter write_mode = 'copy-on-write' when creating your Iceberg table or sink.
Create an Iceberg table
CREATE TABLE t_copy_on_write (
    a INT PRIMARY KEY,
    b INT
) WITH (
    commit_checkpoint_interval = 10,
    compaction_interval_sec = 30,
    write_mode = 'copy-on-write'
) ENGINE = iceberg;
Create an Iceberg sink
CREATE SINK rest_sink FROM my_data
WITH (
    connector = 'iceberg',
    type = 'upsert',
    primary_key = 'id',
    warehouse.path = 's3://my-bucket/warehouse',
    database.name = 'my_database',
    table.name = 'my_table',
    catalog.type = 'rest',
    catalog.uri = 'http://rest-catalog:8181',
    catalog.credential = 'username:password',
    s3.access.key = 'your-access-key',
    s3.secret.key = 'your-secret-key',
    enable_compaction = true,
    write_mode = 'copy-on-write',
    commit_checkpoint_interval = 10,
    compaction_interval_sec = 30,
    enable_snapshot_expiration = true,
    snapshot_expiration_max_age_millis=0
);