Planner cost of a non-sequential page fetch.
At a glance
| Property | Value |
|---|---|
| Parameter | random_page_cost |
| Category | Query Planner |
| Default | 4.0 |
| Value type | boolean / enum / numeric |
| Change scope | Per-session (SET) |
What it does
The estimated cost of fetching a randomly-accessed disk page, relative to seq_page_cost (1.0). High values discourage index scans.
How to apply a change
Can be set per session with SET, per role/database with ALTER ROLE/DATABASE ... SET, or globally in postgresql.conf.
Inspect the current value and source with SHOW random_page_cost; or SELECT name, setting, unit, context, source FROM pg_settings WHERE name = 'random_page_cost';.
Tuning guidance
Lower to 1.1-1.5 on SSD/NVMe or well-cached databases — the default 4.0 assumes spinning disks and often wrongly favors sequential scans on modern storage.