On Tue, May 6, 2025 at 4:49 AM jian he <jian.universal...@gmail.com> wrote:
>
> On Sat, May 3, 2025 at 11:42 PM Robert Treat <r...@xzilla.net> wrote:
> > As such, attached patch removes the above, and attempts some clean up
> > of the documentation in ALTER TABLE to better clarify the behavior
> > around valid/not valid, enforced/not enforced, and how it affects
> > different constraints, with some additional literal tag formatting
> > changes.
> >
>
> <para>
> - Adding an enforced <literal>CHECK</literal> or <literal>NOT
> NULL</literal>
> - constraint requires scanning the table to verify that existing
> rows meet the
> - constraint, but does not require a table rewrite. If a
> <literal>CHECK</literal>
> - constraint is added as <literal>NOT ENFORCED</literal>, the validation
> will
> - not be performed.
> + Adding a <literal>CHECK</literal> or <literal>NOT NULL</literal>
> + constraint requires scanning the table to verify that existing rows meet
> + the constraint, but does not require a table rewrite. IF a
> + <literal>CHECK</literal> constraint is added as
> + <literal>NOT ENFORCED</literal>, no verification is performed.
> </para>
>
> "IF" should be "if".
Actually "If" I reckon :-)
> i don't know which one ("validation" or "verification") is more accureate,
> but i found this
> (https://www.eviltester.com/2018/09/no-verification-validation.html)
>
I intentionally chose verification as a callback to the earlier
mention that the table will be scanned to *verify* the rows. I also
want to put some distance between the ENFORCED / NOT ENFORCED language
and NOT VALID / VALIDATE CONSTRAINT commands, which is a separate
feature/functionality on it's own.
> here, we should also mention <literal>FOREIGN KEY</literal> constraint?
>
I didn't think it felt necessary based on other information elsewhere
(and wasn't there before).
>
> - This form validates a foreign key, check, or not-null constraint that
> was
> - previously created as <literal>NOT VALID</literal>, by scanning the
> + This form validates a <literal>FOREIGN KEY</literal>,
> + <literal>CHECK</literal>, or <literal>NOT NULL</literal> constraint
> that
> + was previously created as <literal>NOT VALID</literal>, by scanning the
> table to ensure there are no rows for which the constraint is not
> - satisfied. If the constraint is not enforced, an error is thrown.
> + satisfied. If the constraint was created as
> + <literal>NOT ENFORCED</literal>, an error is thrown.
> I think this changes should be great. original text
> "If the constraint is not enforced" can mean "some exists row not
> satisfied the constraint
> condition" or "the constraint is marked as <literal>NOT ENFORCED</literal>".
Yeah, "not enforced" felt a little loose to me, especially since the
only way a constraint can be NOT ENFORCED is if it was created that
way (not to mention you can't change it later, you have to drop it).
Robert Treat
https://xzilla.net
