zlacker

> The section on multi-column indexes mirrors how I was taught and how I’ve generally handled such indexes in the past. But is it still true for more recent PG versions?

No, it isn't. PostgreSQL 18 added support for index skip scan:

https://youtu.be/RTXeA5svapg?si=_6q3mj1sJL8oLEWC&t=1366

It's actually possible to use a multicolumn index with a query that only has operators on its lower-order columns in earlier versions. But that requires a full index scan, which is usually very inefficient.

>>peterg+(OP)
Hi Peter, author here. Thanks for weighing in with the extra context on index skip scan, and huge thanks for adding this to Postgres.

I’m going to revise the multi-column index section to be more precise about when leftmost-prefix rules apply, and I’ll include a note on how skip scan changes the picture