| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | rir <rirans(at)comcast(dot)net> |
| Cc: | Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at>, pgsql-docs(at)lists(dot)postgresql(dot)org |
| Subject: | Re: small patch |
| Date: | 2021-10-07 20:24:16 |
| Message-ID: | 175281.1633638256@sss.pgh.pa.us |
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| Lists: | pgsql-docs |
rir <rirans(at)comcast(dot)net> writes:
> On Thu, Oct 07, 2021 at 07:58:47AM +0200, Laurenz Albe wrote:
>> Can you think of a way to modify the syntax diagram so that it
>> expresses that and still remains comprehensible?
> For myself,
> 'FETCH [ <direction> [ FROM | IN ] ] <cursor_name>'
> clearly indicates that 'direction' is optional.
Right, but if we don't say that <direction> can be
empty, then this diagram disallows
FETCH FROM cursor_name
which in fact is legal. I think however that we could make it read
FETCH [ <direction> ] [ FROM | IN ] <cursor_name>'
and have a correct description without requiring <direction>
to be allowed to be empty.
BTW, as it stands, the diagram is ambiguous
because there are two ways to parse
FETCH cursor_name
... is <direction> present but empty, or omitted altogether?
regards, tom lane
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