Task properties#


  • Type: integer

  • Restrictions: must be a power of two

  • Default value: 16

Default local concurrency for parallel operators, such as joins and aggregations. This value should be adjusted up or down based on the query concurrency and worker resource utilization. Lower values are better for clusters that run many queries concurrently, because the cluster is already utilized by all the running queries, so adding more concurrency results in slow downs due to context switching and other overhead. Higher values are better for clusters that only run one or a few queries at a time. This can also be specified on a per-query basis using the task_concurrency session property.


  • Type: integer

  • Minimum value: 1

  • Default value: 100

Maximum number of threads that may be created to handle HTTP responses. Threads are created on demand and are cleaned up when idle, thus there is no overhead to a large value, if the number of requests to be handled is small. More threads may be helpful on clusters with a high number of concurrent queries, or on clusters with hundreds or thousands of workers.


  • Type: integer

  • Minimum value: 1

  • Default value: 3

Number of threads used to handle timeouts when generating HTTP responses. This value should be increased if all the threads are frequently in use. This can be monitored via the trino.server:name=AsyncHttpExecutionMBean:TimeoutExecutor JMX object. If ActiveCount is always the same as PoolSize, increase the number of threads.


  • Type: duration

  • Minimum value: 1ms

  • Maximum value: 10s

  • Default value: 3s

Controls staleness of task information, which is used in scheduling. Larger values can reduce coordinator CPU load, but may result in suboptimal split scheduling.


  • Type: data size

  • Default value: 16MB

Maximum size of partial aggregation results for distributed aggregations. Increasing this value can result in less network transfer and lower CPU utilization, by allowing more groups to be kept locally before being flushed, at the cost of additional memory usage.


  • Type: integer

  • Default value: Node CPUs * 2

Sets the number of threads used by workers to process splits. Increasing this number can improve throughput, if worker CPU utilization is low and all the threads are in use, but it causes increased heap space usage. Setting the value too high may cause a drop in performance due to a context switching. The number of active threads is available via the RunningSplits property of the trino.execution.executor:name=TaskExecutor.RunningSplits JMX object.


  • Type: integer

  • Default value: task.max-worker-threads * 2

The target number of running leaf splits on a worker. This is a minimum value because each leaf task is guaranteed at least 3 running splits. Non-leaf tasks are also guaranteed to run in order to prevent deadlocks. A lower value may improve responsiveness for new tasks, but can result in underutilized resources. A higher value can increase resource utilization, but uses additional memory.


  • Type: integer

  • Restrictions: must be a power of two

  • Default value: 1

The number of concurrent writer threads per worker per query. Increasing this value may increase write speed, especially when a query is not I/O bound and can take advantage of additional CPU for parallel writes. Some connectors can be bottlenecked on CPU when writing due to compression or other factors. Setting this too high may cause the cluster to become overloaded due to excessive resource utilization. This can also be specified on a per-query basis using the task_writer_count session property.