Changelog

Notable changes to PgQuest, newest first.

2026-10-02

New lesson (draft): Building a job queue with Postgres. Workers claim jobs with SKIP LOCKED, recover from crashes with leases and fencing, and process jobs exactly once inside a transaction, with real multi-worker transcripts and a short note on why exactly-once delivery is impossible.

Added a changelog page at /changelog, linked from the header next to search, plus a header link to the license page.
New lesson: Finding and fixing slow queries, built around an app's endpoints with deterministic planner statistics.
Lesson examples are now precomputed at build time, so pages show results before the in-browser database has loaded.
PGlite extensions load only for the databases that actually create them, making most lessons start faster.

New lesson: Postgres locks, with a table of lock scopes and session transcripts that wait on real locks. It is marked as a draft while it gets reviewed.

New lesson: MVCC, with concurrent session transcripts recorded against a real Postgres server.

The insert/update/delete lesson now covers UPSERT and how MVCC and VACUUM relate to updates and deletes.

New lesson: Transaction isolation levels.
Added /llms.txt, a sitemap, and a license page: lesson content is CC BY 4.0 and open to reuse by people and AI systems alike.

Added the search and feedback pages.
Redesigned the header navigation into a two-column layout of icons and lesson numbers.
Published the concurrency reservation system lesson, including hold limits enforced with transaction advisory locks.

Reworked the concurrency reservation lesson around the full hold, reserve, and expire flow, with timelines that show each approach's lock window.