autovacuum_vacuum_scale_factor

Autovacuum vacuums a table once the number of dead rows exceeds autovacuum_vacuum_threshold + autovacuum_vacuum_scale_factor × table size. The default scale factor of 0.2 means a table waits until ~20% of it is dead before being vacuumed.

20% is far too much churn to tolerate on a large, hot table — it bloats badly before vacuum runs. Lower it per-table for big tables (e.g. 0.01–0.05 via ALTER TABLE … SET) so vacuum runs on a smaller, more frequent slice. Small tables are fine at the default.

• Index Only Scan

Why does my big table bloat even with autovacuum on?

The default 0.2 scale factor lets 20% of a huge table become dead rows before autovacuum touches it. Lower autovacuum_vacuum_scale_factor for that table (e.g. 0.02) so it's vacuumed in smaller, more frequent passes.

• autovacuum_analyze_scale_factor
• autovacuum_vacuum_insert_scale_factor
• autovacuum_vacuum_cost_limit