Re: Hook for extensible parsing.

From: Julien Rouhaud <rjuju123(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Simon Riggs <simon(dot)riggs(at)enterprisedb(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Jim Mlodgenski <jimmy76(at)gmail(dot)com>, PostgreSQL Developers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: Hook for extensible parsing.
Date: 2021-09-24 06:33:59
Message-ID: 20210924063359.csacjjszpzflnwlg@nol
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On Thu, Sep 23, 2021 at 10:21:20AM -0400, Tom Lane wrote:
> I do have sympathy for the idea that extensions would like to define
> their own statement types. I just don't see a practical way to do it
> in our existing parser infrastructure. This patch certainly doesn't
> offer that.

Allowing extensions to define their own (utility) statement type is just a
matter of allowing ExtensibleNode as top level statement. As far as I can
see the only change required for that is to give those a specific command tag
in CreateCommandTag(), since transformStmt() default to emitting a utility
command. You can then easily intercept such statement in the utility hook and
fetch your custom struct.

I could do that but I'm assuming that you still wouldn't be satisfied as
custom parser would still be needed, whihc may or may not require to
copy/paste chunks of the core grammar?

If so, do you have any suggestion for an approach you would accept?

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