Antlr.Runtime.MismatchedTokenException using NHibernate 3.3

Question

I'm attempting to update one of our largest projects from NHibernate 2.1 to the latest version, 3.3 and am running into an issue where a query that previously worked fine now throws an Antlr.Runtime.MismatchedTokenException error.

The HQL:

select count(a.Student)
from ExpiringAccessArrangement a
and a.Student.IsAttending = 1

The two entity classes (simplified for this example):

public class Student {
    public virtual int StudentRef { get; set; }
    public virtual string Surname { get; set; }
    public virtual string Forename { get; set; }
    public virtual bool IsAttending { get; set; }
    /* other properties */
}

public class ExpiringAccessArrangement {
    public virtual Student Student { get; set; }
    public virtual DateTime DateAdded { get; set; }

    /* other properties */

    /* equality members */
}

The mappings (again, simplified for this example):

<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly="OurProduct.Model" namespace="OurProduct.Model.Core">    
    <class name="Student" table="Students">
        <id name="StudentRef" column="Student_Ref" unsaved-value="0">
            <generator class="assigned" />
        </id>
        <property name="Surname" />
        <property name="Forename" />
        <property name="IsAttending" formula="(CASE Enrolled_Code WHEN 4 THEN 1 ELSE 0 END)" />
        <!-- other properties -->
    </class>
</hibernate-mapping>

<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly="OurProduct.Model" namespace="OurProduct.Model.Core">
    <class name="ExpiringAccessArrangement" table="NonDefaultSchemaNameHere.Expiring_Access_Arrangements">
        <composite-id>
            <key-many-to-one name="Student" class="OurProduct.Model.Core.Student" column="Student_Ref" />
            <key-property name="DateAdded" column="Date_Added" />
        </composite-id>
        <!-- other properties -->
    </class>
</hibernate-mapping>

The exception being thrown is this:

Type: NHibernate.Hql.Ast.ANTLR.QuerySyntaxException
Message: Exception of type 'Antlr.Runtime.MismatchedTokenException' was thrown. near line 4, column 24
Source: NHibernate
Target site: Void ThrowQueryException()
Stack trace: 
   at NHibernate.Hql.Ast.ANTLR.ErrorCounter.ThrowQueryException()
   at NHibernate.Hql.Ast.ANTLR.HqlParseEngine.Parse()
   at NHibernate.Hql.Ast.ANTLR.ASTQueryTranslatorFactory.CreateQueryTranslators(String queryString, String collectionRole, Boolean shallow, IDictionary`2 filters, ISessionFactoryImplementor factory)
   at NHibernate.Engine.Query.HQLStringQueryPlan..ctor(String hql, Boolean shallow, IDictionary`2 enabledFilters, ISessionFactoryImplementor factory)
   at NHibernate.Engine.Query.QueryPlanCache.GetHQLQueryPlan(String queryString, Boolean shallow, IDictionary`2 enabledFilters)
   at NHibernate.Impl.AbstractSessionImpl.GetHQLQueryPlan(String query, Boolean shallow)
   at NHibernate.Impl.AbstractSessionImpl.CreateQuery(String queryString)

Maybe this is a simple thing, but all I've done, as I said above, is move to a newer version of NHibernate. To the best of my knowledge and Googling ability, this should be fine. What's wrong?

Answer 1

I've just found the answer... the query had and where it should have said where:

select count(a.Student)
from ExpiringAccessArrangement a
WHERE a.Student.IsAttending = 1

I have literally no idea why that worked, ever...!