Date: Wed, 20 May 2015 20:26:17 +0200
From: Andres Freund <andres@anarazel.de>
To: Peter Geoghegan <pg@heroku.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Thom Brown <thom@linux.com>,
 hlinnaka <hlinnaka@iki.fi>, Jeff Janes <jeff.janes@gmail.com>,
 Stephen Frost <sfrost@snowman.net>,
 Dean Rasheed <dean.a.rasheed@gmail.com>, Bruce Momjian <bruce@momjian.us>,
 Pg Hackers <pgsql-hackers@postgresql.org>
Subject: Re: INSERT ... ON CONFLICT UPDATE/IGNORE 4.0
Message-ID: <20150520182617.GA10047@alap3.anarazel.de>
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On 2015-05-20 11:24:06 -0700, Peter Geoghegan wrote:
> On Wed, May 20, 2015 at 10:37 AM, Andres Freund <andres@anarazel.de> wrote:
> > But you *can* use a exclusion constraint for DO NOTHING. Just not (yet)
> > for DO UPDATE.
> 
> FWIW, I don't think exclusion constraint DO UPDATE support is ever
> going to be useful.

Why?

Even if maybe not directly under the guise of exclusion constraints
themselves, but I do think it's an interesting way to more easily allow
to implement unique constraints on !amcanunique type indexes.  Or, more
interestingly, for unique keys spanning partitions.


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