Improve performance of EntityExpression class

Author: AlexUstinov

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

@@ -19,94 +19,115 @@ internal class EntityExpression : ParameterizedExpression,
   {
     private List<PersistentFieldExpression> fields;
 
-    public TypeInfo PersistentType { get; private set; }
+    public TypeInfo PersistentType { get; }
 
-    public KeyExpression Key { get; private set; }
+    public KeyExpression Key { get; }
 
     public List<PersistentFieldExpression> Fields
     {
-      get { return fields; }
-      private set
-      {
+      get => fields;
+      private set {
         fields = value;
-        var fieldExpressions = fields.OfType<FieldExpression>();
-        foreach (var fieldExpression in fieldExpressions)
+        foreach (var fieldExpression in fields.OfType<FieldExpression>()) {
           fieldExpression.Owner = this;
+        }
       }
     }
 
     public bool IsNullable { get; set; }
 
     public Expression Remap(int offset, Dictionary<Expression, Expression> processedExpressions)
     {
-      if (!CanRemap)
+      if (!CanRemap) {
         return this;
-      Expression value;
-      if (processedExpressions.TryGetValue(this, out value))
+      }
+
+      if (processedExpressions.TryGetValue(this, out var value)) {
         return value;
+      }
 
       var keyExpression = (KeyExpression) Key.Remap(offset, processedExpressions);
       var result = new EntityExpression(PersistentType, keyExpression, OuterParameter, DefaultIfEmpty);
       processedExpressions.Add(this, result);
       result.IsNullable = IsNullable;
-      result.Fields = Fields
-        .Select(f => f.Remap(offset, processedExpressions))
-        .Cast<PersistentFieldExpression>()
-        .ToList();
+      var processedFields = new List<PersistentFieldExpression>(fields.Count);
+      foreach (var field in fields) {
+        // Do not convert to LINQ. We want to avoid a closure creation here.
+        processedFields.Add((PersistentFieldExpression) field.Remap(offset, processedExpressions));
+      }
+
+      result.Fields = processedFields;
       return result;
     }
 
     public Expression Remap(int[] map, Dictionary<Expression, Expression> processedExpressions)
     {
-      if (!CanRemap)
+      if (!CanRemap) {
         return this;
-      Expression value;
-      if (processedExpressions.TryGetValue(this, out value))
+      }
+
+      if (processedExpressions.TryGetValue(this, out var value)) {
         return value;
+      }
 
       var keyExpression = (KeyExpression) Key.Remap(map, processedExpressions);
-      if (keyExpression==null)
+      if (keyExpression==null) {
         return null;
+      }
+
       var result = new EntityExpression(PersistentType, keyExpression, OuterParameter, DefaultIfEmpty);
       processedExpressions.Add(this, result);
       result.IsNullable = IsNullable;
-      result.Fields = Fields
-        .Select(f => f.Remap(map, processedExpressions))
-        .Where(f => f!=null)
-        .Cast<PersistentFieldExpression>()
-        .ToList();
+      var processedFields = new List<PersistentFieldExpression>(fields.Count);
+      foreach (var field in fields) {
+        // Do not convert to LINQ. We want to avoid a closure creation here.
+        var mappedField = (PersistentFieldExpression) field.Remap(map, processedExpressions);
+        if (mappedField == null) {
+          continue;
+        }
+
+        processedFields.Add(mappedField);
+      }
+
+      result.Fields = processedFields;
       return result;
     }
 
     public Expression BindParameter(ParameterExpression parameter, Dictionary<Expression, Expression> processedExpressions)
     {
-      Expression value;
-      if (processedExpressions.TryGetValue(this, out value))
+      if (processedExpressions.TryGetValue(this, out var value)) {
         return value;
+      }
 
       var keyExpression = (KeyExpression) Key.BindParameter(parameter, processedExpressions);
       var result = new EntityExpression(PersistentType, keyExpression, parameter, DefaultIfEmpty);
       processedExpressions.Add(this, result);
-      result.Fields = Fields
-        .Select(f => f.BindParameter(parameter, processedExpressions))
-        .Cast<PersistentFieldExpression>()
-        .ToList();
+      var processedFields = new List<PersistentFieldExpression>(fields.Count);
+      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));
+      }
+
+      result.Fields = processedFields;
       return result;
     }
 
     public Expression RemoveOuterParameter(Dictionary<Expression, Expression> processedExpressions)
     {
-      Expression value;
-      if (processedExpressions.TryGetValue(this, out value))
+      if (processedExpressions.TryGetValue(this, out var value)) {
         return value;
+      }
 
       var keyExpression = (KeyExpression) Key.RemoveOuterParameter(processedExpressions);
       var result = new EntityExpression(PersistentType, keyExpression, null, DefaultIfEmpty);
       processedExpressions.Add(this, result);
-      result.Fields = Fields
-        .Select(f => f.RemoveOuterParameter(processedExpressions))
-        .Cast<PersistentFieldExpression>()
-        .ToList();
+      var processedFields = new List<PersistentFieldExpression>(fields.Count);
+      foreach (var field in fields) {
+        // Do not convert to LINQ. We want to avoid a closure creation here.
+        processedFields.Add((PersistentFieldExpression) field.RemoveOuterParameter(processedExpressions));
+      }
+
+      result.Fields = processedFields;
       return result;
     }
 
@@ -127,41 +148,54 @@ public static void Fill(EntityExpression entityExpression, int offset)
 
     public static EntityExpression Create(TypeInfo typeInfo, int offset, bool keyFieldsOnly)
     {
-      if (!typeInfo.IsEntity && !typeInfo.IsInterface)
-        throw new ArgumentException(string.Format(Strings.ExPersistentTypeXIsNotEntityOrPersistentInterface, typeInfo.Name), "typeInfo");
-      var fields = new List<PersistentFieldExpression>();
+      if (!typeInfo.IsEntity && !typeInfo.IsInterface) {
+        throw new ArgumentException(
+          string.Format(Strings.ExPersistentTypeXIsNotEntityOrPersistentInterface, typeInfo.Name), nameof(typeInfo));
+      }
+
       var keyExpression = KeyExpression.Create(typeInfo, offset);
-      fields.Add(keyExpression);
+
+      List<PersistentFieldExpression> fields;
       var result = new EntityExpression(typeInfo, keyExpression, null, false);
       if (keyFieldsOnly) {
+        fields = new List<PersistentFieldExpression>(keyExpression.KeyFields.Count + 1) {keyExpression};
         // Add key fields to field collection
-        var keyFieldClones = keyExpression
-          .KeyFields
-          .Select(kf=>FieldExpression.CreateField(kf.Field, offset))
-          .Cast<PersistentFieldExpression>();
-        fields.AddRange(keyFieldClones);
-      }
-      else
-        foreach (var nestedField in typeInfo.Fields)
+        foreach (var keyField in keyExpression.KeyFields) {
+          // Do not convert to LINQ. We want to avoid a closure creation here.
+          fields.Add(FieldExpression.CreateField(keyField.Field, offset));
+        }
+      }
+      else {
+        fields = new List<PersistentFieldExpression>(typeInfo.Fields.Count + 1) {keyExpression};
+        foreach (var nestedField in typeInfo.Fields) {
+          // Do not convert to LINQ. We want to avoid a closure creation here.
           fields.Add(BuildNestedFieldExpression(nestedField, offset));
+        }
+      }
+
       result.Fields = fields;
       return result;
     }
 
     public static EntityExpression Create(EntityFieldExpression entityFieldExpression, int offset)
     {
       var typeInfo = entityFieldExpression.PersistentType;
-      var fields = new List<PersistentFieldExpression>();
       var keyExpression = KeyExpression.Create(typeInfo, offset);
-      fields.Add(keyExpression);
-      foreach (var nestedField in typeInfo.Fields)
-          fields.Add(BuildNestedFieldExpression(nestedField, offset));
+      var fields = new List<PersistentFieldExpression>(typeInfo.Fields.Count + 1) {keyExpression};
+      foreach (var nestedField in typeInfo.Fields) {
+        // Do not convert to LINQ. We want to avoid a closure creation here.
+        fields.Add(BuildNestedFieldExpression(nestedField, offset));
+      }
+
       var result = new EntityExpression(typeInfo, keyExpression, null, entityFieldExpression.DefaultIfEmpty) {
         Fields = fields
       };
-      if (entityFieldExpression.OuterParameter==null)
+      if (entityFieldExpression.OuterParameter == null) {
         return result;
-      return (EntityExpression) result.BindParameter(entityFieldExpression.OuterParameter, new Dictionary<Expression, Expression>());
+      }
+
+      return (EntityExpression) result.BindParameter(
+        entityFieldExpression.OuterParameter, new Dictionary<Expression, Expression>());
     }
 
     private static PersistentFieldExpression BuildNestedFieldExpression(FieldInfo nestedField, int offset)
@@ -177,11 +211,7 @@ private static PersistentFieldExpression BuildNestedFieldExpression(FieldInfo ne
       throw new NotSupportedException(string.Format(Strings.ExNestedFieldXIsNotSupported, nestedField.Attributes));
     }
 
-    public override string ToString()
-    {
-      return string.Format("{0} {1}", base.ToString(), PersistentType.Name);
-    }
-
+    public override string ToString() => $"{base.ToString()} {PersistentType.Name}";
 
     // Constructors