If on, emit information about lightweight lock usage.
At a glance
| Property | Value |
|---|---|
| Parameter | trace_lwlocks |
| Category | Developer Options |
| Default | (see documentation) |
| Value type | boolean (on/off) |
| Change scope | Per-session (SET) |
| Available in | PostgreSQL 12, 13, 14, 15, 16, 17, 18, 19 (added in 12) |
What it does
If on, emit information about lightweight lock usage. Lightweight locks are intended primarily to provide mutual exclusion of access to shared-memory data structures.
This parameter is only available if the LOCK_DEBUG macro was defined when PostgreSQL was compiled.
(Description quoted from the official PostgreSQL documentation.)
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 trace_lwlocks; or SELECT name, setting, unit, context, source FROM pg_settings WHERE name = 'trace_lwlocks';.
Tuning guidance
This is a developer and debugging aid, not a performance knob. Leave it at the default in production; enable it only temporarily, on a non-production or carefully controlled system, while diagnosing a specific problem. Several options in this group add overhead, generate large volumes of log output, or can damage data if misused — turn them off again as soon as the investigation is done.