libpg_query

Yeah, as one of the main authors of libpg_query, I think the primary things that make this easier is that Postgres has good abstractions internally, and the parser works independently from other parts (e.g. the community discourages adding settings that affect parser behavior). Over the years we've only had to maintain a small set of patches on top of the Postgres source [0], together with some mocks and our libclang-based extraction logic [1]. Of course it would be nice if Postgres just packaged this directly like it packages the client libraries, but there is non-trivial effort involved to do that. From what I recall, the main issue is that error handling and memory allocations work differently in the client-side libraries (and so that would have to either also be moved out of the backend source, or use some other abstraction). [0]: htt

Yes, the same way. It's all based on the extremely useful `https://github.com/pganalyze/libpg_query` project, which is where the "extracted the parser from Postgres" part comes in. Supabase's LSP also uses tree-sitter for corrections and autocomplete, because one drawback of using the server's source is that pg_query only works on well-formed/executable SQL - when it detects a malformed query, it formulates an error and exits, since that's what you want in an SQL server. So for partially-correct syntax and fill-forward, tree-sitter covers the gaps.

Tends to be a matter of opinion. Postgres does not expose the relevant functions, so https://github.com/pganalyze/libpg_query has to do some heavy lifting to convert their source code into a nice library. Conversely, Postgres is very well written code, in an extremely common language, with a stable release cadence, and such a long track record it is seen as the reference implementation for correctly parsing SQL.

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...