maintenance_work_mem

The memory ceiling for maintenance commands such as VACUUM, CREATE INDEX, and adding foreign-key constraints.

Note

Fact — official short description: “Sets the maximum memory to be used for maintenance operations.”

Identity

Type , Valueinteger: Upstream pg_settings type
Context , Valueuser: Settable by an ordinary user
Unit , ValuekB: Raw unit
Range , Value64 – 2147483647: Raw limits in the last observed version
Enum values , Value—: — for non-enum types
Category , ValueResource Usage / Memory: Upstream classification
Latest boot value , Value65536: 64 MiB

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
PG9.0–9.3	`16384`	`kB`	16 MiB
PG9.4–19 Beta 3	`65536`	`kB`	64 MiB

How it works

maintenance_work_mem applies to maintenance operations including VACUUM, CREATE INDEX, and ALTER TABLE ADD FOREIGN KEY. Because a session normally runs only one such operation at a time, it can usually be set higher than work_mem.

For parallel utility commands, PostgreSQL treats maintenance_work_mem as a limit for the entire utility command rather than granting the full amount to every parallel maintenance worker. CPU and I/O consumption can still rise with parallelism.

Autovacuum is a separate concurrency concern: when autovacuum_work_mem is -1, each autovacuum worker inherits maintenance_work_mem, so several workers can make the aggregate budget much larger than the single-operation value.

Tuning advice

Tip

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

Workload	Guidance
OLTP	Use enough memory to keep routine vacuum and index work efficient, but budget explicitly for simultaneous autovacuum workers. If interactive latency matters and maintenance_work_mem is large, give autovacuum_work_mem its own lower ceiling.
OLAP	Larger values are often useful for index builds, vacuuming large relations, and restores. Schedule heavy maintenance and verify that concurrent maintenance, query memory, and the OS still fit together.
Small nodes	Keep the global value modest and temporarily raise it only for controlled maintenance sessions. Check autovacuum inheritance before increasing it.

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	`2048MB`	different	`{{ pg_maintenance_mem }}MB`
OLAP	`4096MB`	different	`{{ pg_maintenance_mem }}MB`
CRIT	`2048MB`	different	`{{ pg_maintenance_mem }}MB`
TINY	`2048MB`	different	`{{ pg_maintenance_mem }}MB`

Caution

Advice — pending human review. Fact from the current Pigsty template projection: OLTP: PG9.0–19 Beta 3 = 2048MB (dcs); OLAP: PG9.0–19 Beta 3 = 4096MB (dcs); CRIT: PG9.0–19 Beta 3 = 2048MB (dcs); TINY: PG9.0–19 Beta 3 = 2048MB (dcs). Advice, pending human review — Editorial inference: the larger OLAP fraction is intended to favor bulk maintenance, while inherited autovacuum exposure needs separate review.

Common pitfalls

Assuming the value is harmless because maintenance is infrequent while leaving autovacuum_work_mem at -1.
Multiplying the limit by parallel maintenance workers; PostgreSQL applies it to the utility command as a whole.
Using a permanently large cluster-wide value for a one-off restore instead of a scoped SET.
Expecting more memory alone to solve maintenance dominated by locks or storage I/O.

autovacuum_work_mem · autovacuum_max_workers · max_parallel_maintenance_workers · vacuum_buffer_usage_limit · work_mem