Peter Geoghegan

PostgreSQL 18 brought asynchronous I/O to most scan types, letting Postgres read ahead and hide storage latency instead of stalling on every page read. But support for "plain" index scans was deferred.

PostgreSQL 18 brought asynchronous I/O to most scan types, letting Postgres read ahead and hide storage latency instead of stalling on every page read. But support for "plain" index scans was deferred.

PostgreSQL's approach to MVCC is based on versioned storage, and owes much to the time travel feature that appeared in the original Berkeley codebase. An asynchronous cleanup process (VACUUM) garbage collects obsolete row versions, with additional cleanup performed by user transactions opportunistically.

Many PostgreSQL users have a basic understanding of how Postgres nbtree indexes work internally (e.g., how the structure is maintained, high level details of how a new level is added to the tree, the role of VACUUM in garbage collection). A smaller number have some understanding of advanced topics (e.g., details of Lehman & Yao's B-Link technique, details of crash recovery).