Date: Tue, 31 Oct 2006 16:22:53 -0500
From: Andrew Sullivan <ajs@crankycanuck.ca>
To: pgsql-sql@postgresql.org
Subject: Re: record datatype comparisons
Message-ID: <20061031212253.GD20809@phlogiston.dyndns.org>
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On Tue, Oct 31, 2006 at 12:38:36PM -0800, George Pavlov wrote:
> Both (1::int,'a'::varchar) and (select (2::int,'a'::varchar)) are of
> type record, aren't they?

I don't think so.  Psql gives you a hint that not:

testing=# SELECT (1::int, 'a'::varchar);
  row  
-------
 (1,a)
(1 row)

testing=# SELECT (SELECT(1::int, 'a'::varchar));
 ?column? 
----------
 (1,a)
(1 row)

Note the column headers.  They're differently shaped.  Because
pseudotype record doesn't have a shape, equality doesn't make sense,
so you need two shapes that are already identical, so they can use
the matching rules for that.

A

-- 
Andrew Sullivan  | ajs@crankycanuck.ca
Everything that happens in the world happens at some place.
		--Jane Jacobs