Date: Tue, 13 Nov 2012 19:07:30 -0300
From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Noah Misch <noah@leadboat.com>
Cc: Simon Riggs <simon@2ndQuadrant.com>, Kevin Grittner <kgrittn@mail.com>,
	Andres Freund <andres@2ndquadrant.com>, pgsql-hackers@postgresql.org
Subject: Re: foreign key locks
Message-ID: <20121113220729.GA12811@alvh.no-ip.org>
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Noah Misch wrote:
> On Wed, Oct 31, 2012 at 05:22:10PM -0300, Alvaro Herrera wrote:

> > Not really sure about the proposed syntax, but yes clearly we need so=
me
> > other syntax to mean "FOR NON KEY UPDATE".  I would rather keep FOR
> > UPDATE to mean what I currently call FOR KEY UPDATE.  More proposals =
for
> > the other (weaker) lock level welcome (but if you love FOR NON KEY
> > UPDATE, please chime in too)
>=20
> Agree on having "FOR UPDATE" without any "FOR KEY UPDATE" synonym.  For=
 the
> weaker lock, I mildly preferred the proposal of "FOR NO KEY UPDATE".  N=
ON KEY
> captures the idea better in English, but NO is close enough and already=
 part
> of the SQL lexicon.

This is the proposal I like best; however there is an asymmetry, because
the locking options now are

FOR KEY SHARE
FOR SHARE
FOR NO KEY UPDATE
FOR UPDATE

I used to have comments such as

/* Currently, SELECT ... FOR [KEY] UPDATE/SHARE requires UPDATE privilege=
s */
#define ACL_SELECT_FOR_UPDATE	ACL_UPDATE

but now they are slightly incorrect because the NO is not illustrated.
I guess I could use SELECT ... FOR [NO KEY] UPDATE/SHARE but this leaves
out the "FOR KEY SHARE" case (and can be thought to introduce a FOR NO
KEY SHARE case).  And getting much more verbose than that is probably
not warranted.  In some places I would like the use a phrase like "the
locking clause", but I'm not sure that it's clear enough.

--=20
=C1lvaro Herrera                http://www.2ndQuadrant.com/
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