Recognition error occurs using System.Linq.Queryable.Contains

[dbakuntsev]

Background

While chasing down another NHibernate-related error, I came across this. This was working in 4.x (verified with 4.0.4.4000).

Description

Typically, when handling IQueryable<T> instances, the expectation is that invoking Contains(T) will yield a database query that is equivalent of an efficient EXISTS SQL statement. As of 5.3.3, however, the following exception is generated by the sample source code below:

NHibernate.Hql.Ast.ANTLR.QuerySyntaxException: A recognition error occurred. [.Contains[UserQuery+Video, query_wpqaxa, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null](NHibernate.Linq.NhQueryable`1[UserQuery+Video], p1<VideoProxy>, )] ---> Antlr.Runtime.NoViableAltException: A recognition error occurred.
   at NHibernate.Hql.Ast.ANTLR.HqlSqlWalker.statement()
   --- End of inner exception stack trace ---
   at NHibernate.Hql.Ast.ANTLR.ErrorCounter.ThrowQueryException()
   at NHibernate.Hql.Ast.ANTLR.HqlSqlTranslator.Translate()
   at NHibernate.Hql.Ast.ANTLR.QueryTranslatorImpl.Analyze(String collectionRole)
   at NHibernate.Hql.Ast.ANTLR.QueryTranslatorImpl.DoCompile(IDictionary`2 replacements, Boolean shallow, String collectionRole)
   at NHibernate.Hql.Ast.ANTLR.ASTQueryTranslatorFactory.CreateQueryTranslators(IQueryExpression queryExpression, IASTNode ast, String queryIdentifier, String collectionRole, Boolean shallow, IDictionary`2 filters, ISessionFactoryImplementor factory)
   at NHibernate.Hql.Ast.ANTLR.ASTQueryTranslatorFactory.CreateQueryTranslators(IQueryExpression queryExpression, String collectionRole, Boolean shallow, IDictionary`2 filters, ISessionFactoryImplementor factory)
   at NHibernate.Engine.Query.QueryPlanCache.GetHQLQueryPlan(IQueryExpression queryExpression, Boolean shallow, IDictionary`2 enabledFilters)
   at NHibernate.Impl.AbstractSessionImpl.GetHQLQueryPlan(IQueryExpression queryExpression, Boolean shallow)
   at NHibernate.Impl.AbstractSessionImpl.CreateQuery(IQueryExpression queryExpression)
   at NHibernate.Linq.DefaultQueryProvider.PrepareQuery(Expression expression, IQuery& query)
   at NHibernate.Linq.DefaultQueryProvider.Execute(Expression expression)
   at NHibernate.Linq.DefaultQueryProvider.Execute[TResult](Expression expression)
   at System.Linq.Queryable.Contains[TSource](IQueryable`1 source, TSource item)

Sample Source Code

void Main()
{
    using (var sessionFactory = ConfigureNHibernate().BuildSessionFactory())
    using (var session = sessionFactory.OpenSession())
    {
        var subtitle = session.Get<Subtitle>(1);

        // *** The exception occurs here, regardless of whether subtitle?.Video is null or not.
        if (!session.Query<Video>().Contains(subtitle?.Video))
            Console.WriteLine("error");
        else
            Console.WriteLine("OK");
    }
}

public interface IEntity
{
}

public class Video : IEntity
{
    public virtual int Id { get; set; }
    public virtual string Title { get; set; }
    public virtual IList<Subtitle> Subtitles { get; set; }
}

public class Subtitle : IEntity
{
    public virtual int Id { get; set; }
    public virtual string Language { get; set; }
    public virtual Video Video { get; set; }
}

bool IsEntity(Type t) => typeof(IEntity).IsAssignableFrom(t);

Configuration ConfigureNHibernate()
{
    var configuration = new Configuration();
    
    configuration
        .Proxy(p => p.ProxyFactoryFactory<NHibernate.Bytecode.DefaultProxyFactoryFactory>())
        .DataBaseIntegration(db =>
        {
            db.ConnectionString = null; // Provide a database connection string
            db.Dialect<NHibernate.Dialect.MsSql2008Dialect>();
        })
        .AddAssembly(this.GetType().Assembly)
        ;
    
    var mapper = new ConventionModelMapper();
    
    mapper.IsEntity((type, declared) => IsEntity(type));
    mapper.IsRootEntity((type, declared) => IsEntity(type) && !type.IsAbstract);
    
    mapper.BeforeMapClass += (modelInspector, type, classCustomizer) =>
    {
        classCustomizer.Id(c => c.Generator(Generators.Identity));
        classCustomizer.Table(type.Name + "s");
    };
    mapper.BeforeMapManyToOne += (modelInspector, propertyPath, map) =>
    {
        map.Column(propertyPath.LocalMember.GetPropertyOrFieldType().Name + "Fk");
        map.Cascade(Cascade.Persist);
    };
    mapper.BeforeMapBag += (modelInspector, propertyPath, map) =>
    {
        map.Key(keyMapper => keyMapper.Column(propertyPath.GetContainerEntity(modelInspector).Name + "Fk"));
        map.Cascade(Cascade.All);
    };
    
    var mapping = mapper.CompileMappingFor(this.GetType().Assembly.GetExportedTypes().Where(t => IsEntity(t) && !t.IsAbstract));
    configuration.AddDeserializedMapping(mapping, "mapping");
    
    return configuration;
}

Database Schema & Sample Data

CREATE TABLE [dbo].[Videos](
	[Id] [int] IDENTITY(1,1) NOT NULL,
	[Title] [nvarchar](512) NOT NULL,
 CONSTRAINT [PK_Videos] PRIMARY KEY CLUSTERED ([Id] ASC)
) ON [PRIMARY]
GO

CREATE TABLE [dbo].[Subtitles](
	[Id] [int] IDENTITY(1,1) NOT NULL,
	[VideoFk] [int] NOT NULL,
	[Language] [nvarchar](64) NOT NULL,
 CONSTRAINT [PK_Subtitles] PRIMARY KEY CLUSTERED ([Id] ASC)
) ON [PRIMARY]
GO

ALTER TABLE [dbo].[Subtitles]  WITH CHECK ADD  CONSTRAINT [FK_Subtitles_Videos] FOREIGN KEY([VideoFk])
REFERENCES [dbo].[Videos] ([Id])
ON UPDATE CASCADE
ON DELETE CASCADE
GO

ALTER TABLE [dbo].[Subtitles] CHECK CONSTRAINT [FK_Subtitles_Videos]
GO

INSERT INTO [dbo].[Videos] ([Title]) VALUES ('Sample');
INSERT INTO [dbo].[Subtitles] ([VideoFk], [Language]) VALUES (SCOPE_IDENTITY(), 'Sample');

[bahusoid]

Does it work with 5.2?

[dbakuntsev]

Does it work with 5.2?

It does not work with 5.2.7. From the looks of it, this regression may have happened between major versions 4.x and 5.x.

[bahusoid]

As a workaround you can use Any instead:

session.Query<Video>().Any(x => x == subtitle?.Video)

[orudge]

This is something I've also identified, which worked in 4.x but fails with 5.0 or later. We are able to work around it as suggested by using .Any, but it would be good if a fix can be found.

[fredericDelaporte]

We are implementing a fix for 5.3.x, but have not yet decided whether to back-port it down to 5.0.x or not, see here.

[fredericDelaporte]

Fixed by #2674