Hi,

It seems I`ve found a bug. Cached queries stay referenced in Domain when Transaction and Session are disposed. Even worse is that the objects used in query expression stay referenced too. So, once object is used in query, it will live forever.

I wrote minimal app to show this bug:

using System;
using System.Linq;
using Xtensive.Storage;
using Xtensive.Storage.Configuration;

namespace Project1
{
    [Serializable]
    [HierarchyRoot]
    public class MyEntity : Entity
    {
        [Field, Key]
        public int Id { get; private set; }

        [Field( Length = 100 )]
        public string Text { get; set; }
    }

    class MyClass
    {
        public static int ObjectsCount;

        public int EntityId;

        public MyClass()
        {
            ++ObjectsCount;
        }

        ~MyClass()
        {
            --ObjectsCount;
        }

        public static void DumpObjectsCount()
        {
            Console.WriteLine( "Objects count: {0}", ObjectsCount );
        }
    }

    class Program
    {
        static void Main( string[] args )
        {
            var config = DomainConfiguration.Load( "Default" );
            var domain = Domain.Build( config );

            MyClass.DumpObjectsCount();

            Console.WriteLine( "Run test..." );
            Test( domain );

            Console.WriteLine( "\r\nCollect garbage..." );
            GC.Collect();
            GC.WaitForPendingFinalizers();

            Console.WriteLine( "\r\nAnd finnaly:" );
            MyClass.DumpObjectsCount();

            if( MyClass.ObjectsCount != 0 ) {
                Console.WriteLine( "\r\nMemory leaks found!" );
            } else {
                Console.WriteLine( "\r\nMemory leaks not found!" );
            }

            Console.ReadKey();
        }

        private static void Test( Domain domain )
        {
            MyClass obj = new MyClass
            {
                EntityId = 10
            };

            MyClass.DumpObjectsCount();

            Console.WriteLine( "\r\nExecute query..." );
            using( Session.Open( domain ) ) {
                using( var transactionScope = Transaction.Open() ) {
                    int count = (from e in Query.All<MyEntity>() where e.Id == obj.EntityId select e).Count();
                    // no memory leaks:
                    //int count = (from e in Query.All<MyEntity>() where e.Id == 10 select e).Count();

                    Console.WriteLine( "Query result: {0}", count );

                    transactionScope.Complete();
                }
            }
        }
    }
}

And there is reference graph made by memory profiling tool: http://img11.imageshost.ru/imgs/100427/988dd258f2/t7b032.png

Graph is made from app snapshoot in:

Console.ReadKey();

This thread was imported from our support forum. The original discussion may contain more detailed answer. Original topic by Konstantin.