10:52 a.m.
I'd prefer that IDENTITY never be the native generator any time we add a
new Dialect. Native is a Hibernate-only concept and so we can really
choose whatever we want for native generators. Also native is an outdated
concept, replaced by AUTO and SequenceStyleGenerator. IMO we should never
be choosing IDENTITY for identifier generation unless a user explicitly
asks for it. So for the first piece, Oracle12cDialect should
override getNativeIdentifierGeneratorClass to
return SequenceStyleGenerator. The Dialect implementation
of getNativeIdentifierGeneratorClass really assumes databases which support
IDENTITY but not SEQUENCE. Oracle12cDialect is the first case we have had
where a database that historically supported SEQUENCES has added support
for IDENTITY and we just did not account for that properly. In fact, the
"proper" solution would be to go into the base Oracle Dialect(s) and
override getNativeIdentifierGeneratorClass to just always
return SequenceStyleGenerator. But doing that in SequenceStyleGenerator
only is viable too.
As for how to get IDENTITY generation to work consistently with Oracle,
that I cannot say. I asked Oscar (the reporter of HHH-9983) for find out
the way to get IDENTITY generation to work with Oracle 12c *via JDBC*.
"Via JDBC" is the operative part. All of the Oracle documentation and
google hits at that time only discussed using IDENTITY via command told
(SQLPlus, etc). According to his findings we seem to have to correct.
IIUC you are saying that the problem is porting that from 5.1 (master) to
5.0? Due to an SPI change? What exactly is the SPI that changed? We did
make lots of changes to "IdentityColumnSupport" (adding that as a
first-class contract), but that is really just cosmetic grouping of stuff
already available on Dialect. So what change specifically stops you from
porting those changes to 5.0?
On Thu, Dec 24, 2015 at 4:58 AM Emmanuel Bernard <emmanuel(a)hibernate.org>
wrote:
I think my preference would be to override in Oracle*Dialect
getNativeIdentifierGeneratorClass so that it always returns
SequenceStyleGenerator
1. it would be backward compatible with the logic we had for ever (with
the exception of 5.0 but I understand that it is not really reliable)
2. I suppose sequences are still the preferred choices for Oracle DB DBAs.
Emmanuel
> On 24 Dec 2015, at 02:46, Gail Badner <gbadner(a)redhat.com> wrote:
>
> Oracle12cDialect was added in 5.0 by HHH-9044. Unfortunately there are
> problems with the new identity support that Oracle12cDialect introduced
> (HHH-9983). The fix for HHH-9983 involved SPI changes, so it was applied
to
> master for 5.1 (only).
>
> A couple of weeks ago, Andrea found that identities seemed to work using
> 5.0 when running BulkManipulationTest using Oracle JDBC 12.1.0.1.0. At
the
> same time it failed for me in the same way as HHH-9983 using 12.1.0.2.0.
> Then Andrea and I switched the JDBC versions (Andrea tried 12.1.0.1.0; I
> tried 12.1.0.2.0) and we were both able to run BulkManipulationTest
> successfully. This was very strange, especially since we were using the
> same Oracle instance, each using a different user. I didn't see any
> difference in how we were setting Hibernate properties. Several days
later,
> I tried Oracle JDBC 12.1.0.2.0 again, but BulkManipulationTest was
failing
> again in the same way as HHH-9983.
>
> Does anyone know how to get Oracle12cDialect's identity support to work
for
> 5.0 reliably? Is there some version of Oracle JDBC or DB configuration
that
> is required?
>
> If so, please let me know. The rest of this email assumes it is not
> possible. If I'm missing some configuration detail, then just ignore the
> rest of this message.
>
> When the unit tests are run using Oracle12cDialect on 5.0, there are many
> failures:
> * tests with entities explicitly mapped to use an identity fail; these
> failures did not happen in 4.3 using Oracle10gDialect because these tests
> where skipped (because Oracle10cDialect#supportsIdentityColumns returns
> false)
> * use @GeneratedValue with default strategy or use hbm mapping for ID
> <generator class="native"/>; these failures did not happen in 4.3
because
> the native generator for Oracle10gDialect uses a sequence; the native
> generator for Oracle12cDialect uses an identity.
>
> Also, starting in 5.0, when using Oracle 12c, StandardDialectResolver
will
> automatically resolve to Oracle12cDialect if the dialect is not
explicitly
> mapped. Previously it would have resolved ot Oracle10gDialect.
>
> I would be OK with changing the native generator in 5.0 from sequence to
> identity if identities were working properly. I think it will cause
> confusion when applications break. To get things working with 5.0,
> applications will need to explicitly set the dialect to Oracle10gDialect,
> extend Oracle12cDialect to disable identity support, or change ID
mappings
> to specify sequences.
>
> Here are some alternatives to get things working.
>
> Alternative A:
> 1) for 5.0 through 5.x override Dialect#getNativeIdentifierGeneratorClass
> to return SequenceStyleGenerator.class; I suggest the change for 5.x
> because I don't think it would be an acceptable to change the native
> generator for Oracle12cDialect from using a sequence to using an identity
> in 5.x;
> 2) for 5.0 only, remove support for identities;
> 3) for 6.0, if desireable, extend Oracle12gDialect (or whatever is
current
> at that time) to change the native generator to use an identity.
>
> Alternative B:
> 1) for 5.0 through 5.x, leave Oracle12cDialect as is, and add a new
dialect
> with native generator that uses a sequence (i.e.,
> Oracle12cNativeSequenceGeneratorDialect or something else that is not so
> ugly);
> 2) for 5.0 through 5.x, change StandardDialectResolver to automatically
> resolve to Oracle12cNativeSequenceGeneratorDialect for Oracle 12g server.
>
> Alternative C:
> 1) for 5.0 through 5.x, change native generator for Oracle12cDialect to
use
> sequence; leave identity support as is (broken in 5.0; fixed in 5.1);
> 2) for 5.0 through 5.x, add a new dialect with native generator that uses
> an identity (Oracle12cNativeIdentityGeneratorDialect or something else
that
> is not so ugly).
> 3) change StandardDialectResolver to automatically resolve to
> Oracle12cDialect for Oracle 12g server.
>
> I prefer alternative A. Alternatives B and C involve maintaining 2
dialects
> for the same Oracle version; I would think that one of them would be
> deprecated moving forward.
>
> Thoughts?
>
> Thanks,
> Gail
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