The thing rustc calls "queries" is more about incremental compilation- reusing work within and across compiler invocations, but without the sort of impact on memory layout and access patterns that you get from an RDBMS.
The closest thing I've seen in a compiler is rather Zig's AST memory layout work: https://github.com/ziglang/zig/pull/7920. But this is a very "hand-crafted" version of what an RDBMS does.
- https://nnethercote.github.io/2022/10/27/how-to-speed-up-the...
- https://nnethercote.github.io/2023/03/24/how-to-speed-up-the...
It's hard work. Small AST changes often require hundreds of changes to the code. The required changes usually make the AST less ergonomic to work with. And the perf benefits I obtained were very small. Even after shrinking `ast::Expr` (by far the most common AST node kind) from over 100 bytes to 64 bytes on 64-bit.
The linked Zig PR has very impressive reductions in walltime/cycles/etc. but if you read closely it's restricted just to parsing, which is usually a very small slice of compile time, at least for rustc. My experience with these kinds of changes was disappointing. I concluded "I’d love to be proven wrong, but it doesn’t feel like this work is taking place in a good part of the effort/benefit curve."
Their blog posts are also posted multiple times on Hacker News by different identities.
https://news.ycombinator.com/from?site=nnethercote.github.io
Seems odd that this wouldn’t go into an official Rust blog when you’re a member of the team and instead published on your personal domain and blog.
I started these posts back in 2016 when I wasn't a member of either. It's been a long-running series, and there's never been much reason for them to go on the official Rust blog, because they get enough attention on my personal blog.
In the past I have posted links to Hacker News but usually they don't make the front page and get few if any comments, so I stopped bothering, but others sometimes do. I always post to /r/rust where the level of discussion tends to be higher-quality than HN, because there is a higher level of Rust knowledge.