[hibernate-issues] [Hibernate-JIRA] Created: (HHH-5305) selecting elements from a collection of elements fails strangely

[Karsten Behrmann (JIRA)]

selecting elements from a collection of elements fails strangely
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                 Key: HHH-5305
                 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-5305
             Project: Hibernate Core
          Issue Type: Improvement
          Components: query-hql
    Affects Versions: 3.5.1
         Environment: PostgreSQL / hsqldb
            Reporter: Karsten Behrmann


The query
"select el from Foo f join f.elements el"
produces a SQL select clause for merely "elements.id" (though joined correctly),
if "elements" is a set of composite-element.

It should rather select for all properties of the composite-element.


Effect:
- If there is no column called "id", the query fails database parse
(provoke by explicitly doing <key column="fooID" />)

- If the composite-element has more than one property, hibernate ResultSet parsing fails asking for missing col_0_1_

- If the composite-element has one property, assignment-compatible with whatever the database column "id" happens to be, the query succeeds, returning a list of elements with the property set to the value of "id".


So it seems like support is almost there. This may be a regression, or a not-quite-completed feature. Succeeding quietly with bad data is Not Good, but the case should not occur much in practice (composite-element with one property is not very useful).

Workaround: explicitly select each property, as in
"select el.name, el.created, el.importance from Foo f join f.elements el"
and manually instantiate the element class.
(This seems to still fail on <any> properties, but that is probably an unrelated problem)

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