[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 <steve at hibernate.org> wrote:

> See inline..
>
> On Tue, Aug 1, 2017 at 9:05 AM Vlad Mihalcea <mihalcea.vlad at gmail.com>
> 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.
>
>
>