extra_float_digits

extra_float_digits is the PostgreSQL setting that defines the number of digits displayed for floating-point values.

Note

Fact — official short description: “Sets the number of digits displayed for floating-point values.”

Identity

Type , Valueinteger: Upstream pg_settings type
Context , Valueuser: Settable by an ordinary user
Unit , Value—: Raw unit
Range , Value-15 – 3: Raw limits in the last observed version
Enum values , Value—: — for non-enum types
Category , ValueClient Connection Defaults / Locale and Formatting: Upstream classification
Latest boot value , Value1: 1

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
PG9.0–11	`0`	—	0
PG12–19 Beta 3	`1`	—	1

How it works

extra_float_digits sets the number of digits displayed for floating-point values. This affects real, double precision, and geometric data types. A zero or negative parameter value is added to the standard number of digits (FLT_DIG or DBL_DIG as appropriate). Any value greater than zero selects precise output mode. Since PostgreSQL 12, positive values select shortest-precise output; zero and negative values request rounded legacy output and can lose round-trip fidelity.

extra_float_digits is a USER-context setting. An authorized role can change it for a session, while ALTER ROLE or ALTER DATABASE can establish a default for future sessions.

It changes representation, parsing, or locale behavior at the client boundary rather than physical storage. Coordinate it with the other locale and formatting settings and with driver-native binary or typed protocols.

Tuning advice

Tip

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

Workload	Guidance
OLTP	Treat extra_float_digits as an application contract, not a performance knob. Standardize it per role or connection pool and keep wire formats explicit where clients parse text.
OLAP	Pin extra_float_digits for export, reporting, and reproducible analytical jobs; prefer explicit SQL formatting when a file or API has a durable schema.
Small nodes	Keep the upstream or locale-derived value unless a client requires another one. A smaller server gains no capacity from changing extra_float_digits.

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: PG9.0–19 Beta 3 unmodified; OLAP: PG9.0–19 Beta 3 unmodified; CRIT: PG9.0–19 Beta 3 unmodified; TINY: PG9.0–19 Beta 3 unmodified. No Pigsty-specific rationale is inferred from an absent override.

Common pitfalls

Changing extra_float_digits in one session and assuming role defaults, database defaults, or other pooled sessions changed with it.
Assuming a presentation setting changes stored values or server-side type semantics.
Changing a role or database default without testing text-parsing clients, exports, and pooled sessions.
Carrying pre-12 assumptions forward even though positive values now select shortest-precise output.

bytea_output · xmlbinary · xmloption · client_encoding · DateStyle