shared_preload_libraries

shared_preload_libraries is the PostgreSQL setting that lists shared libraries to preload into server.

Note

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

Identity

Type , Valuestring: Upstream pg_settings type
Context , Valuepostmaster: Requires a server restart
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	PG9.0 (research boundary)
Present in	PG9.0–19 Beta 3
Removed in	No
Introduction commit	Not asserted: predates the PG9.0 research boundary
Commit date	—
Discussion	—

Default history

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

How it works

shared_preload_libraries lists shared libraries to preload into server. Libraries load once in the postmaster before shared memory is finalized, enabling hooks and shared state unavailable to later LOAD; one missing library prevents server startup.

shared_preload_libraries is a POSTMASTER-context setting: PostgreSQL reads it during server startup, and a configuration reload or session SET cannot activate a new value.

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 shared_preload_libraries generically. Load or expose only modules required by a reviewed feature, verify binary compatibility, and rehearse failure recovery before rollout.
OLAP	Use shared_preload_libraries for a measured extension or JIT requirement, accounting for backend startup, resident memory, and behavior under connection pooling.
Small nodes	Keep shared_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	`pg_stat_statements, auto_explain`	different	`'{{ pg_libs \| default("pg_stat_statements, auto_explain") }}'`
OLAP	`pg_stat_statements, auto_explain`	different	`'{{ pg_libs \| default("pg_stat_statements, auto_explain") }}'`
CRIT	`pg_stat_statements, auto_explain`	different	`'{{ pg_libs \| default("$libdir/passwordcheck, pg_stat_statements, auto_explain") }}'`
TINY	`pg_stat_statements, auto_explain`	different	`'{{ pg_libs \| default("pg_stat_statements, auto_explain") }}'`

Caution

Advice — pending human review. Fact from the current Pigsty template projection: OLTP: PG9.0–19 Beta 3 = pg_stat_statements, auto_explain (dcs); OLAP: PG9.0–19 Beta 3 = pg_stat_statements, auto_explain (dcs); CRIT: PG9.0–19 Beta 3 = pg_stat_statements, auto_explain (dcs); TINY: PG9.0–19 Beta 3 = pg_stat_statements, auto_explain (dcs). Advice, pending human review — Editorial inference: pg_stat_statements and auto_explain provide fleet-wide query statistics and targeted slow-plan evidence, accepting restart-time loading and shared overhead.

Common pitfalls

Expecting a reload or SET to activate shared_preload_libraries, although it requires a controlled server restart.
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 shared_preload_libraries globally without a rollback plan and a client or operational compatibility test.

session_preload_libraries · local_preload_libraries · dynamic_library_path · jit_provider · extension_control_path