Date: Fri, 15 Sep 2006 17:20:53 -0400
From: Alvaro Herrera <alvherre@commandprompt.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-docs@postgreSQL.org, Joe Conway <mail@joeconway.com>
Subject: Re: Proposal for documenting 8.2 VALUES syntax
Message-ID: <20060915212052.GB17919@alvh.no-ip.org>
Mail-Followup-To: Tom Lane <tgl@sss.pgh.pa.us>, pgsql-docs@postgreSQL.org,
	Joe Conway <mail@joeconway.com>
References: <6015.1158354891@sss.pgh.pa.us>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <6015.1158354891@sss.pgh.pa.us>
User-Agent: Mutt/1.5.13 (2006-08-11)

Tom Lane wrote:
> I spent a bit of time thinking about the best way to document 8.2's more
> powerful VALUES clause.  Here's the plan I came up with:
> 
> * There needs to be some introductory material in Part II, and the only
> place it seems to fit at all is under Chapter 7, Queries.  I think there
> should be a new <sect1> page covering VALUES.  We could add it at the
> end of the chapter (ie, a new section 7.7) or we could insert it between
> sections 7.3 Select Lists and 7.4 Combining Queries.  The argument for
> the latter position is that VALUES is now syntactically parallel to
> SELECT, and so you can use it as if it were SELECT in UNION/INTERSECT/
> EXCEPT structures as described in 7.4, as well as attach the ORDER BY,
> LIMIT, OFFSET clauses described in 7.5 and 7.6.  However that might be
> putting too much emphasis on syntactic form as opposed to pedagogical
> clarity.  I'm a bit inclined to put it at the end of the chapter and
> then explain "by the way, you can also attach that other stuff to it".
> Thoughts?

I agree with putting it at the end of the chapter.

> * The SELECT reference page is huge already, so I would rather add only
> the minimum possible amount to it.  This leads to the conclusion that
> we'd better create a new ref/ entry just for VALUES.  I think that's
> appropriate anyway, since there is some material that doesn't seem like
> it would fit anywhere else --- in particular, that we want to warn off
> people from expecting umpteen-billion-row VALUES constructs to work
> well.

I agree here as well.  One likely useful example, if not already
covered, is

select ... FROM ... WHERE op ANY (VALUES ( ... ))

I tripped over it a couple of days ago and it seems useful and non
obvious.  ISTM it beats the current practice of 

op ANY(ARRAY[ ... ])

which seems a bit of a kludge.

-- 
Alvaro Herrera                                http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support