Merge branch '7.1'

Author: alex-kulakov

Orm/Xtensive.Orm/Orm/Building/Definitions/TypeDef.cs

@@ -21,7 +21,7 @@ namespace Xtensive.Orm.Building.Definitions
   /// <summary>
   /// Defines a single persistent type.
   /// </summary>
-  [DebuggerDisplay("{underlyingType}")]
+  [DebuggerDisplay("{UnderlyingType}")]
   [Serializable]
   public sealed class TypeDef : SchemaMappedNode
   {

Orm/Xtensive.Orm/Orm/Linq/TranslatorContext.cs

@@ -24,8 +24,6 @@ namespace Xtensive.Orm.Linq
 {
   internal sealed class TranslatorContext
   {
-    private readonly static System.Type TagProviderType = typeof(TagProvider);
-
     private readonly AliasGenerator resultAliasGenerator;
     private readonly AliasGenerator columnAliasGenerator;
     private readonly Dictionary<ParameterExpression, Parameter<Tuple>> tupleParameters;

Orm/Xtensive.Orm/Sql/Compiler/Internals/Nodes/ContainerNode.cs

@@ -164,7 +164,7 @@ internal override void AcceptVisitor(NodeVisitor visitor)
     internal void FlushBuffer()
     {
       if (stringBuilder.Length > 0) {
-        children.Add(new TextNode(stringBuilder.ToString()));
+        children.Add(TextNode.Create(stringBuilder.ToString()));
         lastNodeIsText = true;
         lastChar = stringBuilder[^1];
         _ = stringBuilder.Clear();

Orm/Xtensive.Orm/Sql/Compiler/Internals/Nodes/TextNode.cs

@@ -9,18 +9,29 @@ namespace Xtensive.Sql.Compiler
   [DebuggerDisplay("Text = {Text}")]
   internal class TextNode : Node
   {
+    private const string CommaString = ", ";
+    private static readonly TextNode CommaNode = new TextNode(CommaString);
+
     public readonly string Text;
 
-    internal override void AcceptVisitor(NodeVisitor visitor)
+    public static TextNode Create(string text)
     {
-      visitor.Visit(this);
+      if (text.Length < 3) {
+        text = string.Intern(text);
+        if (text == CommaString) {
+          return CommaNode;
+        }
+      }
+      return new TextNode(text);
     }
 
+    internal override void AcceptVisitor(NodeVisitor visitor) => visitor.Visit(this);
+
     // Constructor
 
     public TextNode(string text)
     {
       Text = text;
     }
   }
-}
+}