Re: [PATCH] Add --syntax to postgres for SQL syntax checking

ne 25. 2. 2024 v 23:24 odesílatel Tomas Vondra
<tomas.vondra@enterprisedb.com> napsal:
>
>
>
> On 12/15/23 16:38, Josef Šimánek wrote:
> > pá 15. 12. 2023 v 16:32 odesílatel David G. Johnston
> > <david.g.johnston@gmail.com> napsal:
> >>
> >> On Fri, Dec 15, 2023 at 8:20 AM Josef Šimánek <josef.simanek@gmail.com> wrote:
> >>>
> >>> (parser is not available
> >>> in public APIs of postgres_fe.h or libpq).
> >>
> >>
> >> What about building "libpg" that does expose and exports some public APIs for the parser?  We can include a
referenceCLI implementation for basic usage of the functionality while leaving the actual language server project
outsideof core. 
> >
> > Language server (LSP) can just benefit from this feature, but it
> > doesn't cover all possibilities since LSP is meant for one purpose ->
> > run in developer's code editor. Actual syntax check is more generic,
> > able to cover CI checks and more. I would not couple this feature and
> > LSP, LSP can just benefit from it (and it is usually built in a way
> > that uses other tools and packs them into LSP). Exposing this kind of
> > SQL check doesn't mean something LSP related being implemented in
> > core. LSP can just benefit from this.
> >
>
> I don't know enough about LSP to have a good idea how to implement this
> for PG, but my assumption would be we'd have some sort of library
> exposing "parser" to frontend tools, and also an in-core binary using
> that library (say, src/bin/pg_syntax_check). And LSP would use that
> parser library too ...
>
> I think there's about 0% chance we'd add this to "postgres" binary.

Exposing parser to frontend tools makes no sense to me and even if it
would, it is a huge project not worth to be done just because of
syntax check. I can update the patch to prepare a new binary, but
still on the backend side. This syntax check should be equivalent to
running a server locally, running a query and caring only about
parsing part finished successfully. In my thinking, this belongs to
backend tools.

> > Exposing parser to libpg seems good idea, but I'm not sure how simple
> > that could  be done since during my journey I have found out there are
> > a lot of dependencies which are not present in usual frontend code per
> > my understanding like memory contexts and removal of those
> > (decoupling) would be huge project IMHO.
> >
>
> You're right the grammar/parser expects a lot of backend infrastructure,
> so making it available to frontend is going to be challenging. But I
> doubt there's a better way than starting with gram.y and either removing
> or adding the missing pieces (maybe only a mock version of it).
>
> I'm not a bison expert, but considering your goal seems to be a basic
> syntax check, maybe you could simply rip out most of the bits depending
> on backend stuff, or maybe replace them with some trivial no-op code?
>
> But as Tom mentioned, the question is how far gram.y gets you. There's
> plenty of ereport(ERROR) calls in src/backend/parser/*.c our users might
> easily consider as parse errors ...
>
>
> regards
>
> --
> Tomas Vondra
> EnterpriseDB: http://www.enterprisedb.com
> The Enterprise PostgreSQL Company