session_preload_libraries

session_preload_libraries is the PostgreSQL setting that lists shared libraries to preload into each backend.

Note

Fact — official short description: “Lists shared libraries to preload into each backend.”

Identity

Type , Valuestring: Upstream pg_settings type
Context , Valuesuperuser: Settable at runtime by a superuser
Unit , Value—: Raw unit
Range , Value—: Raw limits in the last observed version
Enum values , Value—: — for non-enum types
Category , ValueClient Connection Defaults / Shared Library Preloading: Upstream classification
Latest boot value , Value"": empty string

Lifecycle

Fact	Value
First observed	PG9.4
Present in	PG9.4–19 Beta 3
Removed in	No
Introduction commit	`070518ddab2c` — Add session_preload_libraries configuration parameter
Commit date	2013-06-12
Discussion	—

Default history

Measured PG9.0–19 Beta 3 boot defaults
Versions	Raw `boot_val`	Unit	Human value
PG9.4–19 Beta 3	`""`	—	empty string

How it works

session_preload_libraries lists shared libraries to preload into each backend. The list is loaded into each new matching backend and may be set only by a superuser or an appropriately privileged role; a missing library rejects the connection.

Although session_preload_libraries is configurable without a server restart, its library list is acted on only when a new backend starts; changing it inside an established connection does not unload or retroactively load modules.

Library discovery and preloading interact with installed binary versions, extension control files, server or backend startup, and the module’s own GUCs.

Tuning advice

Tip

Advice. These are workload-specific starting points and must be validated with measurements.

Workload	Guidance
OLTP	Do not tune session_preload_libraries generically. Load or expose only modules required by a reviewed feature, verify binary compatibility, and rehearse failure recovery before rollout.
OLAP	Use session_preload_libraries for a measured extension or JIT requirement, accounting for backend startup, resident memory, and behavior under connection pooling.
Small nodes	Keep session_preload_libraries minimal. A missing or incompatible module can reject connections or prevent startup, and every preloaded library consumes scarce address space or memory.

Pigsty

Values use the fixed 8-vCPU, 32-GiB, 100-GiB SSD fixture and render the current Pigsty templates for PG19 Beta 3; this does not assert current Pigsty support for that historical or beta release.

Template	Effective value	Versus upstream boot	Source expression
OLTP	Unmodified	—	—
OLAP	Unmodified	—	—
CRIT	Unmodified	—	—
TINY	Unmodified	—	—

Caution

Advice — pending human review. Fact from the current Pigsty template projection: OLTP: PG9.4–19 Beta 3 unmodified; OLAP: PG9.4–19 Beta 3 unmodified; CRIT: PG9.4–19 Beta 3 unmodified; TINY: PG9.4–19 Beta 3 unmodified. No Pigsty-specific rationale is inferred from an absent override.

Common pitfalls

Changing session_preload_libraries in one session and assuming role defaults, database defaults, or other pooled sessions changed with it.
Naming a missing or ABI-incompatible module and causing connection failure or a server that cannot start.
Treating a search or preload path as harmless even though it defines which native code the server trusts.
Changing session_preload_libraries globally without a rollback plan and a client or operational compatibility test.

shared_preload_libraries · local_preload_libraries · dynamic_library_path · jit_provider · extension_control_path