[hibernate-dev] [OGM] Id generation strategies

[Gunnar Morling]

I'm looking into this atm.

My thinking is to pass a new dedicated Type IdGeneratorKey instead of
RowKey to GridDialect#nextVal() which can carry all the information we
need. The dual use of RowKey for association rows and sequences has been
confusing anyways.

2014-06-06 10:44 GMT+02:00 Emmanuel Bernard <emmanuel at hibernate.org>:

> I guess it is particularly questionable to have an identity generator be
> mapped to an ad-hoc table based generator. Remember the angle we came from:
> make a JPA application work when storing data in Infinispan. Unlike other
> datastores, Infinispan has not notion of id generation whatsoever.
>
> sequenceName should map to on of the OgmTableGenetator settings somehow.
>

+1


> valueColumnName is something that I elected no to use because NoSQL we
> bind to so far do not have a strong schema. And at at given
> segmentColumnValue only correspond a single value. It would come and bite
> me if someone for the same segment value had two different value column
> names to differentiate two different sequence.


Would it really bit you? I think e.g. MongoDB could perfectly handle this
case via two different fields for the two sequences in the same
document/segment.

But as this does not really seem like a best practice, we could also handle
it as a definition error if the same table is used with different value
column names in different generators. We could raise an error during
bootstrap.


> At which stage, I could invoke the What?! card. But it would make sense to
> expose that info for datastores like Cassandra.
>
> I am fine if we put the whole subject back on the table and revisit. This
> code has been written back when I was trying to prove that a brick could
> not fly.
>
> On 04 Jun 2014, at 15:36, Gunnar Morling <gunnar at hibernate.org> wrote:
>
> > Hi,
> >
> > I'm rather confused by the way how OgmIdentityGenerator,
> > OgmSequenceGenerator and OgmTableGenerator interact.
> >
> > Basically, the first two just delegate to the latter. Now intuitively I'd
> > have expected an exception when explicitly using a generation type not
> > supported on a given datastore, say @GeneratedValue(strategy =
> > GenerationType.SEQUENCE) on MongoDB. But as we always delegate to the
> table
> > strategy, such exception is not raised.
> >
> > Also several attributes of generator annotations are ignored; E.g.
> > naturally at SequenceGenerator.sequenceName(), but also
> > @TableGenerator.valueColumnName.
> >
> > What has been the motivation behind this design?
> >
> > I guess a change to GridDialect may be required for making explicit which
> > strategies are supported on a given backend.
> >
> > Thanks,
> >
> > --Gunnar
> > _______________________________________________
> > hibernate-dev mailing list
> > hibernate-dev at lists.jboss.org
> > https://lists.jboss.org/mailman/listinfo/hibernate-dev
>
>