| From: | Isaac Morland <isaac(dot)morland(at)gmail(dot)com> |
|---|---|
| To: | Ashutosh Bapat <ashutosh(dot)bapat(dot)oss(at)gmail(dot)com> |
| Cc: | Álvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, Peter Eisentraut <peter(at)eisentraut(dot)org>, Amul Sul <sulamul(at)gmail(dot)com>, jian he <jian(dot)universality(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Joel Jacobson <joel(at)compiler(dot)org>, Suraj Kharage <suraj(dot)kharage(at)enterprisedb(dot)com> |
| Subject: | Re: NOT ENFORCED constraint feature |
| Date: | 2025-02-14 15:15:07 |
| Message-ID: | CAMsGm5fZUznaA2Ae2FKrw_UUY=s0tZndWwr+cfSeSBjsDKj=uQ@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Fri, 14 Feb 2025 at 10:11, Ashutosh Bapat <ashutosh(dot)bapat(dot)oss(at)gmail(dot)com>
wrote:
> > > I think, what you intend to say is clearer with 4 state system {NE, E}
> > > * {NV, V} = {(NE, NV), (NE, V), (E, NV), (E, V)} where (NE, V) is
> > > unreachable. Let's name them S1, S2, S3, S4 respectively.
> > [...]
> > > Notice that there are no edges to and from S2.
> >
> > So why list it as a possible state?
>
> For the sake of combinatorics. :)
>
Just because there are 2^n combinations of n boolean values does not mean
there are 2^n actual meaningful states. That's why we have CHECK
constraints.
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