Re: comparing NEW and OLD (any good this way?)

From: "Daniel Verite" <daniel(at)manitou-mail(dot)org>
To: pgsql-general(at)postgresql(dot)org
Subject: Re: comparing NEW and OLD (any good this way?)
Date: 2009-08-18 08:32:35
Message-ID: ffaec335-2565-473b-ba4d-eab9deaa2e79@mm
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Sam Mason wrote:

> I've just realized another case where it's not consistent; why does the
> following return true:
>
> SELECT row(null) IS NULL;
>
> and yet the following false:
>
> SELECT row(row(null)) IS NULL;

You're intentionally assuming that row(null) IS NULL evaluating to true
implies that row(null) can be replaced by NULL. As discussed upthread, this
is not the case.

> I think I'm saying that PG should be deliberately breaking specified
> behavior and go back to pre-8.2 behavior in this regard.

But let's run your example with 8.1:

# SELECT row(null) IS NULL;
?column?
----------
t

# SELECT row(row(null)) IS NULL;
?column?
----------
f

These are the same results that you say are inconsistant, so pre-8.2 behavior
doesn't help here...

Best regards,
--
Daniel
PostgreSQL-powered mail user agent and storage: http://www.manitou-mail.org

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