Page Layout: How PostgreSQL Stores Rows on Disk
PostgreSQL stores a table as a stack of fixed-size pages, 8KB each, and rows live inside those pages.
Once a file of pages grows to 1GB, the database starts another file. Knowing this layout is the key to understanding where a row actually sits on disk.
Pro members see the rest of this lesson
- A 4-step state diagram: Empty → Insert → Fill → Full
- The full mechanism: what PostgreSQL does internally, in source terms
- 1 SQL query 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 source1 citation in postgres/postgres · file, symbol and line verified on REL_17_STABLE
Primary symbol: PageHeaderData · line 155
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. §73.6 Database Page Layout in the official docs →
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