From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | Bruce Momjian <bruce(at)momjian(dot)us> |
Cc: | Hannu Krosing <hannu(at)2ndQuadrant(dot)com>, Peter Eisentraut <peter_e(at)gmx(dot)net>, Andrew Dunstan <andrew(at)dunslane(dot)net>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: strange IS NULL behaviour |
Date: | 2013-09-04 02:27:38 |
Message-ID: | 13916.1378261658@sss.pgh.pa.us |
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Lists: | pgsql-hackers |
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)
There's certainly no excuse for this behaving differently from the cases
with a simple constant NULL. So I'm a bit inclined to say that we should
rip out the special case in eval_const_expressions, not make it even less
self-consistent. It's possible to argue that existing applications won't
be too sensitive to the behavior of the constant cases, but they surely
must be depending on the behavior in the non-constant cases.
regards, tom lane
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