Re: CHECK Constraint Deferrable

On Fri, Sep 8, 2023 at 1:23 PM Dilip Kumar <dilipbalaut(at)gmail(dot)com> wrote:

> 2.
> - if ((failed = ExecRelCheck(resultRelInfo, slot, estate)) != NULL)
> + if ((failed = ExecRelCheck(resultRelInfo, slot, estate,
> checkConstraint, &recheckConstraints)) != NULL && !recheckConstraints)
>
>
> Why recheckConstraints need to get as output from ExecRelCheck? I
> mean whether it will be rechecked or nor is already known by the
> caller and
>
Yes it will be known to the caller but ExecRelCheck will set this new
parameter only if any one of the constraint is defined as Deferrable (in
create table statement) and there is a potential constraint violation.

> Whether the constraint failed or passed is known based on the return
> value so why do you need to extra parameter here?
>
> Because if normal CHECK constraint(non Deferrable) is violated, no need to
proceed with the insertion and in that case recheckConstraints will hold
"false" but if Deferrable check constraint is violated, we need to
revalidate the constraint at commit time and recheckConstraints will hold
"true".

>
> 5.
> +typedef enum checkConstraintRecheck
> +{
> + CHECK_RECHECK_DISABLED, /* Recheck of CHECK constraint is disabled, so
> + * DEFERRED CHECK constraint will be
> + * considered as non-deferrable check
> + * constraint. */
> + CHECK_RECHECK_ENABLED, /* Recheck of CHECK constraint is enabled, so
> + * CHECK constraint will be validated but
> + * error will not be reported for deferred
> + * CHECK constraint. */
> + CHECK_RECHECK_EXISTING /* Recheck of existing violated CHECK
> + * constraint, indicates that this is a
> + * deferred recheck of a row that was reported
> + * as a potential violation of CHECK
> + * CONSTRAINT */
> +} checkConstraintRecheck;
>
> I do not like the naming convention here, especially the words
> RECHECK, DISABLE, and ENABLE. And also the name of the enum is a bit
> off. We can name it more like a unique constraint
> YES, PARTIAL, EXISTING
>
> I can think of alternative ENUM name as "EnforceDeferredCheck" and member
as “CHECK_DEFERRED_YES”, “CHECK_DEFRRED_NO” and “CHECK_DEFERRED_EXISTING”.

Thoughts?
--
Regards,
Himanshu Upadhyaya
EnterpriseDB: http://www.enterprisedb.com