PostgreSQL 18: async I/O, uuidv7, and an upgrade path that hurts less

PostgreSQL 18 was released on September 25, 2025. The headline trio is asynchronous I/O, a smoother upgrade experience, and developer features. In day-to-day operations that means: faster reads, less painful major upgrades, and a few things that used to require extensions now in core.

Three reasons to upgrade

One: the async I/O subsystem. Historically a PostgreSQL backend issued a read and waited. 18 adds a pluggable AIO layer (io_method can be worker or io_uring), with the project measuring up to 3x improvements when reading from storage. Mind the “up to”: sequential scans and read-ahead-heavy workloads benefit most, while in-memory or tiny-transaction OLTP gains are modest.

Two: uuidv7() in core. A v7 UUID puts the timestamp in the high bits, which gives much better index locality. Previously you needed an extension or application-side generation; now SELECT uuidv7(); works. For tables that use UUID primary keys and suffer on insert performance, this is the cheapest fix available.

Three: upgrades hurt less. pg_upgrade now preserves optimizer statistics, so you do not need a full ANALYZE round to get back to the old plans. Parallel checks and incremental backup also improved.

Also worth knowing

• Virtual generated columns: computed at query time, no storage cost — handy for indexing a field pulled out of JSON;
• OAuth 2.0 authentication: connect directly to an identity provider instead of putting a proxy in front;
• Skip scan: multi-column B-tree indexes become usable even when the leading column has low cardinality;
• EXPLAIN improvements: more information, less guessing.

The upgrade path

1. Run pg_upgrade --check against a replica or shadow cluster first, and pay attention to extension compatibility (pgvector, PostGIS and friends);
2. Leave io_method at its default, benchmark, then decide whether io_uring is worth it;
3. Check connection poolers and driver versions. The protocol did not change much, but driver support for OAuth and the newer auth methods varies;
4. After the major upgrade, re-check the plans of your critical queries to make sure nothing regressed through statistics or planner changes.

The judgement

PostgreSQL 18 is not a feature-explosion release. It fixes the foundations: modern I/O, smoother upgrades, better UUIDs. If your database already shows read I/O pressure, this may be the most worthwhile major upgrade in years.

Cover image: PostgreSQL press kit (postgresql.org).