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Re: strange IS NULL behaviour

Bruce Momjian <bruce@momjian.us>

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From: Bruce Momjian <bruce@momjian.us>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Hannu Krosing <hannu@2ndQuadrant.com>, Peter Eisentraut <peter_e@gmx.net>, Andrew Dunstan <andrew@dunslane.net>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2013-09-04T02:54:15Z
Lists: pgsql-hackers 
On Tue, Sep  3, 2013 at 10:27:38PM -0400, Tom Lane wrote:
> I wrote:
> > And I will say once more that a patch that affects only the behavior of
> > eval_const_expressions can be rejected on its face.  That code has to be
> > kept in sync with the behavior of execQual.c, not just whacked around by
> > itself.  And then there are the NOT NULL constraint cases to worry about.
> 
> Hmm ... actually, it's already not in sync, because:
> 
> regression=# create table tt (x int);
> CREATE TABLE
> regression=# insert into tt values(null);
> INSERT 0 1
> regression=# select row(x) from tt;
>  row 
> -----
>  ()
> (1 row)
> 
> regression=# select row(row(x)) from tt;
>   row   
> --------
>  ("()")
> (1 row)
> 
> regression=# select row(row(row(x))) from tt;
>      row      
> --------------
>  ("(""()"")")
> (1 row)


Uh, I see the same output you show for a NULL constant:

	SELECT ROW(NULL);
	 row
	-----
	 ()
	
	SELECT ROW(ROW(NULL));
	  row
	--------
	 ("()")
	
	SELECT ROW(ROW(ROW(NULL)));
	     row
	--------------
	 ("(""()"")")

-- 
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + It's impossible for everything to be true. +