Session.Query<Registration>()
.Where(r => (theDate < r.Start || today <= r.End))
.OrderBy(r => r.Start)
.FetchMany(r => r.People)
.ThenFetch(p => p.Location) //optional
.ToList();
2014-12-05 20:48 GMT+01:00 Steve Brown <[email protected]>:
> I have an entity model along the lines of the following:
>
> public class Registration
> {
> public virtual int Id { get; set; }
> public virtual DateTime Start { get; set; }
> public virtual DateTime End { get; set; }
> public virtual IList<Person> People { get; set; }
> }
>
> public class Person
> {
> public virtual int Id { get; set; }
> public virtual Registration Registration { get; set; }
> public virtual string Name { get; set; }
> public virtual Location Location { get; set; }
> }
>
> public class Location
> {
> public virtual int Id { get; set; }
> public virtual string Description { get; set; }
> }
>
> Currently, the Registration.People collection is lazy loaded, and the
> Person.Location property is fetched with a join when loading a Person
> entity.
>
> I have a view that needs to load all registration entities on a particular
> day. I have created the query easily enough and it returns the expected
> results:
>
> DateTime theDate = DateTime.Today;
> Session.Query<Registration>()
> .Where(r => (theDate < r.Start || today <= r.End))
> .OrderBy(r => r.Start)
> .ToList();
>
> However with my existing model, NHibernate issues a query to fetch the
> Registration entities, then* for each Registration found*, issues another
> query to fetch the Person entities. While this certainly works, it results
> in a lot of queries if there are a lot of Registration records on a
> particular day.
>
> I'm wondering if there is a more efficient way to fetch the child
> records? For example, if I were stuck using ADO.NET and building my
> queries by hand, I might query all the Registration records, collect the
> Ids of the returned entities, then issue a single query for Person entities
> with Registration Ids in the collection, then map the Person entities back
> to the appropriate Registration record. I've looked at Futures and eager
> fetching the children, but those produced ugly results (like Cartesian
> result sets, etc.). Can I accomplish something similar with NHibernate?
>
> TIA,
> Steve
>
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