>we need to ... understand SQL syntax using a parser, Rust ecosystem has a great library called pg_query

I'm impressed both that the Rust ecosystem had the right library available and that it was high enough quality code for the author's team to use it as a reference for building their own additional functionality.

Pgquery was created by the pganalyze team for their own purposes I believe initially for features like index recommendation tooling, but immediately planned as open source. It is indeed a very high quality project with the underlying C implementation having several wrappers that exist for a number of languages[1].

[1] https://github.com/pganalyze/libpg_query/blob/15-latest/READ...

Oddly, it actually originates from the Ruby ecosystem - `pganalyze` initially created `libpg_query` to parse Postgres in Ruby. `libpg_query` in C does the "magic" of reformulating Postgres's query parser into an AST generator, and serializes the resulting AST into a Protobuf. Then, `pg_query` bridges that into Rust.

We're using it to rewrite queries too. It's a pretty cool library.