Re: Hook for extensible parsing.

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?