vacuum_multixact_freeze_table_age

vacuum_multixact_freeze_table_age — Multixact age at which VACUUM should scan whole table to freeze tuples. Observed in PG9.3–19 Beta 3; its last measured boot default is 150000000 in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.

Note

Fact — official short description: “Multixact age at which VACUUM should scan whole table to freeze tuples.”

Identity

Type , Valueinteger: Upstream pg_settings type
Context , Valueuser: Settable by an ordinary user
Unit , Value—: Raw unit
Range , Value0 – 2000000000: Raw limits in the last observed version
Enum values , Value—: — for non-enum types
Category , ValueVacuuming / Freezing: Upstream classification
Latest boot value , Value150000000: 150000000

Lifecycle

Fact	Value
First observed	PG9.3
Present in	PG9.3–19 Beta 3
Removed in	No
Introduction commit	`fb47de2be6e4` — Separate multixact freezing parameters from xid’s
Commit date	2014-02-13
Discussion	—

Default history

Measured PG9.0–19 Beta 3 boot defaults
Versions	Raw `boot_val`	Unit	Human value
PG9.3–19 Beta 3	`150000000`	—	150000000

How it works

Sets the MultiXact age at which VACUUM switches to an aggressive scan so it can advance a table’s relminmxid. It is a user-context setting.

An aggressive MXID scan visits every page not already all-frozen and processes eligible MultiXacts. PostgreSQL caps the effective value at 95% of autovacuum_multixact_freeze_max_age.

Monitor mxid_age(relminmxid), mxid_age(datminmxid), and pg_multixact storage. The XID horizon relfrozenxid is controlled by vacuum_freeze_table_age instead.

Tuning advice

Tip

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

Workload	Guidance
OLTP	Choose an MXID threshold that leaves enough time to complete aggressive scans before autovacuum_multixact_freeze_max_age. Measure workloads with heavy shared row locking.
OLAP	Most read-only analytics consume few MXIDs, but concurrent loaders can differ. Schedule scans from measured mxid_age and member-space growth rather than copying XID settings.
Small nodes	Keep the default and monitor relminmxid/datminmxid. A small database can still consume MXIDs rapidly through row-locking patterns.

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

Common pitfalls

Monitoring relfrozenxid instead of the MultiXact horizon relminmxid.
Using autovacuum_freeze_max_age rather than autovacuum_multixact_freeze_max_age for the 95% cap.
Copying an XID-age policy into an MXID workload with a very different consumption rate.
Ignoring pg_multixact member-space pressure while age still appears comfortable.

autovacuum_multixact_freeze_max_age · vacuum_multixact_freeze_min_age · vacuum_multixact_failsafe_age · vacuum_freeze_table_age · autovacuum · log_autovacuum_min_duration