Switch query parser to `pg_query.rs`

[mdashti]

Is your feature request related to a problem? Please describe.
Currently, pgcat is using sqlparser-rs to parse user queries. That's taken us to where we are today, which is great. However, sqlparser-rs does not correctly parse all PostgreSQL queries. There are already some open PRs to fix the known issues (e.g., apache/datafusion-sqlparser-rs#1000 and apache/datafusion-sqlparser-rs#1002), but it's not going to be 100% PG compatible.

Describe the solution you'd like
The closest to PostgreSQL parser that we can get is to use the PostgreSQL parser itself :)

Here's the maintained (extracted) C library: libpg_query, and here's its port to Rust (by pganalyze): pg_query.rs

I wanted to ask for everyone's opinion (especially the main pgcat maintainers) about changing our SQL parser from sqlparser-rs to pg_query.rs. If I see enough support for this change, I can put-together a PR for it.

[levkk]

I believe not only pg_query.rs is the most correct Postgres SQL parser but also it's faster than sqlparser. There is a draft PR by another contributor with that integration: #525

[mdashti]

Thanks for the reference to PR #525. Cool stuff!

However, that PR only uses pg_query.rs without removing the current usages of sqlparser. I'll create a PR for that.

[KennyChenFight]

Just curious about any progress for this ?