Wiki / Configuration Parameters

Sets the maximum number of workers that can be started by a single Gather or Gather Merge node. Parallel workers are taken from the pool of processes established by max_worker_processes, limited by max_parallel_workers. Note that the requested number of workers may not actually be available at run time. If this occurs, the plan will run with fewer workers than expected, which may be inefficient. The default value is 2. Setting this value to 0 disables parallel query execution. Note that parallel queries may consume very substantially more resources than non-parallel queries, because each worker process is a completely separate process which has roughly the same impact on the system as an additional user session. This should be taken into account when choosing a value for this setting, as well as when configuring other settings that control resource utilization, such as work_mem. Resource limits such as work_mem are applied individually to each worker, which means the total utilization may be much higher across all processes than it would normally be for any single process. For example, a parallel query using 4 workers may use up to 5 times as much CPU time, memory, I/O bandwidth, and so forth as a query which uses no workers at all. For more information on parallel query, see Chapter 15.

English manual coverage begins with PostgreSQL 7.4. Source history and runtime observations have their own recorded version boundaries.

boot val

2

category

Resource Usage / Worker Processes

context

user

documented

true

enumvals

Unknown

extra desc

Unknown

lang

en

max val

1024

metadata version

18

min val

0

name

max_parallel_workers_per_gather

short desc

Sets the maximum number of parallel processes per executor node.

source

pg-settings-source-snapshot

unit

Unknown

vartype

integer