Optimize FieldExpression construction

Orm/Xtensive.Orm/Orm/Linq/Expressions/EntityExpression.cs

@@ -4,9 +4,6 @@
 // Created by: Alexis Kochetov
 // Created:    2009.05.05
 
-using System;
-using System.Linq;
-using System.Collections.Generic;
 using System.Linq.Expressions;
 using Xtensive.Orm.Model;
 using Xtensive.Orm.Linq.Expressions.Visitors;
@@ -184,26 +181,11 @@ public static EntityExpression Create(EntityFieldExpression entityFieldExpressio
           entityFieldExpression.OuterParameter, new Dictionary<Expression, Expression>());
     }
 
-    private static PersistentFieldExpression BuildNestedFieldExpression(FieldInfo nestedField, ColNum offset)
-    {
-      if (nestedField.IsPrimitive) {
-        return FieldExpression.CreateField(nestedField, offset);
-      }
-
-      if (nestedField.IsStructure) {
-        return StructureFieldExpression.CreateStructure(nestedField, offset);
-      }
-
-      if (nestedField.IsEntity) {
-        return EntityFieldExpression.CreateEntityField(nestedField, offset);
-      }
-
-      if (nestedField.IsEntitySet) {
-        return EntitySetExpression.CreateEntitySet(nestedField);
-      }
-
-      throw new NotSupportedException(string.Format(Strings.ExNestedFieldXIsNotSupported, nestedField.Attributes));
-    }
+    private static PersistentFieldExpression BuildNestedFieldExpression(FieldInfo nestedField, ColNum offset) =>
+      nestedField.IsStructure ? StructureFieldExpression.CreateStructure(nestedField, offset)
+      : nestedField.IsEntity ? EntityFieldExpression.CreateEntityField(nestedField, offset)
+      : nestedField.IsEntitySet ? EntitySetExpression.CreateEntitySet(nestedField)
+      : FieldExpression.CreateField(nestedField, offset);
 
     public override string ToString() => $"{base.ToString()} {PersistentType.Name}";
 
@@ -222,4 +204,4 @@ private EntityExpression(
       Key = key;
     }
   }
-}
+}

Orm/Xtensive.Orm/Orm/Linq/Expressions/EntityFieldExpression.cs

@@ -162,10 +162,12 @@ public static EntityFieldExpression CreateEntityField(FieldInfo entityField, Col
       var mapping = new Segment<ColNum>((ColNum) (mappingInfo.Offset + offset), mappingInfo.Length);
       var keyFields = persistentType.Key.Fields;
       var keyExpression = KeyExpression.Create(persistentType, (ColNum) (offset + mappingInfo.Offset));
-      var fields = new List<PersistentFieldExpression>(keyFields.Count + 1) { keyExpression };
+      var fields = new PersistentFieldExpression[keyFields.Count + 1];
+      fields[0] = keyExpression;
+      int i = 1;
       foreach (var field in keyFields) {
         // Do not convert to LINQ. We want to avoid a closure creation here.
-        fields.Add(BuildNestedFieldExpression(field, (ColNum) (offset + mappingInfo.Offset)));
+        fields[i++] = BuildNestedFieldExpression(field, (ColNum) (offset + mappingInfo.Offset));
       }
 
       return new EntityFieldExpression(persistentType, entityField, fields, mapping, keyExpression, null, null, false);
@@ -205,4 +207,4 @@ private EntityFieldExpression(
       Entity = entity;
     }
   }
-}
+}

Orm/Xtensive.Orm/Orm/Linq/Expressions/FieldExpression.cs

@@ -4,8 +4,6 @@
 // Created by: Alexis Kochetov
 // Created:    2009.05.05
 
-using System;
-using System.Collections.Generic;
 using System.Linq.Expressions;
 using Xtensive.Core;
 using Xtensive.Orm.Linq.Expressions.Visitors;
@@ -137,4 +135,4 @@ protected FieldExpression(
       Field = field;
     }
   }
-}
+}

Orm/Xtensive.Orm/Orm/Linq/Expressions/StructureFieldExpression.cs

@@ -17,14 +17,14 @@ namespace Xtensive.Orm.Linq.Expressions
   internal sealed class StructureFieldExpression : FieldExpression,
     IPersistentExpression
   {
-    private List<PersistentFieldExpression> fields;
+    private IReadOnlyList<PersistentFieldExpression> fields;
     public TypeInfo PersistentType { get; }
 
     public bool IsNullable => Owner != null && Owner.IsNullable;
 
     public IReadOnlyList<PersistentFieldExpression> Fields => fields;
 
-    private void SetFields(List<PersistentFieldExpression> value)
+    private void SetFields(IReadOnlyList<PersistentFieldExpression> value)
     {
       fields = value;
       foreach (var fieldExpression in fields.OfType<FieldExpression>()) {
@@ -103,10 +103,11 @@ public override StructureFieldExpression BindParameter(ParameterExpression param
 
       var result = new StructureFieldExpression(PersistentType, Field, Mapping, OuterParameter, DefaultIfEmpty);
       processedExpressions.Add(this, result);
-      var processedFields = new List<PersistentFieldExpression>(fields.Count);
+      var processedFields = new PersistentFieldExpression[fields.Count];
+      int i = 0;
       foreach (var field in fields) {
         // Do not convert to LINQ. We want to avoid a closure creation here.
-        processedFields.Add((PersistentFieldExpression) field.BindParameter(parameter, processedExpressions));
+        processedFields[i++] = (PersistentFieldExpression) field.BindParameter(parameter, processedExpressions);
       }
 
       if (Owner == null) {
@@ -127,10 +128,11 @@ public override Expression RemoveOuterParameter(Dictionary<Expression, Expressio
 
       var result = new StructureFieldExpression(PersistentType, Field, Mapping, OuterParameter, DefaultIfEmpty);
       processedExpressions.Add(this, result);
-      var processedFields = new List<PersistentFieldExpression>(fields.Count);
+      var processedFields = new PersistentFieldExpression[fields.Count];
+      int i = 0;
       foreach (var field in fields) {
         // Do not convert to LINQ. We want to avoid a closure creation here.
-        processedFields.Add((PersistentFieldExpression) field.RemoveOuterParameter(processedExpressions));
+        processedFields[i++] = (PersistentFieldExpression) field.RemoveOuterParameter(processedExpressions);
       }
 
       if (Owner == null) {
@@ -149,14 +151,9 @@ public override FieldExpression RemoveOwner()
         return this;
       }
 
-      var result = new StructureFieldExpression(PersistentType, Field, Mapping, OuterParameter, DefaultIfEmpty) {
-        fields = new List<PersistentFieldExpression>(fields.Count)
+      return new StructureFieldExpression(PersistentType, Field, Mapping, OuterParameter, DefaultIfEmpty) {
+        fields = fields.Select(o => ((FieldExpression) o).RemoveOwner()).ToArray()
       };
-      foreach (var field in fields) {
-        result.fields.Add(((FieldExpression) field).RemoveOwner());
-      }
-
-      return result;
     }
 
     public static StructureFieldExpression CreateStructure(FieldInfo structureField, ColNum offset)
@@ -213,4 +210,4 @@ private StructureFieldExpression(
       PersistentType = persistentType;
     }
   }
-}
+}