lc_collate

lc_collate — Shows the collation order locale. Observed in PG9.0–15; its last measured boot default is C in PG15, with internal context. It was removed in PG16.

Note

Fact — official short description: “Shows the collation order locale.”

Identity

Type , Valuestring: Upstream pg_settings type
Context , Valueinternal: Internal/preset and not user-settable
Unit , Value—: Raw unit
Range , Value—: Raw limits in the last observed version
Enum values , Value—: — for non-enum types
Category , ValuePreset Options: Upstream classification
Latest boot value , ValueC: C

Lifecycle

Fact	Value
First observed	PG9.0 (research boundary)
Present in	PG9.0–15
Removed in	PG16
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
PG9.0–15	`C`	—	C

How it works

Reported the current database’s collation locale through PG15. It was an internal read-only value, not a configurable GUC, and PostgreSQL 16 removed it from pg_settings.

The collation locale is selected when a database is created and can differ between databases in one cluster. It affects ordering and comparison semantics; changing the server configuration cannot rewrite existing indexes or database locale metadata.

On PG16 and later, monitoring and applications should read the current database row in pg_database and its locale-provider-specific metadata, and use pg_collation for individual collation objects. Test collation-version changes separately from this removed reporter.

Tuning advice

Tip

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

Workload	Guidance
OLTP	Not tunable. Replace SHOW/current_setting readers with a version-aware pg_database query, and regression-test indexed ordering and uniqueness when moving databases between locale providers or versions.
OLAP	Record per-database provider and locale beside analytical exports. A desired collation change requires a deliberate database/object migration and possible REINDEX, not a GUC edit.
Small nodes	Use the database-creation default only when it is intentional. Preserve locale metadata in inventory and backups so a rebuild does not silently choose different ordering rules.

Pigsty

Values use the fixed 8-vCPU, 32-GiB, 100-GiB SSD fixture and render the current Pigsty templates for PG15; 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: PG9.0–15 unmodified; OLAP: PG9.0–15 unmodified; CRIT: PG9.0–15 unmodified; TINY: PG9.0–15 unmodified. No Pigsty-specific rationale is inferred from an absent override.

Common pitfalls

Trying to remove or set lc_collate in configuration even though it was always internal/read-only.
Assuming one cluster-wide value applies to every database.
Changing operating-system or ICU locale data without checking collation versions and rebuilding affected indexes.
Comparing text behavior across providers using only a locale name.

lc_ctype · server_encoding · client_encoding · icu_validation_level · default_text_search_config · server_version_num