From: | Bruce Momjian <bruce(at)momjian(dot)us> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com>, Alexey Bashtanov <bashtanov(at)imap(dot)cc>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Small docs bugfix: make it clear what can be used in UPDATE FROM and DELETE USING |
Date: | 2020-03-18 00:31:43 |
Message-ID: | 20200318003143.GD17915@momjian.us |
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Lists: | pgsql-hackers |
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
+ As you are, so once was I. As I am, so you will be. +
+ Ancient Roman grave inscription +
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