Fraction of table that must be dead before autovacuum runs.
At a glance
| Property | Value |
|---|---|
| Parameter | autovacuum_vacuum_scale_factor |
| Category | Autovacuum |
| Default | 0.2 |
| Value type | boolean / enum / numeric |
| Change scope | Reload (no restart) |
What it does
Autovacuum triggers when dead tuples exceed autovacuum_vacuum_threshold + scale_factor x reltuples. At 0.2 that is 20% of the table.
How to apply a change
Takes effect on configuration reload (sighup context). Run SELECT pg_reload_conf(); or send SIGHUP — no restart needed.
Inspect the current value and source with SHOW autovacuum_vacuum_scale_factor; or SELECT name, setting, unit, context, source FROM pg_settings WHERE name = 'autovacuum_vacuum_scale_factor';.
Tuning guidance
Lower per-table (e.g. 0.01-0.05) for large, frequently-updated tables — 20% of a 100M-row table is 20M dead tuples before cleanup, far too late. Set via ALTER TABLE ... SET (autovacuum_vacuum_scale_factor=...).