Re: Small docs bugfix: make it clear what can be used in UPDATE FROM and DELETE USING

On Thu, Feb 13, 2020 at 11:26:45AM -0500, Tom Lane wrote:
> I see where you're coming from, but I do not think that repeating the
> whole from_item syntax in UPDATE and DELETE is the best way forward.
> In the first place, we'd inevitably forget to update those copies,
> and in the second, I'm not sure that the syntax is all that helpful
> without all the supporting text in the SELECT ref page --- which
> surely we aren't going to duplicate.
>
> I think the real problem with the places Alexey is on about is that
> they're too waffle-y. They use wording like "similar to", leaving
> one wondering what discrepancies exist but are being papered over.
> In point of fact, as a look into gram.y will show, what you can
> write after UPDATE ... FROM or DELETE ... USING is *exactly* the
> same thing as what you can write after SELECT ... FROM. So what
> I'm in favor of here is:
>
> * Change the synopsis entries to look like "FROM from_item [, ...]"
> and "USING from_item [, ...]", so that they match the SELECT
> synopsis exactly.
>
> * In the text, describe from_item as being exactly the same as
> it is in SELECT.
>
> (Compare the handling of with_query, which has pretty much the
> same problem of being way too complex to document three times.)

I have implemented the ideas above in the attached patch. I have
synchronized the syntax to match SELECT, and synchronized the paragraphs
describing the item.

--
Bruce Momjian <bruce(at)momjian(dot)us> https://momjian.us
EnterpriseDB https://enterprisedb.com

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