Vacuum at the Page Level
This technical article explores the internal mechanics of PostgreSQL's VACUUM process, specifically focusing on how it cleans up dead tuple space. It provides a deep dive into page headers and visibility maps using diagnostic tools.
Why it matters
Understanding database maintenance is critical for engineers optimizing performance and storage in large-scale PostgreSQL deployments.
In HOT Updates in Postgres we covered page pruning clean up HOT chains, an elegant shortcut where PostgreSQL reclaims dead tuple space during ordinary reads. All that without waiting for any background process. But pruning is exactly that: a shortcut. It only works within a single page, and only for HOT-updated tuples. For everything else (cold updates that touch indexed columns, plain DELETEs, index entry cleanup, free space map registration, visibility map maintenance) we need VACUUM.
Purely technical documentation and tutorial content.
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