[hibernate-dev] HHH-12125 - @GeneratedValue & 5.3

[Steve Ebersole]

I just updated the text for the Jira[1].

Specifically, in the section on SEQUENCE and TABLE, at the moment I have
kept the legacy behavior of using "hibernate_sequence" as the name of the
table/sequence - users must opt-in to the behavior of using
`@GeneratedValue#generator` as the sequence/table name.  I'm thinking I'd
like to change this though - instead having the default behavior be using
`@GeneratedValue#generator` as the sequence/table name, and migrators
opting-out for the old behavior.  I think that is more consistent with how
I generally view these kind of migration settings.

Any objections to making that switch?

[1] https://hibernate.atlassian.net/browse/HHH-12125


On Sat, Nov 25, 2017 at 10:59 AM Vlad Mihalcea <mihalcea.vlad at gmail.com>
wrote:

> That's a great idea. I stumbled on this issue many times, and it's very
> good to simplify the mapping as you suggested.
>
> +1
>
> Vlad
>
> On Sat, Nov 25, 2017 at 6:18 PM, Steve Ebersole <steve at hibernate.org>
> wrote:
>
>> The background is all in the Jira, but the crux is this... it is better to
>> allow a user to do this:
>>
>>     @GeneratedValue( strategy=SEQUENCE, generator="my_seq")
>>
>> rather than:
>>
>>     @GeneratedValue( strategy=SEQUENCE, generator="my_seq")
>>     @SequenceGenerator( name="my_seq", sequenceName="my_seq" )
>>
>> You can see that `SequenceGenerator` is completely unnecessary in this
>> case
>> because it adds no new information beyond what is already available on the
>> `@GeneratedValue`.
>>
>> This works great for `GeneratedValue#strategy=SEQUENCE` and
>> `GeneratedValue#strategy=TABLE`, however consider this mapping:
>>
>>     @GeneratedValue( strategy=AUTO, generator="increment" )
>>     @GenericGenerator( name = "increment", strategy = "increment" )
>>
>> Here we have the same underlying concern - the `@GenericGenerator` is just
>> noise, it adds no additional information.  In keeping with the work done
>> as
>> part of HHH-12125 it would be great to allow users to instead just say:
>>
>>     @GeneratedValue( strategy=AUTO, generator="increment" )
>>
>> The problem here is that this last one is actually the responsibility of
>>
>> `org.hibernate.boot.model.IdGeneratorStrategyInterpreter#determineGeneratorName`
>> to interpret, but it is not passed the `GeneratedValue#generator` value.
>>
>> So the easiest solution would be to add an additional parameter to
>> `IdGeneratorStrategyInterpreter#determineGeneratorName` for passing in the
>> generator name.  The concern here is that `IdGeneratorStrategyInterpreter`
>> is defined in the API space and could very well have custom impls.
>>
>> A lesser solution wold be to add checks to the code that calls
>> `IdGeneratorStrategyInterpreter#determineGeneratorName` to check for
>> "magic" generator names before asking the
>> `IdGeneratorStrategyInterpreter`.  This is just a very inflexible and
>> non-extensible solution, but maybe this works for 5.3 and we can adjust
>> `IdGeneratorStrategyInterpreter` as part of 6.0.
>>
>> Thoughts?
>>
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>
>