Re: Constraint documentation

I have pushed this.

On 2018-Nov-26, David Fetter wrote:

> On Thu, Nov 22, 2018 at 03:16:11PM +0100, Patrick Francelle wrote:
>
> > To address your remark, I added a small message in the CREATE TABLE
> > reference page to be more explicit about the topic, so that it would be
> > a warning for the users reading the section. And then a reference to the
> > CHECK constraint page where the full explanation is to be located.
> > 
> > That way, the caveat is mentioned in both pages, but the full
> > explanation is located only on a single page.

That was a good idea, but your third sentence repeated what was being
said in the first sentence in the same paragraph.  I edited that to put
the cross-reference next to the first sentence instead.

> I believe that features F671 (subqueries in CHECK constraints) and
> possibly F673 (reads SQL-data routine invocations in CHECK
> constraints) from the standard should be referred to here.
> 
> We haven't implemented either one of them, but we might some day.

I don't necessarily disagree, but I don't think we put many feature
references in the docs.  I suppose we can edit it when we implement
F671 and F673.  Or maybe you want to submit a followup patch.  It didn't
seem worth blocking this patch for your proposed change (particularly
since Lætitia seems to have given up on it already).

Thanks,

-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
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