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Re: Re: starting to review the Extend NOT NULL representation to pg_constraint patch

From: Alvaro Herrera <alvherre(at)commandprompt(dot)com>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com>, Bernd Helmle <mailings(at)oopsware(dot)de>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Andrew Geery <andrew(dot)geery(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>, Bruce Momjian <bruce(at)momjian(dot)us>
Subject: Re: Re: starting to review the Extend NOT NULL representation to pg_constraint patch
Date: 2011-06-29 16:51:20
Message-ID: 1309366105-sup-9805@alvh.no-ip.org (view raw or flat)
Thread:
Lists: pgsql-hackers
Excerpts from Robert Haas's message of lun jun 27 10:35:59 -0400 2011:
> On Mon, Jun 27, 2011 at 3:08 AM, Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com> wrote:

> > I would summarise the consistency requirements as:
> >
> > 1). ADD CONSTRAINT should leave both parent and child tables in the
> > same state as they would have been if the constraint had been defined
> > at table creation time.
> >
> > 2). DROP CONSTRAINT should leave both parent and child tables in the
> > same state as if the constraint had never existed (completely
> > reversing the effects of ADD CONSTRAINT).
> >
> > I don't have a strong opinion as to whether or not the NOT NULL part
> > of a PK should be inherited, provided that it is consistent with the
> > above.
> >
> > I guess that if I were forced to choose, I would say that the NOT NULL
> > part of a PK should not be inherited, since I do think of it as part
> > of the PK, and PKs are not inherited.
> 
> OK, I see your point, and I agree with you.

Interesting.  This whole thing requires quite a bit of rejiggering in
the initial transformation phase, I think, but yeah, I see the points
here and I will see to them.  Does this mean that "NOT NULL PRIMARY KEY"
now behaves differently?  I think it does , because if you drop the PK
then the field needs to continue being not null.

And here I was thinking that this was just a quick job to enable NOT
VALID constraints ...

-- 
Álvaro Herrera <alvherre(at)commandprompt(dot)com>
The PostgreSQL Company - Command Prompt, Inc.
PostgreSQL Replication, Consulting, Custom Development, 24x7 support

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