[hibernate-dev] How to deal with a constant in CriteriaQuery

[Steve Ebersole]

I'd personally not like that approach.  I think specific registrations (for
extract and datediff) are better options


On Tue, Apr 24, 2018, 1:18 PM Gail Badner <gbadner at redhat.com> wrote:

> When I asked about whether JPA should support this in the future, I was
> thinking along the lines of adding something like the following
> to javax.persistence.criteria.CriteriaBuilder:
>
> Keyword keyword(String value);  // rendered as a String without quotes
>
> or:
>
> Expression<String> literal(String value, encloseInQuotes);
>
>
> On Tue, Apr 24, 2018 at 7:56 AM, Christian Beikov <
> christian.beikov at gmail.com> wrote:
>
> > Maybe we should wait until it transitioned to Eclipse then? Or do you
> > think it might make sense to start discussions already?
> >
> > The API could be String based by default but allow to "unwrap" to do
> > something provider specific. If the providers model requires it, the
> > String could be parsed by the provider.
> >
> > Imagine an API like the following
> >
> > interface SQLFunction {
> >    ExpressionType getType(FunctionContext ctx, List<ExpressionType>
> > argumentTypes);
> >    Expression render(FunctionContext ctx, List<Expression> arguments);
> >
> >    interface FunctionContext {
> >      ExpressionType getExpressionType(Class<?> javaType);
> >      Expression getExpression(String expressionString);
> >      <T> T unwrap(Class<T> clz);
> >    }
> >
> >    interface ExpressionType {
> >      Class<?> getJavaType();
> >      <T> T unwrap(Class<T> clz);
> >    }
> >
> >    interface Expression {
> >      String getExpressionString();
> >      <T> T unwrap(Class<T> clz);
> >    }
> > }
> >
> > That's just a rough idea of how it could look.
> >
> > Mit freundlichen Grüßen,
> > ------------------------------------------------------------------------
> > *Christian Beikov*
> > Am 24.04.2018 um 16:33 schrieb Steve Ebersole:
> > > JPA is technically under the old JCP still AFAIK. So for now the
> > > process would be the same it has always been.
> > >
> > > I just do not see how this would ever get agreed upon for a
> > > standardized contract - it is so very dependent upon how the provider
> > > models the query (SQM e.g.) versus the specific mechanism they use to
> > > render it (SQL AST).
> > >
> > >
> > > On Tue, Apr 24, 2018 at 9:29 AM Steve Ebersole <steve at hibernate.org
> > > <mailto:steve at hibernate.org>> wrote:
> > >
> > >     On Tue, Apr 24, 2018 at 8:45 AM Gail Badner <gbadner at redhat.com
> > >     <mailto:gbadner at redhat.com>> wrote:
> > >
> > >         Yes, that should work with CriteriaQuery as well. It's a
> > >         reasonable
> > >         workaround.
> > >
> > >         If JPA doesn't support this now, is it something that should
> > >         be supported
> > >         in the future?
> > >
> > >
> > >     The problem with defining support for this in the spec is that it
> > >     is relying on Hibernate's "SQL function registry" and its
> > >     `SQLFunction` contract.  I seriously doubt we'd get all the EG
> > >     members to agree to some standardization of anything like a
> > >     `SQLFunction` contract.
> > >
> > >     I think proposing to add additional functions to the spec as
> > >     "built-in" is probably more likely.  I can especially see EXTRACT
> > >     being likely.  Maybe DATEDIFF. Oracle for sure does not support
> > >     DATEDIFF, but it does support the EXTRACT-from-INTERVAL approach.
> > >      Anyone know offhand other databases which to not define DATEIDFF?
> > >
> > >     I personally think having DATEDIFF defined as "built-in" is the
> > >     best option as the provider can always map that to
> > >     EXTRACT-from-INTERVAL for Oracle, etal - its much harder to do
> > >     that by mapping EXTRACT-from-INTERVAL to DATEDIFF.
> > >
> >
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> >
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