| Michael Bouschen 2006-02-10, 7:45 am |
| Hi,
I have the same understanding of the semantics of projections of
collection and map fields as Wes and Bin Sun. The query would return the
collections or maps as single cells, so the query result would be a list
of collections or maps. I also agree that support for projections of
collection and map fields does not add much value, but AFAIK the current
spec allows this.
I think the shape of the query result is different whether projecting a
collection field or including a variable in the result that iterates the
collection:
(1) SELECT employees FROM Department
(2) SELECT e FROM Department WHERE employees.contains(e)
The first query returns a list of collections of employees, so for each
department it returns the department's employee collection. Query (2)
returns a list of employees, where each returned employee is included in
an employee collection of at least one department.
Given the above is correct, JDOQL would never return Map.Entry
instances. Either the query projects the entire map or it iterates the
map using containsKey or containsValue, but there is no contains for maps.
Regards Michael
> Hi, all!
>
> If I didn't miss anything in the spec, I would
> expect 'single-cell' result for a collection or map
> field, as if it is a simple field or reference field.
>
> eg.
>
> "select employees from Department"
> -->
> [employees of Dept 1]
> [employees of Dept 2]
> [employees of Dept 3]
> ...
>
> Assume Student.scores: Map<Course, Float>
> "select name, scores from Student"
> -->
> aaa,[scores map for aaa]
> bbb,[scores map for bbb]
> ccc,[scores map for ccc]
>
>
> --- erik@jpox.org wrote:
>
>
>
>
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--
Michael Bouschen Tech@Spree Engineering GmbH
mailto:mbo.tech@spree.de http://www.tech.spree.de/
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|