Convert Pinner & SyncManager into structs to save allocations (#340)

* Convert `Pinner` into `struct` to save allocations

* Convert `Pinner` into `struct` to save allocations

* Dont make struct field readonly

Author: SergeiPavlov

Orm/Xtensive.Orm/Orm/Internals/PairIntegrity/SyncManager.cs

@@ -4,15 +4,13 @@
 // Created by: Dmitri Maximov
 // Created:    2008.10.08
 
-using System;
-using Xtensive.Core;
 using Xtensive.Orm.Internals;
 using Xtensive.Orm.Model;
 using Xtensive.Orm.ReferentialIntegrity;
 
 namespace Xtensive.Orm.PairIntegrity
 {
-  internal class SyncManager : SessionBound
+  internal readonly struct SyncManager(Session session)
   {
     public void ProcessRecursively(SyncContext context, RemovalContext removalContext, 
       OperationType type, AssociationInfo association, Entity owner, Entity target,
@@ -62,7 +60,7 @@ private SyncContext CreateContext(RemovalContext removalContext,
           context.Enqueue(new SyncAction(slaveActions.Break, association.Reversed, slave1, master1));
         break;
       case OperationType.Remove:
-        var currentRemovalContext = Session.RemovalProcessor.Context;
+        var currentRemovalContext = session.RemovalProcessor.Context;
         var isNotYetRemoved = currentRemovalContext==null || !currentRemovalContext.Contains(slave2);
         if ((!(association.IsLoop && master1==slave2)) && isNotYetRemoved)
           context.Enqueue(new SyncAction(slaveActions.Break, association.Reversed, slave2, master1));
@@ -92,13 +90,5 @@ private static SyncActionSet GetSyncActions(AssociationInfo association)
         throw new ArgumentOutOfRangeException("association");
       }
     }
-
-
-    // Constructors
-
-    public SyncManager(Session session)
-      : base(session)
-    {
-    }
   }
 }

Orm/Xtensive.Orm/Orm/Internals/Pinner.cs

@@ -4,9 +4,6 @@
 // Created by: Denis Krjuchkov
 // Created:    2009.12.11
 
-using System;
-using System.Collections.Generic;
-using System.Linq;
 using Xtensive.Orm.Model;
 
 namespace Xtensive.Orm.Internals
@@ -16,7 +13,7 @@ public readonly struct PinnerDisposableRemover(HashSet<EntityState> roots, Entit
     public void Dispose() => roots?.Remove(state);
   }
 
-  internal sealed class Pinner : SessionBound
+  internal struct Pinner(Session session)
   {
     private readonly HashSet<EntityState> roots = new();
 
@@ -38,8 +35,8 @@ public void Process(EntityChangeRegistry registry)
       activeRegistry = registry;
       PinAll();
 
-      PinnedItems = new EntityChangeRegistry(Session);
-      PersistableItems = new EntityChangeRegistry(Session);
+      PinnedItems = new EntityChangeRegistry(session);
+      PersistableItems = new EntityChangeRegistry(session);
 
       ProcessRegistry(PersistenceState.New);
       ProcessRegistry(PersistenceState.Modified);
@@ -130,18 +127,5 @@ private IEnumerable<EntityState> QueryRegistry(TypeInfo type)
     }
 
     #endregion
-
-    
-    // Constructors
-
-    /// <summary>
-    /// Initializes a new instance of this class.
-    /// </summary>
-    /// <param name="session"><see cref="Session"/>, to which current instance 
-    /// is bound.</param>
-    public Pinner(Session session)
-      : base(session)
-    {
-    }
   }
-}
+}

Orm/Xtensive.Orm/Orm/Session.cs

@@ -85,7 +85,7 @@ private static readonly Type
 
     private readonly bool allowSwitching;
     private readonly long identifier;
-    private readonly Pinner pinner;
+    private Pinner pinner;
 
     private int? commandTimeout;
     private volatile int isDisposing; // To prevent double-disposing
@@ -237,7 +237,7 @@ public static Func<Session> Resolver
 
     internal HandlerAccessor Handlers { get; private set; }
 
-    internal SyncManager PairSyncManager { get; private set; }
+    internal SyncManager PairSyncManager { get; }
 
     internal RemovalProcessor RemovalProcessor { get; private set; }
 
@@ -559,9 +559,9 @@ internal Session(Domain domain, StorageNode selectedStorageNode, SessionConfigur
       SystemEvents = new SessionEventAccessor(this, true);
 
       // Etc.
-      PairSyncManager = new SyncManager(this);
+      PairSyncManager = new(this);
       RemovalProcessor = new RemovalProcessor(this);
-      pinner = new Pinner(this);
+      pinner = new(this);
       Operations = new OperationRegistry(this);
       NonPairedReferencesRegistry = new(this);