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

[Vlad Mihalcea]

HI,

I think I'll have to make it a little bit more clear in the docs as well. I
Knew about Hibernate comments and assumed they could be used as hints.

Now, that I look back on the Query API I see they were added in 4.3:

http://docs.jboss.org/hibernate/orm/4.3/javadocs/org/hibernate/Query.html#addQueryHint(java.lang.String)

But I can't find it in 4.2:

http://docs.jboss.org/hibernate/orm/4.2/javadocs/org/hibernate/Query.html

I will adjust my PR accordingly so that the comment on @NamedQuery will
only be propagated if the associated Hibernate property is set.
As for @NamedNativeQuery, I think we need to support it since we have the
comment attribute on the annotation level.

Vlad

On Tue, Aug 1, 2017 at 6:16 PM, Steve Ebersole  wrote:

> See inline..
>
> On Tue, Aug 1, 2017 at 9:05 AM Vlad Mihalcea 
> wrote:
>
>> I created a new Pull Request so that comments can be handled for named
>> queries (even for UPDATE/DELETE queries):
>>
>> https://github.com/hibernate/hibernate-orm/pull/1970
>>
>
> Not really following this.  See `org.hibernate.annotations.NamedQuery#comment`
> and `org.hibernate.annotations.QueryHints#COMMENT`.  So we do support
> this for named queries.  Hints are generally only useful (if at all) for
> SELECTs.  Comments can be useful for any type of statement, but again we
> have the support for those in place in regards to named queries.
>
>
> I think we should add two new issues;
>>
>> 1. So that we could pass Query Hints for Named (Native) Queries as well.
>> Right now we can only pass comments which are appended at the beginning of
>> the SQL statement.
>>
>
> I completely disagree about supporting comments and/or hints for native
> SQL queries.
>
> As for "[we only support] comments which are appended at the beginning of
> the SQL statement" - that is true for comments.  However, it is inaccurate
> for hints - see `org.hibernate.dialect.Dialect#getQueryHintString`.  So
> the hook is in place for handling this for hints.  There is no such hook
> for comments - do you concretely know of a Dialect that supports a comment
> elsewhere than the start?  I'm a little leery of adding support for this
> pre-6.0 as we know for certain that this will change (String-based versus
> AST-based).  If you wan to add such a hook in 6.0, I am ok with that -
> provided you can show me such a concrete use case.
>
>
>
>
>> 2. I see we support Query Hints for Oracle and SQL Server. We should
>> support MySQL as well:
>>
>> https://dev.mysql.com/doc/refman/5.7/en/optimizer-hints.html
>>
>
> Sure - I think its a good idea to support this where ever  the underlying
> database supports it.
>
>
> If you have time to take a look on the PR, let me know what you think.
>>
>
> I'll take a look at the PR after we resolve these general points and they
> are incorporated into the PR.
>
>
>
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Re: [hibernate-dev] Difference between Comment and Hint in Hibernate query

[Vlad Mihalcea]

I created a new Pull Request so that comments can be handled for named
queries (even for UPDATE/DELETE queries):

https://github.com/hibernate/hibernate-orm/pull/1970

I think we should add two new issues;

1. So that we could pass Query Hints for Named (Native) Queries as well.
Right now we can only pass comments which are appended at the beginning of
the SQL statement.
2. I see we support Query Hints for Oracle and SQL Server. We should
support MySQL as well:

https://dev.mysql.com/doc/refman/5.7/en/optimizer-hints.html

If you have time to take a look on the PR, let me know what you think.

Thanks

On Tue, Aug 1, 2017 at 4:28 PM, Steve Ebersole  wrote:

> 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 
> 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 
>> 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 
>>> 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 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
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>>>
>>
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Re: [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  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 
> 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 
>> 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 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@lists.jboss.org
>>> https://lists.jboss.org/mailman/listinfo/hibernate-dev
>>>
>>
>
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Re: [hibernate-dev] Difference between Comment and Hint in Hibernate query

[Vlad Mihalcea]

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  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 
> 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 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
>> ___
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>> hibernate-dev@lists.jboss.org
>> https://lists.jboss.org/mailman/listinfo/hibernate-dev
>>
>
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Re: [hibernate-dev] Difference between Comment and Hint in Hibernate query

[Steve Ebersole]

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

[Vlad Mihalcea]

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 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
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