Generating Wrong Columns on Queries

Question

We are having an intermittent problem with NHibernate where it will occasionally generate a query with a wrong column on the SQL. If we restart the application the problem ceases to happen (sometimes it requires more than one restart). When the problem occurs, during the lifetime of that process, it always produces the wrong SQL for the affected entity. It´s not always the same affected entity.

It´s an ASP.NET application where the SessionFactory is created during the Application_Start event. All the configuration and mapping are done by code.

We don´t have any more ideas how to test or debug the application, and I´m starting to assume there´s some bug in NHibernate, since the application fixes itself upon restart. Any ideas/tips will be much appreciated!

Here´s an example:

Entity

namespace Example.Clinicas
{
    public partial class Clinica : Entidade   // Abstract base class that has a property Handle
    {
        public virtual string Ddd { get; set; }
        public virtual string Ddd2 { get; set; }
        public virtual long? Duracao { get; set; }
        public virtual string Numero { get; set; }
        public virtual string Numero2 { get; set; }
        public virtual string Prefixo { get; set; }
        public virtual string Prefixo2 { get; set; }
        public virtual long? HandlePrestador { get; set; }
        public virtual Example.Prestadores.Prestador Prestador { get; set; }
    }
}

Mapping

namespace Example.Clinicas.Mappings
{
    public class ClinicaMapping : ClassMapping<Clinica>
    {
        public ClinicaMapping() 
        {
            Table("CLI_CLINICA");

            Id(x => x.Handle, map => 
            {
                map.Column("HANDLE");
                map.Generator(Generators.Sequence, g => g.Params(new { sequence = "SEQ_AUTO1816" }));
            });
            Property(x => x.Ddd, map => map.Column( c=> 
            {
                c.Name("DDD1");
                c.Length(4);
            }));
            Property(x => x.Ddd2, map => map.Column( c=> 
            {
                c.Name("DDD2");
                c.Length(4);
            }));
            Property(x => x.Duracao, map => map.Column("INTERVALOAGENDA"));
            Property(x => x.Numero, map => map.Column( c=> 
            {
                c.Name("NUMERO1");
                c.Length(5);
            }));
            Property(x => x.Numero2, map => map.Column( c=> 
            {
                c.Name("NUMERO2");
                c.Length(5);
            }));
            Property(x => x.Prefixo, map => map.Column( c=> 
            {
                c.Name("PREFIXO1");
                c.Length(5);
            }));
            Property(x => x.Prefixo2, map => map.Column( c=> 
            {
                c.Name("PREFIXO2");
                c.Length(5);
            }));
            Property(x => x.HandlePrestador, map => map.Column("PRESTADOR"));
            ManyToOne(x => x.Prestador, map => 
            { 
                map.Column("PRESTADOR");
                map.Insert(false);
                map.Update(false);
            });
        }
    }
}

Command

Session.Query<Clinica>().FirstOrDefault();

Generated SQL

select HANDLE489_,
       DDD2_489_,
       DDD3_489_,
       INTERVAL4_489_,
       NUMERO5_489_,
       NUMERO6_489_,
       PREFIXO7_489_,
       FATURADE8_489_,
       PRESTADOR489_
  from (select clinica0_.HANDLE               as HANDLE489_,
               clinica0_.DDD1                 as DDD2_489_,
               clinica0_.DDD2                 as DDD3_489_,
               clinica0_.INTERVALOAGENDA      as INTERVAL4_489_,
               clinica0_.NUMERO1              as NUMERO5_489_,
               clinica0_.NUMERO2              as NUMERO6_489_,
               clinica0_.PREFIXO1             as PREFIXO7_489_,
               clinica0_.FATURADEPARCELAMENTO as FATURADE8_489_,
               clinica0_.PRESTADOR            as PRESTADOR489_
          from CLI_CLINICA clinica0_)
 where rownum <= 1

Exception

ORA-00904: "CLINICA0_"."FATURADEPARCELAMENTO": invalid identifier

Interesting Observations:

• It is more likely to affect bigger entities (that has a higher number of properties), but also affects smaller entities occasionally;
• The generated SQL always have the same number of columns as mapped properties;
• The columns on the SQL are in the same order as the mapped properties on the mapping class;
• The wrong column will replace an existing one;
• The wrong column is a valid column in a different mapped entity;
• There is no relationship between the affected entity and the one that has the wrong column;

Other Details:

• .NET Version: 4.0
• NHibernate Version: 3.3.3.400
• Mapping by Code: NHibernate.Mapping.ByCode
• Configuration by Code: NHibernate.Cfg

Load Mappings

var mapper = new ModelMapper();

foreach (var assembly in resolver.GetAssemblies()) // resolver is a class that gets all the assemblies for the current application
    mapper.AddMappings(assembly.GetExportedTypes());

var mapping = mapper.CompileMappingForAllExplicitlyAddedEntities();

return mapping;

SessionFactory Configuration

var configure = new Configuration();
configure.DataBaseIntegration(x =>
                                  {
                                      x.Dialect<Oracle10gDialect>();  // Custom class
                                      x.ConnectionString = ConnectionString;
                                      x.BatchSize = 100;
                                      x.Driver<OracleMultiQueryDataClientDriver>();  // Custom class
                                      x.MaximumDepthOfOuterJoinFetching = 10;
                                      x.Timeout = 250;
                                      x.PrepareCommands = true;
                                      x.HqlToSqlSubstitutions = "true 'S', false 'N', yes 'S', no 'N'";
                                      x.LogFormattedSql = true;
                                      x.LogSqlInConsole = true;
                                      x.AutoCommentSql = true;
                                      x.IsolationLevel = IsolationLevel.ReadCommitted;
                                      x.ConnectionProvider<ConnectionProvider>();  // Custom class
                                  });
configure.Properties.Add(new KeyValuePair<string, string>("hibernate.command_timeout", "250"));
configure.Proxy(x => x.ProxyFactoryFactory<NHibernate.Bytecode.DefaultProxyFactoryFactory>());
configure.LinqToHqlGeneratorsRegistry<LinqToHqlGeneratorsRegistry>();
configure.CurrentSessionContext<NHibernate.Context.WebSessionContext>();
var mapping = GetMappings(); // Method showed above
mapping.autoimport = false;
configure.AddMapping(mapping);
var listener = new AuditEventListener();
configure.EventListeners.PostInsertEventListeners = new IPostInsertEventListener[] { listener };
configure.EventListeners.PostUpdateEventListeners = new IPostUpdateEventListener[] { listener };
configure.SessionFactory().GenerateStatistics();
return configure;

Answer 1

I asked the same question on the NHibernate Users Google Groups forum, and someone thinks they have worked out the root cause (and have also proposed a solution):

https://groups.google.com/forum/#!topic/nhusers/BZoBoyWQEvs

The problem code is in PropertyPath.Equals(PropertyPath) which attempts to determine equality by only using the hash code. This works fine for smaller code bases as the default Object.GetHashCode() returns a sequential object index. However, after garbage collection, these indices get reused as finalized objects are removed and new objects are created...which results in more than one object getting the same hashcode...Once garbage collection kicks in, property paths have a chance to share the same hashcode which means they will ultimately mix up their customizers for the colliding properties, thus the wrong column names...

If you want to fix this the bug, you can patch the NH source code:

If you have your own copy of the NH source, you can fix the bug by changing NHibernate/Mapping/ByCode/PropertyPath.cs line #66 from:

return hashCode == other.GetHashCode();

To:

return hashCode == other.GetHashCode() && ToString() == other.ToString();

Please check out the Google Group for full details of the issue.

Answer 2

it looks like the "creditcard payments" FATURADEPARCELAMENTO is a property on your "lender" object PRESTADOR, if this is the case it needs to be a reference and NOT a property in the mapping. Hope that helps or at least gets you pointed in the correct direction

the reference would take the place of your line Property(x => x.HandlePrestador, map => map.Column("PRESTADOR")); and would be something close to References(x => x.HandlePrestador)