Writer scaling properties#
Writer scaling allows Trino to dynamically scale out the number of writer tasks rather than allocating a fixed number of tasks. Additional tasks are added when the average amount of physical data per writer is above a minimum threshold, but only if the query is bottlenecked on writing.
Writer scaling is useful with connectors like Hive that produce one or more files per writer – reducing the number of writers results in a larger average file size. However, writer scaling can have a small impact on query wall time due to the decreased writer parallelism while the writer count ramps up to match the needs of the query.
Enable writer scaling by dynamically increasing the number of writer tasks on the cluster.
Enable scaling the number of concurrent writers within a task. The maximum
writer count per task for scaling is task.max-writer-count. Additional
writers are added only when the average amount of uncompressed data processed
per writer is above the minimum threshold of
and query is bottlenecked on writing.
Type: data size
The minimum amount of uncompressed data that must be processed by a writer before another writer can be added.