cluster_table_* session settings

These settings are available in system.settings and are autogenerated from source.

cluster_table_function_buckets_batch_size

Defines the approximate size of a batch (in bytes) used in distributed processing of tasks in cluster table functions with bucket split granularity. The system accumulates data until at least this amount is reached. The actual size may be slightly larger to align with data boundaries.

cluster_table_function_split_granularity

Controls how data is split into tasks when executing a CLUSTER TABLE FUNCTION.

This setting defines the granularity of work distribution across the cluster:

• file — each task processes an entire file.
• bucket — tasks are created per internal data block within a file (for example, Parquet row groups).

Choosing finer granularity (like bucket) can improve parallelism when working with a small number of large files. For instance, if a Parquet file contains multiple row groups, enabling bucket granularity allows each group to be processed independently by different workers.