Re: Implement waiting for wal lsn replay: reloaded

Hi,

Thank you for the grammar review and the clear recommendation.

On Wed, Oct 15, 2025 at 4:51 PM Álvaro Herrera <alvherre(at)kurilemu(dot)de> wrote:
>
> I didn't review the patch other than look at the grammar, but I disagree
> with using opt_with in it. I think WITH should be a mandatory word, or
> just not be there at all. The current formulation lets you do one of:
>
> 1. WAIT FOR LSN '123/456' WITH (opt = val);
> 2. WAIT FOR LSN '123/456' (opt = val);
> 3. WAIT FOR LSN '123/456';
>
> and I don't see why you need two ways to specify an option list.

I agree with this as unnecessary choices are confusing.

>
> So one option is to remove opt_wait_with_clause and just use
> opt_utility_option_list, which would remove the WITH keyword from there
> (ie. only keep 2 and 3 from the above list). But I think that's worse:
> just look at the REPACK grammar[1], where we have to have additional
> productions for the optional parenthesized option list.
>
>
>
> So why not do just
>
> +opt_wait_with_clause:
> + WITH '(' utility_option_list ')' { $$ = $3; }
> + | /*EMPTY*/ { $$ = NIL; }
> + ;
>
> which keeps options 1 and 3 of the list above.

Your suggested approach of making WITH mandatory when options are
present looks better.
I've implemented the change as you recommended. Please see patch 3 in v16.

>
>
>
> Note: you don't need to worry about WITH_LA, because that's only going
> to show up when the user writes WITH TIME or WITH ORDINALITY (see
> parser.c), and that's a syntax error anyway.
>

Yeah, we require '(' immediately after WITH in our grammar, the
lookahead mechanism will keep it as regular WITH, and any attempt to
write "WITH TIME" or "WITH ORDINALITY" would be a syntax error anyway,
which is expected.

Best,
Xuneng