Online VACUUM, REINDEX, and Table Rewrites
Bloat is the empty space dead rows leave behind.
You have two choices: let PostgreSQL reuse that space in place, which is cheap and stays online, or physically shrink the file to hand space back to the operating system, which is slower and can lock the table. Picking the heavy option at the wrong time turns a cleanup into an outage.
Pro members see the rest of this lesson
- A 4-step state diagram: Bloat → Vacuum → Rewrite → Repack
- The full mechanism: what PostgreSQL does internally, in source terms
- 2 SQL queries you can run, each labelled by how it was verified
- 1 transcript captured on PostgreSQL 17.10
- The closing insight, the mistake it prevents, and what it changes in your work
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Check it against the source3 citations in postgres/postgres · file, symbol and line verified on REL_17_STABLE
Primary symbol: heap_vacuum_rel · line 295
Primary symbol: cluster_rel · line 311
Primary symbol: DefineIndex · line 540
Anchored to postgres/postgres on REL_17_STABLE and cross-checked against the manual for PostgreSQL 15–18. Every query here was run and its output captured on a throwaway PostgreSQL 17.10 lab; corrections are noted inline. §25.1 Routine Reindexing in the official docs →
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