Re: [eclipselink-users] Are query.setHint() calls additive?

[Laird Nelson <ljnelson@xxxxxxxxx>]

Thanks, Tom; that helps.  I assume, then, that internally EclipseLink is not using getHints() to find all the query hint values, but is rather installing those values at setHint() time directly.  (I'll look at the code.)  The specification could be much more clear on this; I'll head over to the JSR users list.

Thanks,

Best,

Laird

On Wed, May 22, 2013 at 5:22 AM, Tom Ware <tom.ware@xxxxxxxxxx> wrote:

eclipselink.join-fetch can be multiple times on the same query without issue.

There appears to be a bug in getHints() that will mean getHints() will only return the most recently added eclipselink.join-fetch hint in its map. (please feel free to enter this bug)

On 22/05/2013 12:32 AM, Laird Nelson wrote:

I'm being reintroduced to the eclipselink.join-fetch query hint.

I found a query where it would be handy to have two of these, i.e. two
join-fetch hints.

I noticed that the EclipseLink documentation
(http://wiki.eclipse.org/EclipseLink/UserGuide/JPA/Basic_JPA_Development/Query_Hints#Join_Fetch)
is mum on whether this is possible or not.

The Javadoc for the Query#setHint(String, Object) method makes it look like a
standard map operation (i.e. it should be putHint(String, Object)).  And
getHints() returns a Map, which of course would not contain duplicate keys.

But then I stumbled on this: https://github.com/mysema/querydsl/issues/348

...and that seems to suggest that duplicate keys are just fine.

I'm leery of things that happen to work.  I'd much rather trust them because
they are known to work, or are designed to work.  :-)

So: may I do something like this:

query.setHint("eclipselink.join-fetch", "a.b");
query.setHint("eclipselink.join-fetch", "a.c");

...?

Best,
Laird

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