Vol. I · A Postgres Handbook

The Query & the Schema

A reading-room reference for writing PostgreSQL by hand — selects to window functions, with the schema in plain view.

AdvancedAdvanced PostgreSQL

Theory: Fillfactor

The query

SQL
-- Q: What is FILLFACTOR?
-- A: A table storage parameter (10 to 100). Default is 100%.
-- If set to 90, PostgreSQL leaves 10% of every disk page empty. 
-- When a row is updated, PostgreSQL can place the new MVCC version of the row 
-- on the SAME page (Heap-Only Tuples - HOT update), dramatically saving index IO.
Tested against PostgreSQL 16

Note

“Lower fillfactor is highly recommended for tables that experience massive amounts of UPDATEs.