Subject: <from_item> doc has self referential definition

From: PG Doc comments form <[email-masked]>
Date: Thu, 04 Jan 2018 02:58:08 +0000

The following documentation comment has been logged on the website:

Page: https://www.postgresql.org/docs/9.5/static/sql-select.html
Description:

https://www.postgresql.org/docs/9.6/static/sql-select.html

The last line for <from_item> breaks the group.  There should be something
like:

<from_item>
   <join_from>
   <simple_from>

(with better naming).

Thanks for Postgresql.

Rob

---

From: Tom Lane <[email-masked]>
Date: Wed, 03 Jan 2018 22:33:39 -0500

> (with better naming).

Hm, I can't get excited about it.  You're correct that the grammar
as stated is ambiguous, and if we introduced another level of
nonterminal we could make it reflect the left-to-right precedence
of join operators ... but I think 99% of our users would just find
it more confusing that way.  The existing statement in the text that
"In the absence of parentheses, JOINs nest left-to-right" is probably
clearer to most people than a formal grammar for it would be.

(Heck, even our actual bison grammar file relies on precedence to
define this behavior, rather than an extra nonterminal ... and you
can't get much nerdier than a bison grammar.)

			regards, tom lane