[hibernate-dev] Mapping JPA's @MapKeyEnumerated and @Enumerated on native-enum supporting datastores

[Steve Ebersole]

PGSQL has some enum support I know.  The problem has always been that they
are mapped to "special" type codes (think java.sql.Types) which makes it
difficult to work with in ORM.



On Fri, Aug 26, 2016 at 6:18 AM Gunnar Morling <gunnar at hibernate.org> wrote:

> > I guess we could, but it's sad that we'd still have to default to the
> > "wrong" mapping,
> > at least for all those people who won't read all of our docs.
>
> The default for our custom @Enumerated could be NATIVE, but I agree people
> need to know about that instead of the JPA one.
>
> > Would that live in OGM or ORM ?
>
> Good question, depends on whether there is any RDBMS with native enum
> support?
>
>
> 2016-08-26 13:02 GMT+02:00 Sanne Grinovero <sanne at hibernate.org>:
>
> > On 26 August 2016 at 10:34, Gunnar Morling <gunnar at hibernate.org> wrote:
> > > How about having a custom @Enumerated annotation which offers NATIVE as
> > an
> > > additional choice?
> >
> > I guess we could, but it's sad that we'd still have to default to the
> > "wrong" mapping,
> > at least for all those people who won't read all of our docs.
> >
> > Would that live in OGM or ORM ?
> >
> > >
> > > 2016-08-26 10:16 GMT+02:00 Emmanuel Bernard <emmanuel at hibernate.org>:
> > >>
> > >> Can you give HotRod's example of native enum - I imagine Protobuf ?
> >
> > From the OGM testsuite:
> >
> > @Entity
> > public class Bookmark {
> >
> > public enum Classifier {
> > HOME, WORK
> > }
> >
> > @Id
> > private String id;
> > @Enumerated(EnumType.STRING)
> > private Classifier classifier;
> > [...]
> > }
> >
> > Is mapped as:
> >
> >   message Bookmark {
> >     required string id = 1;
> >     optional string classifier = 2;
> >   [...]
> >
> > (correctly as it's explicitly requesting a STRING EnumType)
> >
> > A more "native" Protobuf mapping would look like:
> >
> >   enum Classifier {
> >     HOME = 0;
> >     WORK = 1;
> >   }
> >
> >   message Bookmark {
> >     required string id = 1;
> >     optional Classifier classifier = 2;
> >   [...]
> >
> > I had already implemented this, just realising later that there's no
> > way to enable this better looking mapping.
> >
> > >>
> > >> The issue I see is that ordinal could be an acceptable explicit
> decision
> > >> that would not be available to the user if you use default as native.
> > >>
> > >> I'm tempted to go native all the time at the detriment of people that
> > >> need high customization.
> >
> > I'd be tempted too as the second mapping looks much more natural,
> > however this would break things for people who need it to be an
> > integer, e.g. if they have other clients who expect an int.
> > On the other hand, the "I need compatibility with another client"
> > argument is quite weak, as at this stage the Hot Rod Dialect generates
> > its own schema and pretty much mandates using the one it generates.
> >
> > Proposal: I have it mapped as "native enums" by default, and give a
> > global configuration property to honour the annotations instead? This
> > would be a global setting though, so if one wants one attribute
> > "native encoded" and another "int encoded" that wouldn't be possible.
> >
> > Thanks,
> > Sanne
> >
> > >>
> > >> Emmanuel
> > >>
> > >> On Mon 2016-08-15 18:14, Sanne Grinovero wrote:
> > >> > In the context of Hibernate OGM, it turns out that some datastores
> > >> > have a rather nice "native" support for enums.
> > >> >
> > >> > We aim to map each property of the user's domain model to its most
> > >> > appropriate "physical type", unless the choice is overriden by the
> an
> > >> > explicit user request.
> > >> >
> > >> > In the case of an Enum, JPA annotations such as @Enumerated have an
> > >> > attribute EnumType to choose the physical representation:
> > >> >
> > >> > public enum EnumType {
> > >> >     /** Persist enumerated type property or field as an integer. */
> > >> >     ORDINAL,
> > >> >
> > >> >     /** Persist enumerated type property or field as a string. */
> > >> >     STRING
> > >> > }
> > >> >
> > >> > However, there's no support for a "NATIVE". Also, the annotation
> > >> > specifies that "ORDINAL" is the default value so I can't just assume
> > >> > that the user didn't specify anything and we're good to use our own
> > >> > NATIVE implementation.
> > >> >
> > >> > Assuming that we can't change the JPA spec, any suggestion on when I
> > >> > could have the Hot Rod dialect for OGM to actually produce a "nice"
> > >> > mapping into native enums?
> > >> >
> > >> > I'm tempted to just use natives all the time; In the case in which
> the
> > >> > user opted for "STRING" I could drop a warning - or decide to honour
> > >> > that - but in case of ORDINAL I just can't tell if it's a default
> > >> > choice or not so I think a warning would be too much.
> > >> >
> > >> > Another alternative would be that I "go native" when the @Enumerated
> > >> > annotation isn't specified at all: looks like this mapping is valid
> > >> > according to ORM as it seems to treat it as if there was an implicit
> > >> > @Enumerated annotation; I'm not happy about having to rely on people
> > >> > to not use an explicit annotation though.
> > >> >
> > >> > Thanks,
> > >> > Sanne
> > >> > _______________________________________________
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> > >
> >
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