[hibernate-dev] Difference between Comment and Hint in Hibernate query

[Steve Ebersole]

They have different intentions and are potentially applied in different
ways for different databases - hence separate.

E.g. DB2 supports a query comment, but does not support optimizer hints...
so these need to be handled differently

On Tue, Aug 1, 2017, 8:19 AM Vlad Mihalcea <mihalcea.vlad at gmail.com> wrote:

> I'm asking because the
>
> org.hibernate.annotations.NamedNativeQuery or
> org.hibernate.annotations.NamedQuery
>
> define the comment attribute with the following Javadoc:
>
> /**
>  * A comment added to the generated SQL query.  Useful when engaging with DBA.
>  */
> String comment() default "";
>
> So, Hibernate clients could use the comment attribute in order to supply
> an Oracle query hint, right?
>
> In this case, should we treat this attribute as a query hint so that the
> Oracle/SQL Server hint logic applies to this one as well?
>
> Vlad
>
> On Tue, Aug 1, 2017 at 4:07 PM, Steve Ebersole <steve at hibernate.org>
> wrote:
>
>> Query hints are hints for the database' s query parser/optimizer.
>>
>> A comment is a... well a comment :)
>>
>> On Tue, Aug 1, 2017, 6:37 AM Vlad Mihalcea <mihalcea.vlad at gmail.com>
>> wrote:
>>
>>> Hi,
>>>
>>> While working on integrating a Pull Request, I realized that the
>>> org.hibernate.engine.spi.QueryParameters provides these two attributes:
>>>
>>> private String comment;
>>> private List<String> queryHints;
>>>
>>> Both these two are to be sent to the database, so why do we have both?
>>>
>>> I also noticed that only for Query Hints we do take into consideration DB
>>> specific query hint syntax:
>>>
>>> // Keep this here, rather than moving to Select.  Some Dialects may
>>> need the hint to be appended to the very
>>> // end or beginning of the finalized SQL statement, so wait until
>>> everything is processed.
>>> if ( parameters.getQueryHints() != null &&
>>> parameters.getQueryHints().size() > 0 ) {
>>>    sql = dialect.getQueryHintString( sql, parameters.getQueryHints() );
>>> }
>>>
>>> Shouldn't we only have either comment or queryHints? Or what is the
>>> difference between these two?
>>>
>>> Vlad
>>> _______________________________________________
>>> hibernate-dev mailing list
>>> hibernate-dev at lists.jboss.org
>>> https://lists.jboss.org/mailman/listinfo/hibernate-dev
>>>
>>
>