[hibernate-dev] ORM DDL doesn't reflect BV constraints with validation mode CALLBACK

[Sanne Grinovero]

On 6 February 2018 at 14:46, Steve Ebersole <steve at hibernate.org> wrote:
> I'm not sure I would call them separate. They are clearly linked. Look at
> it this way, if we export various "validation" constraints to the database
> (DDL) it is, practically speaking, a performance overhead to also perform
> those checks in memory. Right? This is, I think, the distinction you may be
> missing in terms of DDL as a separate mode - only do these checks once, at
> the database level.

That's a grey area. Sure they are linked, as some combinations would
be nonsense, but I'd see benefits as well in being able to control
such aspects better.

In terms of performance, it might be beneficial to abort an operation
early on ("in memory") rather than have to bother the database. It's
far easier to scale a system by adding more JVMs than to scale the
RDBMs.

True it might be redundant if the business logic is perfect, but then
you'd not need validation.

> Can all such validations be handled at the database level via contraints?
> No of course not - but the vast majority in fact can.

Back in the days I've found it very useful that Hibernate ORM +
Validator + custom naming strategies, etc.. would allow me to fully
control all details of the DDL.
I used to version the DDL and have a script which gets ORM to dump it
on the same resource for each change on the model, to immediately see
the diff and understand all implications of any change on the model.
Ideal also for beginners to grow confidence in what exactly all those
annotations will do..

I'd really like to have options to still do that. I remember
complaining when Validator was standardised as IMO it lost focus from
the ORM integration; such stronger DDL integrations were available
before.

Thanks,
Sanne


>
>
>
> On Tue, Feb 6, 2018, 7:52 AM Gunnar Morling <gunnar at hibernate.org> wrote:
>
>> 2018-02-06 14:41 GMT+01:00 Steve Ebersole <steve at hibernate.org>:
>>
>>> The reasoning is that the 2 BV modes you mention make no mention of also
>>> applying constraints to the database.  It would be surprising for that to
>>> happen.  I can see the argument for AUTO, but absolutely not for CALLBACK.
>>>
>> I think that a) "trigger validation upon insert/update" and b) "propagate
>> constraints to the DDL" are two separate concerns which should be handled
>> independently.
>>
>> I.e. ideally I'd keep the "validation mode" property solely focused on a)
>> (i.e. not have that DDL enum member) and control b) (which is as you say
>> not defined by the spec) via a separate property. In fact, ORM already has
>> a property applying to b), "hibernate.validator.apply_to_ddl", although
>> it seems linked to "legacy Hibernate Validator" as per a log statement in
>> TypeSafeActivator (
>> https://github.com/hibernate/hibernate-orm/blob/master/hibernate-core/src/main/java/org/hibernate/cfg/beanvalidation/TypeSafeActivator.java#L141
>> ).
>>
>>> Also important is the distinction that hibernate accepts multivalued
>>> validation modes, whereas BV does not if I remember correctly... Although
>>> in my opinion it absolutely should.
>>>
>> "validation mode" is defined by JPA, not BV. As per above I don't think it
>> needs to be multi-valued, those two aspects can be handled separately.
>>
>>
>>
>>>
>>> On Tue, Feb 6, 2018, 7:35 AM Chris Cranford <chris at hibernate.org> wrote:
>>>
>>>> Gunnar -
>>>>
>>>> I don't particularly see a reason why we cannot as it seems we're
>>>> handling the CALLBACK mode with no BV provider present earlier in the
>>>> code path.  I'm fine changing it.
>>>>
>>>> Chris
>>>>
>>>>
>>>> On 02/04/2018 07:21 AM, Gunnar Morling wrote:
>>>> > Hi,
>>>> >
>>>> > If the JPA validation mode is set to CALLBACK, BV constraints such as
>>>> > @NotNull, @Size etc. are not reflected in the DDL created by ORM.
>>>> >
>>>> > Instead, in TypeSafeActivator, the BV constraints are only considered
>>>> for
>>>> > DDL if the validation mode is DDL or AUTO [1].
>>>> >
>>>> > CALLBACK is the safe way to ensure BV is invoked by JPA (instead of
>>>> > silently ignoring it if no BV provider is present), so it's the
>>>> setting I
>>>> > usually recommend. I think constraints should also be propagated to
>>>> DDL in
>>>> > this mode, so I'm wondering whether there a specific reason for the
>>>> current
>>>> > behaviour or wether we can change it?
>>>> >
>>>> > Thanks,
>>>> >
>>>> > --Gunnar
>>>> >
>>>> > [1]
>>>> >
>>>> https://github.com/hibernate/hibernate-orm/blob/master/hibernate-core/src/main/java/org/hibernate/cfg/beanvalidation/TypeSafeActivator.java#L146
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