What is fillfactor and how does it affect PostgreSQL performance?

PostgreSQL Fillfactor: A Quick Clarification

Fillfactor works much like in other relational databases. However, there's a key nuance: PostgreSQL only preserves the designated empty space after a table rebuild or vacuum cycle. As regular DML operations proceed, pages gradually fill up again, and the benefit diminishes until the next vacuum runs.

Why It Matters for Performance

The offset is important for tuning write-heavy workloads, as properly set fillfactor can reduce page splits and keep HOT (Heap-Only Tuple) updates efficient. But the effect is temporary between maintenance events.