Re: information_schema and not-null constraints

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От David G. Johnston
Тема Re: information_schema and not-null constraints
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Msg-id CAKFQuwZJmP3bTkc2dRYySy2XXDdxx-xzVQu3sGd8bRtg+GcYwA@mail.gmail.com
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Ответ на Re: information_schema and not-null constraints  (Vik Fearing <vik@postgresfriends.org>)
Ответы Re: information_schema and not-null constraints  (Vik Fearing <vik@postgresfriends.org>)
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On Tue, Sep 5, 2023 at 2:50 PM Vik Fearing <vik@postgresfriends.org> wrote:
On 9/5/23 19:15, Alvaro Herrera wrote:
> On 2023-Sep-05, Alvaro Herrera wrote:
>
> Looking now at what to do for CHECK_CONSTRAINTS with domain constraints,
> I admit I'm completely confused about what this view is supposed to
> show.  Currently, we show the constraint name and a definition like
> "CHECK (column IS NOT NULL)".  But since the table name is not given, it
> is not possible to know to what table the column name refers to.  For
> domains, we could show "CHECK (VALUE IS NOT NULL)" but again with no
> indication of what domain it applies to, or anything at all that would
> make this useful in any way whatsoever.

Constraint names are supposed to be unique per schema[1] so the view
contains the minimum required information to identify the constraint.

I'm presuming that the view constraint_column_usage [1] is an integral part of all this though I haven't taken the time to figure out exactly how we are implementing it today.

I'm not all that for either A or B since the status quo seems workable.  Though ideally if the system has unique names per schema then everything should just work - having the views produce duplicated information (as opposed to nothing) if they are used when the DBA doesn't enforce the standard's requirements seems plausible.

David J.



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