Max parallel workers a single Gather node can use.
At a glance
| Property | Value |
|---|---|
| Parameter | max_parallel_workers_per_gather |
| Category | Parallelism |
| Default | 2 |
| Value type | boolean / enum / numeric |
| Change scope | Per-session (SET) |
What it does
Maximum number of parallel worker processes a single query node may launch. 0 disables parallel query for the session.
How to apply a change
Can be set per session with SET, per role/database with ALTER ROLE/DATABASE ... SET, or globally in postgresql.conf.
Inspect the current value and source with SHOW max_parallel_workers_per_gather; or SELECT name, setting, unit, context, source FROM pg_settings WHERE name = 'max_parallel_workers_per_gather';.
Tuning guidance
Raise (4-8) for analytical/reporting workloads on multi-core servers; keep modest for high-concurrency OLTP so many queries do not each grab workers. Bounded by max_parallel_workers and max_worker_processes.