What is schemaExport in Fluent NHibernate?

Question

I am curious to know more on how this code and what is expected when executed.

        /// <summary>
        /// Sets up NHibernate, and adds an ISessionFactory to the given
        /// container.
        /// </summary>
        private void ConfigureNHibernate(IKernel container)
        {
            // Build the NHibernate ISessionFactory object
            var sessionFactory = FluentNHibernate
                .Cfg.Fluently.Configure()
                .Database(
                    MsSqlConfiguration.MsSql2008.ConnectionString(
                        c => c.FromConnectionStringWithKey("ServicesDb")))
                .CurrentSessionContext("web")
                .Mappings(m => m.FluentMappings.AddFromAssemblyOf<SqlCommandFactory>())
                //.ExposeConfiguration(cfg => new SchemaUpdate(cfg).Execute(true, true))
                .ExposeConfiguration(cfg =>
                                         {
                                             var schemaExport = new SchemaExport(cfg);
                                             schemaExport.Drop(true, true);
                                             schemaExport.Create(true, true);
                                         })
                .BuildSessionFactory();

            // Add the ISessionFactory instance to the container
            container.Bind<ISessionFactory>().ToConstant(sessionFactory);

            // Configure a resolver method to be used for creating ISession objects
            container.Bind<ISession>().ToMethod(CreateSession);

            container.Bind<ICurrentSessionContextAdapter>().To<CurrentSessionContextAdapter>();
        }

Now i know what most of it is doing, but i am more interested to know more about this section;

.ExposeConfiguration(cfg =>
                          {
                              var schemaExport = new SchemaExport(cfg);
                              schemaExport.Drop(true, true);
                              schemaExport.Create(true, true);
                           })

Idealy i expect schemaExport.Drop(true, true); to drop the database schema and schemaExport.Create(true, true); to recreate it. Now, is SchemaExport about the Database Schemas as we know it? I ask this because when i run my application with the mentioned configurations i get an error:

There is already an object named 'AllUsers' in the database. at schemaExport.Create(true, true);

AllUsers is one of the database views i have as part of the schema

Appending Answer as requested

To fix the bug, i added SchemaAction.None(); to UserMap as seen below.

public class UserMap : VersionedClassMap<User>
{
    public UserMap()
    {
        Table("AllUsers"); //This is the database view which was causing the error
        SchemaAction.None(); // This was added to fix the porblem

        Id(x => x.UserId).CustomType<Guid>();            
        Map(x => x.Firstname).Not.Nullable();
        Map(x => x.Lastname).Not.Nullable();            
        Map(x => x.Email).Nullable();
        Map(x => x.Username).Not.Nullable();
    }
}

Answer 1

The error says that Schemaexport tries to create AllUsers two times, most probably because there is an AuxiliaryDatabase object to create the view and an Entity Mapping to use it. Set SchemaAction.None() in the AllUsers mapping.

Also:

.ExposeConfiguration(cfg =>
                      {
                          var schemaExport = new SchemaExport(cfg);
                          schemaExport.Drop(true, true);
                          schemaExport.Create(true, true);
                       })

can be shortened to

.ExposeConfiguration(cfg => new SchemaExport(cfg).Create(true, true))

because Create does always drops before creating it would duplicate the dropping as it stands.