I'm trying to write a query in NHibernate. I don't really care if I use the Criteria API or HQL, I just can't figure out how to write the query.
Here's my model:
public class LogEntry { public DateTime TimeCreated { get; set; } }
public class Note : LogEntry { public string Content { get; set; } }
public class Workflow { public IList<LogEntry> Log { get; set; } }
I want the query to return all Workflows that which contain a Note with specific words in the Content of the note.
In pseudo-SQL, I'd write this like:
select w.*
from Workflow w
join w.Log l where l is class:Note
where (Note)l.Content like '%keyword%'
I'm not sure about the Criteria API, but HQL seems to handle polymorphic queries quite well, even when searching on a property that only exists in a specific sub-class. I would expect the following to work:
from Workflow w join w.Log l where l.class = Note and l.Content like '%keyword%'
I don't know if there is a better way, but I use subqueries for this:
from Workflow w
join w.Log l
where l in (
select n
from Note n
where n.Content like '%keyword%'
)
(if this doesn't work, write l.id in (select n.id...)
In criteria, you can directly filter properties that are only available on a subclass, but you shouldn't, because it only filters for the first subtype it finds where this property is defined.
I use subqueries as well:
DetachedCriteria subquery = DetachedCriteria.For<Note>("n")
.Add(Expression.Like("n.Content", "%keyword%"))
.SetProjection(Projections.Property("n.id"));
IList<Workflow> workflows = session.CreateCriteria<Workflow>("w")
.CreateCriteria("w.Log", "l")
.Add(Subqueries.PropertyIn("l.id", subquery))
.List<Workflow>();
