+ removed some useless Exists check

+ identifier now contains data
+ adddeferred

src/Default.cs

@@ -5,22 +5,32 @@ public static class Defaults
 	/// <summary>
 	/// Wildcard is used to specify "any component/tag".<br/>It's mostly used for queries.
 	/// </summary>
-	public struct Wildcard { public static EcsID ID = Lookup.Component<Wildcard>.Value.ID; }
+	public readonly struct Wildcard { public static readonly EcsID ID = Lookup.Component<Wildcard>.Value.ID; }
 
 	/// <summary>
 	/// Built-in tag.<br/>Shortcut for child.Add{ChildOf}(parent);
 	/// </summary>
 	public struct ChildOf { }
 
 	/// <summary>
-	/// Built-in tag.<br/>Used in combination with <see cref="Name"/>
+	/// Built-in component.<br/>Used in combination with <see cref="Name"/>
 	/// </summary>
-	public struct Identifier { }
+	public readonly struct Identifier
+	{
+		public static readonly EcsID ID = Lookup.Component<Identifier>.Value.ID;
+
+		public Identifier(string name) => Data = name;
+
+		public readonly string Data;
+	}
 
 	/// <summary>
 	/// Built-in tag.<br/>Used in combination with <see cref="Identifier"/>
 	/// </summary>
-	public readonly struct Name { internal Name(string value) => Value = value; public readonly string Value; }
+	public readonly struct Name
+	{
+		public static readonly EcsID ID = Lookup.Component<Name>.Value.ID;
+	}
 
     /// <summary>
     /// Built-in tag.<br/>Used to make a component/tag unique when adding a Pair.<para/>

src/World.Deferred.cs

@@ -38,7 +38,7 @@ public void EndDeferred()
 	}
 
 
-	private void SetDeferred<T>(EcsID entity) where T : struct
+	private void AddDeferred<T>(EcsID entity) where T : struct
 	{
 		ref readonly var cmp = ref Component<T>();
 

src/World.Public.cs

@@ -57,7 +57,7 @@ public World(ulong maxComponentId = 256)
 		setCommon(Entity<Unset>(), nameof(Unset));
 
 		static EntityView setCommon(EntityView entity, string name)
-			=> entity.Add<DoNotDelete>().Set<Identifier, Name>(new (name));
+			=> entity.Add<DoNotDelete>().Set<Identifier>(new (name), Defaults.Name.ID);
 
 		OnPluginInitialization?.Invoke(this);
     }
@@ -88,12 +88,12 @@ public void Dispose()
         _archRoot.Clear();
         _typeIndex.Clear();
 		_cachedComponents.Clear();
+		_names.Clear();
 
 		foreach (var query in _cachedQueries.Values)
 			query.Dispose();
 
 		_cachedQueries.Clear();
-		_namesToEntity.Clear();
         Archetypes.Clear();
     }
 
@@ -185,25 +185,22 @@ public EntityView Entity<T>() where T : struct
 	{
 		ref readonly var cmp = ref Component<T>();
 
-		var entity = Entity(cmp.ID);
-		if (entity.ID.IsPair())
-			return entity;
+		var entId = cmp.ID;
 
-		var name = Lookup.Component<T>.Name;
-
-		if (_namesToEntity.TryGetValue(name, out var id))
-		{
-			if (entity.ID != id)
-				EcsAssert.Panic(false, $"You must declare the component before the entity '{id}' named '{name}'");
-		}
-		else
+		if (!entId.IsPair())
 		{
-			_namesToEntity[name] = entity;
-			entity.Set<Identifier, Name>(new (name));
-			GetRecord(entity).Flags |= EntityFlags.IsUnique;
+			ref var record = ref GetRecord(entId);
+
+			if ((record.Flags & EntityFlags.HasName) == 0)
+			{
+				record.Flags |= EntityFlags.HasName;
+				var name = Lookup.Component<T>.Name;
+				_names[name] = entId;
+				Set<Identifier>(entId, new (name), Defaults.Name.ID);
+			}
 		}
 
-		return entity;
+		return new EntityView(this, entId);
 	}
 
 	/// <summary>
@@ -214,20 +211,20 @@ public EntityView Entity<T>() where T : struct
 	/// <returns></returns>
 	public EntityView Entity(string name)
 	{
-		if (string.IsNullOrEmpty(name))
+		if (string.IsNullOrWhiteSpace(name))
 			return EntityView.Invalid;
 
 		EntityView entity;
-		if (_namesToEntity.TryGetValue(name, out var id))
+		if (_names.TryGetValue(name, out var id) && (GetRecord(id).Flags & EntityFlags.HasName) != 0)
 		{
 			entity = Entity(id);
 		}
 		else
 		{
 			entity = Entity();
-			_namesToEntity[name] = entity;
-			entity.Set<Identifier, Name>(new (name));
-			GetRecord(entity).Flags |= EntityFlags.IsUnique;
+			GetRecord(entity).Flags |= EntityFlags.HasName;
+			_names[name] = entity;
+			entity.Set<Identifier>(new (name), Defaults.Name.ID);
 		}
 
 		return entity;
@@ -258,12 +255,12 @@ public void Delete(EcsID entity)
 
 			if (record.Flags != EntityFlags.None)
 			{
-				if ((record.Flags & EntityFlags.IsUnique) != 0)
+				if ((record.Flags & EntityFlags.HasName) != 0)
 				{
 					if (Has<Identifier, Name>(entity))
 					{
-						var name = Get<Identifier, Name>(entity).Value;
-						_namesToEntity.Remove(name, out var _);
+						var name = Get<Identifier>(entity, Defaults.Name.ID).Data;
+						_names.Remove(name, out var _);
 					}
 				}
 
@@ -371,7 +368,7 @@ public void Add<T>(EcsID entity) where T : struct
 
 		if (IsDeferred && !Has(entity, cmp.ID))
 		{
-			SetDeferred<T>(entity);
+			AddDeferred<T>(entity);
 
 			return;
 		}
@@ -451,7 +448,7 @@ public void Unset(EcsID entity, EcsID id)
 	/// <param name="entity"></param>
 	/// <returns></returns>
     public bool Has<T>(EcsID entity) where T : struct
-		=> Exists(entity) && Has(entity, Component<T>().ID);
+		=> Has(entity, Component<T>().ID);
 
 	/// <summary>
 	/// Check if the entity has a component or tag.<br/>
@@ -488,6 +485,19 @@ public ref T Get<T>(EcsID entity) where T : struct
 		return ref GetUntrusted<T>(entity, cmp.ID, cmp.Size);
     }
 
+	/// <summary>
+	/// Get the name associated to the entity.
+	/// </summary>
+	/// <param name="id"></param>
+	/// <returns></returns>
+	public string Name(EcsID id)
+	{
+		ref var record = ref GetRecord(id);
+		if ((record.Flags & EntityFlags.HasName) != 0)
+			return Get<Identifier>(id, Defaults.Name.ID).Data;
+		return string.Empty;
+	}
+
 	/// <summary>
 	/// Print the archetype graph.
 	/// </summary>

src/World.Relationship.cs

@@ -27,24 +27,21 @@ private ref readonly ComponentInfo Hack<TAction, TTarget>()
 
 	private void CheckUnique(EcsID entity, EcsID action)
 	{
-		if (Exists(action))
+		// only one (A, *)
+		if (Entity(action).Has<Unique>())
 		{
-			// only one (A, *)
-			if (Entity(action).Has<Unique>())
+			var targetId = Target(entity, action);
+			if (targetId != 0)
 			{
-				var targetId = Target(entity, action);
-				if (targetId != 0)
-				{
-					Unset(entity, action, targetId);
-				}
+				Unset(entity, action, targetId);
 			}
 		}
 	}
 
 	private void CheckSymmetric(EcsID entity, EcsID action, EcsID target)
 	{
 		// (R, B) to A will also add (R, A) to B.
-		if (Exists(action) && Entity(action).Has<Symmetric>() && !Has(target, action, entity))
+		if (Entity(action).Has<Symmetric>() && !Has(target, action, entity))
 		{
 			var pairId = IDOp.Pair(action, entity);
 
@@ -120,12 +117,12 @@ public void Add<TAction>(EcsID entity, EcsID target)
 
 		if (IsDeferred && !Has(entity, act.ID, target))
 		{
-			SetDeferred(entity, pairId);
+			SetDeferred(entity, pairId, null, 0, false);
 
 			return;
 		}
 
-		_ = AttachComponent(entity, pairId, act.Size, act.IsManaged);
+		_ = AttachComponent(entity, pairId, 0, false);
 	}
 
 	/// <summary>
@@ -149,7 +146,7 @@ public void Set<TAction>(EcsID entity, TAction action, EcsID target)
 
 		if (IsDeferred && !Has(entity, act.ID, target))
 		{
-			SetDeferred(entity, pairId);
+			SetDeferred(entity, pairId, action, act.Size, act.IsManaged);
 
 			return;
 		}
@@ -251,7 +248,7 @@ public bool Has<TAction>(EcsID entity, EcsID target)
 	public bool Has(EcsID entity, EcsID action, EcsID target)
 	{
 		var pairId = IDOp.Pair(action, target);
-		return Exists(entity) && Has(entity, pairId);
+		return Has(entity, pairId);
 	}
 
 	/// <summary>
@@ -265,8 +262,10 @@ public void Unset<TAction, TTarget>(EcsID entity)
 		where TAction : struct
 		where TTarget : struct
 	{
-		ref readonly var linkedCmp = ref Hack<TAction, TTarget>();
-		Unset<Relation<TAction, TTarget>>(entity);
+		var first = Component<TAction>().ID;
+		var second = Component<TTarget>().ID;
+		var pairId = IDOp.Pair(first, second);
+		Unset(entity, pairId);
 	}
 
 	/// <summary>
@@ -557,12 +556,7 @@ public static class NameEx
 	/// <returns></returns>
 	public static string Name(this EntityView entity)
 	{
-		if (entity.Has<Identifier, Name>())
-		{
-			return entity.Get<Identifier, Name>().Value;
-		}
-
-		return entity.ID.ToString();
+		return entity.World.Name(entity.ID);
 	}
 }
 

src/World.cs

@@ -9,15 +9,14 @@ public sealed partial class World : IDisposable
 	internal delegate Query QueryFactoryDel(World world, ReadOnlySpan<IQueryTerm> terms);
 
     private readonly Archetype _archRoot;
-    private readonly EntitySparseSet<EcsRecord> _entities = new();
-    private readonly FastIdLookup<Archetype> _typeIndex = new();
+    private readonly EntitySparseSet<EcsRecord> _entities = new ();
+    private readonly FastIdLookup<Archetype> _typeIndex = new ();
     private readonly ComponentComparer _comparer;
 	private readonly EcsID _maxCmpId;
 	private readonly Dictionary<EcsID, Query> _cachedQueries = new ();
-	private readonly object _newEntLock = new object();
-	private readonly ConcurrentDictionary<string, EcsID> _namesToEntity = new ();
 	private readonly FastIdLookup<EcsID> _cachedComponents = new ();
-	private readonly ComponentInfo[] _cache = new ComponentInfo[1024];
+	private readonly Dictionary<string, EcsID> _names = new ();
+	private readonly object _newEntLock = new ();
 
 	private static readonly Comparison<ComponentInfo> _comparisonCmps = (a, b)
 		=> ComponentComparer.CompareTerms(null!, a.ID, b.ID);
@@ -111,10 +110,21 @@ private void DetachComponent(EcsID entity, EcsID id)
 		if (id.IsPair())
 		{
 			(var first, var second) = id.Pair();
+			if ((record.Flags & EntityFlags.HasName) != 0)
+			{
+				if (first == Defaults.Identifier.ID && second == Defaults.Name.ID)
+				{
+
+
+					record.Flags &= ~EntityFlags.HasName;
+				}
+			}
+
 			GetRecord(GetAlive(first)).Flags &= ~EntityFlags.IsAction;
 			GetRecord(GetAlive(second)).Flags &= ~EntityFlags.IsTarget;
 		}
 
+
 		OnComponentUnset?.Invoke(record.EntityView(), new ComponentInfo(id, -1, false));
 
 		BeginDeferred();
@@ -273,5 +283,7 @@ enum EntityFlags
 	None = 1 << 0,
 	IsAction = 1 << 1,
 	IsTarget = 1 << 2,
-	IsUnique = 1 << 3
+	IsUnique = 1 << 3,
+	IsSymmetric = 1 << 4,
+	HasName = 1 << 5
 }

tests/Entity.cs

@@ -323,6 +323,23 @@ public void Declare_NamedEntity_Before_Tag()
 			Assert.Equal(ctx.World.Entity<NormalTag>(), a);
 		}
 
+		[Fact]
+		public void Entity_Name()
+		{
+			using var ctx = new Context();
+
+			var a = ctx.World.Entity("a");
+			Assert.Equal("a", a.Name());
+
+			a.Unset<Defaults.Identifier, Defaults.Name>();
+			Assert.Equal("", a.Name());
+
+			var aa = ctx.World.Entity("a");
+			Assert.True(a.ID != aa.ID);
+
+			Assert.Equal("a", aa.Name());
+		}
+
 		[Fact]
 		public void Entity_Has_Wildcard()
 		{