Less .AsReadOnly() calls or array based ReadOnlyCollections for memory-efficiency

Author: alex-kulakov

Orm/Xtensive.Orm/Linq/ExpressionVisitor.cs

@@ -31,14 +31,27 @@ protected override ReadOnlyCollection<Expression> VisitExpressionList(ReadOnlyCo
       return isChanged ? results.AsReadOnly() : expressions;
     }
 
+    protected override IReadOnlyList<Expression> VisitExpressionList(IReadOnlyList<Expression> expressions)
+    {
+      bool isChanged = false;
+      var results = new Expression[expressions.Count];
+      for (int i = 0, n = expressions.Count; i < n; i++) {
+        var expression = expressions[i];
+        var p = Visit(expression);
+        results[i] = p;
+        isChanged |= !ReferenceEquals(expression, p);
+      }
+      return isChanged ? results : expressions;
+    }
+
     /// <summary>
     /// Visits the element initializer expression.
     /// </summary>
     /// <param name="initializer">The initializer.</param>
     /// <returns>Visit result.</returns>
     protected virtual ElementInit VisitElementInitializer(ElementInit initializer)
     {
-      ReadOnlyCollection<Expression> arguments = VisitExpressionList(initializer.Arguments);
+      var arguments = VisitExpressionList((IReadOnlyList<Expression>)initializer.Arguments);
       if (arguments!=initializer.Arguments) {
         return Expression.ElementInit(initializer.AddMethod, arguments);
       }
@@ -63,6 +76,24 @@ protected virtual ReadOnlyCollection<ElementInit> VisitElementInitializerList(Re
       return isChanged ? results.AsReadOnly() : original;
     }
 
+    /// <summary>
+    /// Visits the element initializer list.
+    /// </summary>
+    /// <param name="original">The original element initializer list.</param>
+    /// <returns>Visit result.</returns>
+    protected virtual IReadOnlyList<ElementInit> VisitElementInitializerList(IReadOnlyList<ElementInit> original)
+    {
+      var results = new ElementInit[original.Count];
+      bool isChanged = false;
+      for (int i = 0, n = original.Count; i < n; i++) {
+        var originalIntializer = original[i];
+        ElementInit p = VisitElementInitializer(originalIntializer);
+        results[i] = p;
+        isChanged |= !ReferenceEquals(originalIntializer, p);
+      }
+      return isChanged ? results : original;
+    }
+
     /// <inheritdoc/>
     protected override Expression VisitUnary(UnaryExpression u)
     {
@@ -133,7 +164,7 @@ protected override Expression VisitMemberAccess(MemberExpression m)
     protected override Expression VisitMethodCall(MethodCallExpression mc)
     {
       Expression instance = Visit(mc.Object);
-      IEnumerable<Expression> arguments = VisitExpressionList(mc.Arguments);
+      IEnumerable<Expression> arguments = VisitExpressionList((IReadOnlyList<Expression>) mc.Arguments);
       if ((instance==mc.Object) && (arguments==mc.Arguments))
         return mc;
       return Expression.Call(instance, mc.Method, arguments);
@@ -164,7 +195,7 @@ protected override Expression VisitLambda(LambdaExpression l)
     /// <inheritdoc/>
     protected override Expression VisitNew(NewExpression n)
     {
-      IEnumerable<Expression> arguments = VisitExpressionList(n.Arguments);
+      IEnumerable<Expression> arguments = VisitExpressionList((IReadOnlyList<Expression>) n.Arguments);
       if (arguments==n.Arguments)
         return n;
       if (n.Members!=null)
@@ -176,7 +207,7 @@ protected override Expression VisitNew(NewExpression n)
     protected override Expression VisitMemberInit(MemberInitExpression mi)
     {
       var newExpression = (NewExpression) VisitNew(mi.NewExpression);
-      IEnumerable<MemberBinding> bindings = VisitBindingList(mi.Bindings);
+      IEnumerable<MemberBinding> bindings = VisitBindingList((IReadOnlyList<MemberBinding>)mi.Bindings);
       if ((newExpression==mi.NewExpression) && (bindings==mi.Bindings))
         return mi;
       return Expression.MemberInit(newExpression, bindings);
@@ -186,7 +217,7 @@ protected override Expression VisitMemberInit(MemberInitExpression mi)
     protected override Expression VisitListInit(ListInitExpression li)
     {
       var newExpression = (NewExpression) VisitNew(li.NewExpression);
-      IEnumerable<ElementInit> initializers = VisitElementInitializerList(li.Initializers);
+      IEnumerable<ElementInit> initializers = VisitElementInitializerList((IReadOnlyList<ElementInit>) li.Initializers);
       if ((newExpression==li.NewExpression) && (initializers==li.Initializers))
         return li;
       return Expression.ListInit(newExpression, initializers);
@@ -195,7 +226,7 @@ protected override Expression VisitListInit(ListInitExpression li)
     /// <inheritdoc/>
     protected override Expression VisitNewArray(NewArrayExpression na)
     {
-      IEnumerable<Expression> initializers = VisitExpressionList(na.Expressions);
+      IEnumerable<Expression> initializers = VisitExpressionList((IReadOnlyList<Expression>) na.Expressions);
       if (initializers==na.Expressions)
         return na;
       if (na.NodeType==ExpressionType.NewArrayInit)
@@ -206,7 +237,7 @@ protected override Expression VisitNewArray(NewArrayExpression na)
     /// <inheritdoc/>
     protected override Expression VisitInvocation(InvocationExpression i)
     {
-      IEnumerable<Expression> arguments = VisitExpressionList(i.Arguments);
+      IEnumerable<Expression> arguments = VisitExpressionList((IReadOnlyList<Expression>) i.Arguments);
       Expression expression = Visit(i.Expression);
       if ((arguments==i.Arguments) && (expression==i.Expression))
         return i;
@@ -241,7 +272,7 @@ protected virtual MemberBinding VisitBinding(MemberBinding binding)
     /// <returns>Visit result.</returns>
     protected virtual MemberMemberBinding VisitMemberMemberBinding(MemberMemberBinding binding)
     {
-      IEnumerable<MemberBinding> bindings = VisitBindingList(binding.Bindings);
+      IEnumerable<MemberBinding> bindings = VisitBindingList((IReadOnlyList<MemberBinding>) binding.Bindings);
       if (bindings!=binding.Bindings) {
         return Expression.MemberBind(binding.Member, bindings);
       }
@@ -255,7 +286,7 @@ protected virtual MemberMemberBinding VisitMemberMemberBinding(MemberMemberBindi
     /// <returns>Visit result.</returns>
     protected virtual ReadOnlyCollection<MemberBinding> VisitBindingList(ReadOnlyCollection<MemberBinding> original)
     {
-      var results = new List<MemberBinding>();
+      var results = new List<MemberBinding>(original.Count);
       bool isChanged = false;
       for (int i = 0, n = original.Count; i < n; i++) {
         var originalBinding = original[i];
@@ -266,9 +297,27 @@ protected virtual ReadOnlyCollection<MemberBinding> VisitBindingList(ReadOnlyCol
       return isChanged ? results.AsReadOnly() : original;
     }
 
+    /// <summary>
+    /// Visits the binding list.
+    /// </summary>
+    /// <param name="original">The original binding list.</param>
+    /// <returns>Visit result.</returns>
+    protected virtual IReadOnlyList<MemberBinding> VisitBindingList(IReadOnlyList<MemberBinding> original)
+    {
+      var results = new MemberBinding[original.Count];
+      bool isChanged = false;
+      for (int i = 0, n = original.Count; i < n; i++) {
+        var originalBinding = original[i];
+        MemberBinding p = VisitBinding(originalBinding);
+        results[i] = p;
+        isChanged |= !ReferenceEquals(originalBinding, p);
+      }
+      return isChanged ? results : original;
+    }
+
     protected virtual MemberListBinding VisitMemberListBinding(MemberListBinding binding)
     {
-      IEnumerable<ElementInit> initializers = VisitElementInitializerList(binding.Initializers);
+      IEnumerable<ElementInit> initializers = VisitElementInitializerList((IReadOnlyList<ElementInit>) binding.Initializers);
       if (initializers!=binding.Initializers)
         return Expression.ListBind(binding.Member, initializers);
       return binding;

Orm/Xtensive.Orm/Linq/ExpressionVisitor{TResult}.cs

@@ -152,6 +152,20 @@ protected virtual ReadOnlyCollection<TResult> VisitExpressionList(ReadOnlyCollec
       return results.AsReadOnly();
     }
 
+    /// <summary>
+    /// Visits the expression list.
+    /// </summary>
+    /// <param name="expressions">The expression list.</param>
+    /// <returns>Visit result.</returns>
+    protected virtual IReadOnlyList<TResult> VisitExpressionList(IReadOnlyList<Expression> expressions)
+    {
+      var results = new TResult[expressions.Count];
+      for (int i = 0, n = expressions.Count; i < n; i++) {
+        results[i] = Visit(expressions[i]);
+      }
+      return results;
+    }
+
     /// <summary>
     /// Visits the unknown expression.
     /// </summary>

Orm/Xtensive.Orm/Linq/ExpressionWriter.cs

@@ -6,6 +6,7 @@
 
 using System;
 using System.Collections;
+using System.Collections.Generic;
 using System.Diagnostics;
 using System.IO;
 using System.Linq;
@@ -442,6 +443,20 @@ protected override System.Collections.ObjectModel.ReadOnlyCollection<ElementInit
       return original;
     }
 
+    /// <inheritdoc/>
+    protected override IReadOnlyList<ElementInit> VisitElementInitializerList(IReadOnlyList<ElementInit> original)
+    {
+      for (int i = 0, n = original.Count; i < n; i++) {
+        VisitElementInitializer(original[i]);
+        if (i < n - 1) {
+          Write(",");
+          WriteLine(IndentType.Same);
+        }
+      }
+
+      return original;
+    }
+
     /// <inheritdoc/>
     protected override System.Collections.ObjectModel.ReadOnlyCollection<Expression> VisitExpressionList(
       System.Collections.ObjectModel.ReadOnlyCollection<Expression> expressions)
@@ -457,6 +472,20 @@ protected override System.Collections.ObjectModel.ReadOnlyCollection<Expression>
       return expressions;
     }
 
+    /// <inheritdoc/>
+    protected override IReadOnlyList<Expression> VisitExpressionList(IReadOnlyList<Expression> expressions)
+    {
+      for (int i = 0, n = expressions.Count; i < n; i++) {
+        Visit(expressions[i]);
+        if (i < n - 1) {
+          Write(",");
+          WriteLine(IndentType.Same);
+        }
+      }
+
+      return expressions;
+    }
+
     /// <inheritdoc/>
     protected override InvocationExpression VisitInvocation(InvocationExpression i)
     {
@@ -576,7 +605,7 @@ protected override MethodCallExpression VisitMethodCall(MethodCallExpression mc)
         if (mc.Method.GetAttributes<ExtensionAttribute>(AttributeSearchOptions.InheritNone).Count > 0) {
           // A special case: extension method
           Visit(mc.Arguments[0]);
-          arguments = new System.Collections.ObjectModel.ReadOnlyCollection<Expression>(mc.Arguments.Skip(1).ToList());
+          arguments = new System.Collections.ObjectModel.ReadOnlyCollection<Expression>(mc.Arguments.Skip(1).ToList(mc.Arguments.Count - 1));
         }
         else {
           Write(GetTypeName(mc.Method.DeclaringType));

Orm/Xtensive.Orm/Orm/Configuration/LoggingConfiguration.cs

@@ -43,12 +43,14 @@ public IList<LogConfiguration> Logs {
 
     public override void Lock(bool recursive)
     {
-      if (logs is List<LogConfiguration>nativeList) {
-        logs = nativeList.AsReadOnly();
-      }
-      else {
-        logs = logs.ToList().AsReadOnly();
-      }
+#if NET8_0_OR_GREATER
+      logs = logs.AsReadOnly();
+#else
+      logs = logs switch {
+        List<LogConfiguration> nativeList1 => nativeList1.AsReadOnly(),
+        _ => logs.ToList().AsReadOnly()
+      };
+#endif
       base.Lock(recursive);
 
       foreach (var log in logs) {

Orm/Xtensive.Orm/Orm/Internals/Prefetch/Nodes/IHasNestedNodes.cs

@@ -11,10 +11,10 @@ namespace Xtensive.Orm.Internals.Prefetch
 {
   internal interface IHasNestedNodes
   {
-    ReadOnlyCollection<BaseFieldNode> NestedNodes { get; }
+    IReadOnlyList<BaseFieldNode> NestedNodes { get; }
 
-    IReadOnlyCollection<Key> ExtractKeys(object target);
+    IReadOnlyList<Key> ExtractKeys(object target);
 
-    IHasNestedNodes ReplaceNestedNodes(ReadOnlyCollection<BaseFieldNode> nestedNodes);
+    IHasNestedNodes ReplaceNestedNodes(IReadOnlyList<BaseFieldNode> nestedNodes);
   }
 }

Orm/Xtensive.Orm/Orm/Internals/Prefetch/Nodes/KeyExtractorNode.cs

@@ -13,21 +13,21 @@ namespace Xtensive.Orm.Internals.Prefetch
 {
   internal class KeyExtractorNode<T> : Node, IHasNestedNodes
   {
-    public Func<T, IReadOnlyCollection<Key>> KeyExtractor { get; }
+    public Func<T, IReadOnlyList<Key>> KeyExtractor { get; }
 
-    public ReadOnlyCollection<BaseFieldNode> NestedNodes { get; }
+    public IReadOnlyList<BaseFieldNode> NestedNodes { get; }
 
-    IReadOnlyCollection<Key> IHasNestedNodes.ExtractKeys(object target)
+    IReadOnlyList<Key> IHasNestedNodes.ExtractKeys(object target)
     {
       return ExtractKeys((T) target);
     }
 
-    public IReadOnlyCollection<Key> ExtractKeys(T target)
+    public IReadOnlyList<Key> ExtractKeys(T target)
     {
       return KeyExtractor.Invoke(target);
     }
 
-    public IHasNestedNodes ReplaceNestedNodes(ReadOnlyCollection<BaseFieldNode> nestedNodes)
+    public IHasNestedNodes ReplaceNestedNodes(IReadOnlyList<BaseFieldNode> nestedNodes)
     {
       return new KeyExtractorNode<T>(KeyExtractor, nestedNodes);
     }
@@ -42,7 +42,7 @@ protected override string GetDescription()
       return $"KeyExtraction<{typeof(T).Name}>";
     }
 
-    public KeyExtractorNode(Func<T, IReadOnlyCollection<Key>> extractor, ReadOnlyCollection<BaseFieldNode> nestedNodes)
+    public KeyExtractorNode(Func<T, IReadOnlyList<Key>> extractor, IReadOnlyList<BaseFieldNode> nestedNodes)
       : base("*")
     {
       ArgumentValidator.EnsureArgumentNotNull(extractor, nameof(extractor));

Orm/Xtensive.Orm/Orm/Internals/Prefetch/Nodes/NodeAggregator.cs

@@ -18,15 +18,14 @@ public static IList<KeyExtractorNode<T>> Aggregate(IEnumerable<KeyExtractorNode<
       var result = source
         .GroupBy(ken => ken.Path, (path, @group) => 
           (Node) @group.First().ReplaceNestedNodes(
-            new ReadOnlyCollection<BaseFieldNode>(
-              @group.SelectMany(ken => ken.NestedNodes).ToList())))
+              @group.SelectMany(ken => ken.NestedNodes).ToList()))
         .Select(aggregator.Visit)
         .Cast<KeyExtractorNode<T>>()
         .ToList();
       return result;
     }
 
-    public override ReadOnlyCollection<BaseFieldNode> VisitNodeList(ReadOnlyCollection<BaseFieldNode> nodes)
+    public override IReadOnlyList<BaseFieldNode> VisitNodeList(IReadOnlyList<BaseFieldNode> nodes)
     {
       var result = new List<BaseFieldNode>();
       foreach (var group in nodes.Where(n => n!=null).GroupBy(n => n.Path)) {
@@ -36,11 +35,11 @@ public override ReadOnlyCollection<BaseFieldNode> VisitNodeList(ReadOnlyCollecti
           result.Add(node);
         else {
           var nodeToVisit = (BaseFieldNode) container.ReplaceNestedNodes(
-            new ReadOnlyCollection<BaseFieldNode>(group.Cast<IHasNestedNodes>().SelectMany(c => c.NestedNodes).ToList()));
+            group.Cast<IHasNestedNodes>().SelectMany(c => c.NestedNodes).ToList());
           result.Add((BaseFieldNode) Visit(nodeToVisit));
         }
       }
-      return new ReadOnlyCollection<BaseFieldNode>(result);
+      return result;
     }
 
     // Constructor

Orm/Xtensive.Orm/Orm/Internals/Prefetch/Nodes/NodeBuilder.cs

@@ -1,4 +1,4 @@
-// Copyright (C) 2012-2020 Xtensive LLC.
+// Copyright (C) 2012-2020 Xtensive LLC.
 // This code is distributed under MIT license terms.
 // See the License.txt file in the project root for more information.
 // Created by: Denis Krjuchkov
@@ -34,7 +34,7 @@ public static KeyExtractorNode<T> Build<T, TValue>(DomainModel model, Expression
       return new KeyExtractorNode<T>(GetExtractor<T>(), nestedNodes);
     }
 
-    private static Func<T, IReadOnlyCollection<Key>> GetExtractor<T>()
+    private static Func<T, IReadOnlyList<Key>> GetExtractor<T>()
     {
       return target => new[] {((IEntity) target).Key};
     }

Orm/Xtensive.Orm/Orm/Internals/Prefetch/Nodes/NodeVisitor.cs

@@ -4,7 +4,7 @@
 // Created by: Alexis Kochetov
 // Created:    2011.01.14
 
-using System.Collections.ObjectModel;
+using System.Collections.Generic;
 
 namespace Xtensive.Orm.Internals.Prefetch
 {
@@ -17,7 +17,7 @@ public virtual Node Visit(Node node)
       return node.Accept(this);
     }
 
-    public virtual ReadOnlyCollection<BaseFieldNode> VisitNodeList(ReadOnlyCollection<BaseFieldNode> nodes)
+    public virtual IReadOnlyList<BaseFieldNode> VisitNodeList(IReadOnlyList<BaseFieldNode> nodes)
     {
       BaseFieldNode[] list = null;
       var index = 0;
@@ -37,7 +37,7 @@ public virtual ReadOnlyCollection<BaseFieldNode> VisitNodeList(ReadOnlyCollectio
       }
       return list==null
         ? nodes
-        : new ReadOnlyCollection<BaseFieldNode>(list);
+        : list;
     }
 
     public virtual Node VisitKeyExtractorNode<T>(KeyExtractorNode<T> keyExtractorNode)