From 5ab4c5a6b5be8278a2d37a591bff5bd0a3b7069f Mon Sep 17 00:00:00 2001
From: Turnerj <git@turnerj.com>
Date: Sun, 1 Oct 2023 21:23:11 +1030
Subject: [PATCH] Improve change tracking performance for single ops

---
 .../Infrastructure/EntityEntryContainer.cs    |  8 +++-
 .../Mapping/EntityDefinition.cs               | 25 +++++++++++-
 .../EntityCollectionGetEntryBenchmark.cs      | 40 +++++++++++++++++++
 3 files changed, 70 insertions(+), 3 deletions(-)
 create mode 100644 tests/MongoFramework.Benchmarks/EntityCollectionGetEntryBenchmark.cs

diff --git a/src/MongoFramework/Infrastructure/EntityEntryContainer.cs b/src/MongoFramework/Infrastructure/EntityEntryContainer.cs
index 7002aba1..c2d8f024 100644
--- a/src/MongoFramework/Infrastructure/EntityEntryContainer.cs
+++ b/src/MongoFramework/Infrastructure/EntityEntryContainer.cs
@@ -46,11 +46,15 @@ public EntityEntry GetEntry<TCollectionBase>(TCollectionBase entity)
 				var entityDefinition = EntityMapping.GetOrCreateDefinition(collectionType);
 				var entityId = entityDefinition.GetIdValue(entity);
 				var defaultIdValue = entityDefinition.GetDefaultId();
+				var isDefaultId = Equals(entityId, defaultIdValue);
 				foreach (var entry in entries)
 				{
-					if (Equals(entityId, defaultIdValue) && ReferenceEquals(entry.Entity, entity))
+					if (isDefaultId)
 					{
-						return entry;
+						if (ReferenceEquals(entry.Entity, entity))
+						{
+							return entry;
+						}
 					}
 					else
 					{
diff --git a/src/MongoFramework/Infrastructure/Mapping/EntityDefinition.cs b/src/MongoFramework/Infrastructure/Mapping/EntityDefinition.cs
index da034cff..175aa032 100644
--- a/src/MongoFramework/Infrastructure/Mapping/EntityDefinition.cs
+++ b/src/MongoFramework/Infrastructure/Mapping/EntityDefinition.cs
@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
+using System.Linq.Expressions;
 using System.Reflection;
 
 namespace MongoFramework.Infrastructure.Mapping;
@@ -25,9 +26,31 @@ public sealed record PropertyDefinition
 	public PropertyInfo PropertyInfo { get; init; }
 	public string ElementName { get; init; }
 
+	private Func<object, object> getValueDelegate;
 	public object GetValue(object entity)
 	{
-		return PropertyInfo.GetValue(entity);
+		if (getValueDelegate is null)
+		{
+			// Effectively results in the following expression
+			// object t => (object)(({PropertyType})t).{PropertyName}
+			var parameter = Expression.Parameter(typeof(object), "t");
+			var lambda = Expression.Lambda<Func<object, object>>(
+				Expression.Convert(
+					Expression.MakeMemberAccess(
+						Expression.Convert(
+							parameter,
+							PropertyInfo.DeclaringType
+						),
+						PropertyInfo
+					),
+					typeof(object)
+				), 
+				parameter
+			);
+			getValueDelegate = lambda.Compile();
+		}
+
+		return getValueDelegate(entity);
 	}
 
 	public void SetValue(object entity, object value)
diff --git a/tests/MongoFramework.Benchmarks/EntityCollectionGetEntryBenchmark.cs b/tests/MongoFramework.Benchmarks/EntityCollectionGetEntryBenchmark.cs
new file mode 100644
index 00000000..88fd9cab
--- /dev/null
+++ b/tests/MongoFramework.Benchmarks/EntityCollectionGetEntryBenchmark.cs
@@ -0,0 +1,40 @@
+using BenchmarkDotNet.Attributes;
+using BenchmarkDotNet.Jobs;
+using MongoFramework.Infrastructure;
+
+namespace MongoFramework.Benchmarks;
+
+[SimpleJob(RuntimeMoniker.Net60), MemoryDiagnoser]
+public class EntityEntryContainerBenchmark
+{
+	[Params(100, 1_000, 10_000)]
+	public int EntryCount;
+
+	private EntityEntryContainer Container;
+	private TestEntity[] Entities;
+
+	private class TestEntity
+	{
+		public string Id { get; set; }
+	}
+
+	[GlobalSetup]
+	public void Setup()
+	{
+		Container = new EntityEntryContainer();
+		Entities = new TestEntity[EntryCount];
+		for (var i = 0; i < Entities.Length; i++)
+		{
+			Entities[i] = new TestEntity();
+		}
+	}
+
+	[Benchmark]
+	public void SetEntityState()
+	{
+		for (var i = 0; i < Entities.Length; i++)
+		{
+			Container.SetEntityState(Entities[i], EntityEntryState.Added);
+		}
+	}
+}