FluenNHibernate .Formula(“…”) not work

Question

I use FluentNHibernate with AutoMapping. No custom conventions or alterations are used. Both NHibernate and FluentNHibernate assemblies are of the latest versions. Database is Sqlite3

I try to use the following entities (table per hierarchy):

public abstract class Unit
{
  public virtual int Id { get; set; }
  public virtual string Name { get; set; }
}

public class Employee : Unit
{       
  public Employee()
  {
    this.Groups = new List<Group>();
  }

  public virtual IList<Group> Groups { get; private set; }      
}

public class Group : Unit
{
  public Group ()
  {
    this.Employees = new List<Employee>();
  }

  public virtual int EmployeesCount { get; set; }

  public virtual IList<Employee> Employees { get; private set; }

}   

public class GroupAutoMappingOverride : IAutoMappingOverride<Group>
{
  public void Override (AutoMapping<Group> mapping)
  {
    mapping.Map(g => g.EmployeesCount).Formula("count(*)");
  }
}

I auto generate schema. All is fine:

create table "Unit" (
  Id  integer,
  TypeId TEXT not null, //discriminator column
  Name TEXT,
  primary key (Id)
)

create table EmployeesToGroups (
  Employee_id INTEGER not null,
  Group_id INTEGER not null
)

I checked out the auto generated mapping:

<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2">
  <class xmlns="urn:nhibernate-mapping-2.2" name="App.Models.Entities.Unit, App, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null" table="`Unit`">
    <id name="Id" type="System.Int32, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089">
      <column name="Id" />
      <generator class="identity" />
    </id>
    <discriminator type="String">
      <column name="TypeId" />
    </discriminator>
    <property name="Name" type="System.String, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089">
      <column name="Name" />
    </property>
   <subclass name="App.Models.Entities.Employee, App, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null">
      <bag access="backfield" name="Groups" table="GroupToEmployee">
        <key>
          <column name="Employee_id" />
        </key>
        <many-to-many class="App.Models.Entities.Group, App, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null">
          <column name="Group_id" />
        </many-to-many>
      </bag>      
    </subclass>
    <subclass name="App.Models.Entities.Group, App, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null">
      <bag access="backfield" inverse="true" name="Employees" table="EmployeeToGroup">
        <key>
          <column name="Group_id" />
        </key>
        <many-to-many class="App.Models.Entities.Employee, App, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null">
          <column name="Employee_id" />
        </many-to-many>
      </bag>
      <property name="EmployeesCount" type="System.Int32, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089">
        <column name="EmployeesCount" />
      </property>
    </subclass>
  </class>
</hibernate-mapping>

Hm.. No formula... and when i try to get all records from group i get an exception:

SQLite error
no such column: group0_.EmployeesCount

The generated query is wrong:

NHibernate: select group0_.Id as Id6_, group0_.Name as Name6_, **group0_.EmployeesCount** as Employee9_6_ from "Unit" group0_ where group0_.TypeId='App.Models.Entities
.Group'

What's wrong? And is it supposed to work?

Answer 1

It doesn't appear that your mapping override is being taken into account. If it was you should see something like this in the mapping file:

<property name="EmployeesCount" formula="count(*)" type="System.Int32, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" />

Have you included your mapping overrides when building the mappings like the following:

"To use overrides, you need to instruct your AutoMap instance to use them. Typically this would be done in the context of a fluent configuration setup, but I'll just illustrate with the AutoMap on it's own."

AutoMap.AssemblyOf<Person>(cfg)
  .UseOverridesFromAssemblyOf<PersonMappingOverride>();

The above was taken from http://wiki.fluentnhibernate.org/Auto_mapping#Overrides