random_page_cost in Postgres - why the default is 4.0 and should you lower it? | POSETTE 2026

Name: random_page_cost in Postgres - why the default is 4.0 and should you lower it? | POSETTE 2026
Uploaded: 2026-06-16T20:50:57.000Z
Channel: Microsoft Developer

Postgresql Random_page_cost Postgresql tuning Query planner Database optimization Index scan Ssd performance Postgresql configuration Cost based optimizer Database performance

Microsoft Developer June 16, 2026

AI summary

PostgreSQL contributor Tomas Vondra explains the random_page_cost parameter, which controls the planner's estimate of random I/O cost relative to sequential reads. The talk explores why the default has been 4.0 since 2002, how modern SSDs have changed the I/O landscape, and provides practical guidance on whether to adjust this parameter for SSD workloads using real measurements with EXPLAIN ANALYZE.