TLDR Tech / Practical
PostgreSQL 18 async I/O dramatically reduces vacuum time on disk reads
The new asynchronous I/O system in PostgreSQL 18, which uses three worker processes by default, has shown significant improvements for disk-intensive operations. While performance for cached queries remains unchanged, uncached tasks like sequential scans, bitmap heap scans, and full table vacuums are now considerably faster. The analysis also covers the effects of altering the io_workers and effective_io_concurrency parameters.
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