Linq to Nhibernate with Contains and SubString does not work? - tsql

Question

There appears to be mismatch betweeen the SQL generated by NHibernate and SQL expected by SQL2008 in the following case:
public void PersistPerson()
{
var sessionFactory = CreateSessionFactory();
using (var session = sessionFactory.OpenSession())
{
using(var transaction = session.BeginTransaction())
{
session.Save(new Person {FirstName = "Foo", LastName = "Bar"});
session.Save(new Person {FirstName = "Foo", LastName = "Dah"});
session.Save(new Person {FirstName = "Foo", LastName = "Wah"});
transaction.Commit();
}
}
using (var session = sessionFactory.OpenSession())
{
using(var transaction = session.BeginTransaction())
{
var queryable = from p in session.Query<Person>() select p;
var lastNames = new[]{"B", "D"};
var result = queryable.Where(r => lastNames.Contains(r.LastName.Substring(0, 1))).ToList();
transaction.Commit();
Assert.That(result[0].LastName, Is.EqualTo("Bar"));
}
}
}
The resulting sql query generated by NHibernate for
var result = queryable.Where(r => lastNames.Contains(r.LastName.Substring(0, 1))).ToList();
is:
select person0_.Id as Id0_,
person0_.FirstName as FirstName0_,
person0_.LastName as LastName0_ from [Person] person0_ where upper(substring(person0_.LastName,
0 /* #p0 */,
1 /* #p1 */)) in ('B' /* #p2 */)
From the MSDN documentation for T-SQL SUBSTRING
http://msdn.microsoft.com/en-us/library/ms187748.aspx
SUBSTRING (value_expression ,start_expression ,length_expression )
although the documentation says otherwise, from the comments posted start_expression appears to be 1 - based (not 0 indexed)
For example:
SQL: SELECT x = SUBSTRING('abcdef', 0, 3);
RESULT: x = 'ab'
and NOT x = 'abc'
Any thoughts on how I can get around this ?

Answer 1

I think it's a bug. just change your codes to r.LastName.Substring(1, 1) and it works (resulting sql will be substring(1,1)).