🔍PostgreSQL Random_Page_Cost Defaults Under Scrutiny
PostgreSQL's random_page_cost is getting a rethink
TL;DR
PostgreSQL's random_page_cost defaults are being questioned, with the default of 4.0 not accurately reflecting real-world I/O costs. This impacts query planning and performance tuning.
PostgreSQL's default random_page_cost of 4.0 is being reevaluated, as it doesn't accurately represent the cost of random I/O on modern storage. This impacts query planning and performance tuning, pushing the planner towards inefficient plans. The estimated random_page_cost for SATA drives is 125, compared to 2-4 times less for SSDs. This change affects how developers tune their PostgreSQL databases for optimal performance. The cost model ignores memory and has a safety limit called work_mem, which limits work buffer sizes. Tuning must be system-specific and driven by monitoring feedback.
Key Points
Default random_page_cost is 4.0, but SATA drives cost 125, SSDs 2-4 times less.
Increasing random_page_cost doesn't improve performance, it hurts it.
Cost model ignores memory and has a safety limit called work_mem.
Sequential scans push data from memory, while index scans access less data.
Tuning random_page_cost must be system-specific and driven by monitoring.
Why It Matters
If you're tuning PostgreSQL for performance, the default random_page_cost of 4.0 is misleading. SATA drives cost 125, SSDs 2-4 times less. This impacts query planning and performance tuning, pushing the planner towards inefficient plans. Developers must tune random_page_cost system-specifically based on monitoring feedback.
Frequently Asked Questions
Why does this matter?
If you're tuning PostgreSQL for performance, the default random_page_cost of 4.0 is misleading. SATA drives cost 125, SSDs 2-4 times less. This impacts query planning and performance tuning, pushing the planner towards inefficient plans. Developers must tune random_page_cost system-specifically based on monitoring feedback.
What happened?
PostgreSQL's random_page_cost defaults are being questioned, with the default of 4.0 not accurately reflecting real-world I/O costs. This impacts query planning and performance tuning.
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