[Fusion] Reduce Path Allocations

src/HotChocolate/Fusion/src/Fusion.Execution/Execution/Clients/SourceSchemaHttpClient.cs

@@ -386,19 +386,19 @@ private static int ResolveVariableIndex(
     private static bool TryGetResultPath(
         SourceSchemaClientRequest request,
         int variableIndex,
-        out Path path,
-        out ImmutableArray<Path> additionalPaths)
+        out CompactPath path,
+        out ImmutableArray<CompactPath> additionalPaths)
     {
         if (request.Variables.Length == 0)
         {
-            path = Path.Root;
+            path = CompactPath.Root;
             additionalPaths = [];
             return true;
         }
 
         if ((uint)variableIndex >= (uint)request.Variables.Length)
         {
-            path = Path.Root;
+            path = CompactPath.Root;
             additionalPaths = [];
             return false;
         }
@@ -489,8 +489,8 @@ private void WriteResultToChannel(
         OperationPlanContext context,
         ExecutionNode node,
         NodeResponse nodeResponse,
-        Path path,
-        ImmutableArray<Path> additionalPaths,
+        CompactPath path,
+        ImmutableArray<CompactPath> additionalPaths,
         SourceResultDocument document)
     {
         var sourceSchemaResult = additionalPaths.IsDefaultOrEmpty
@@ -561,7 +561,7 @@ public override async IAsyncEnumerable<SourceSchemaResult> ReadAsResultStreamAsy
             {
                 await foreach (var result in response.ReadAsResultStreamAsync().WithCancellation(cancellationToken))
                 {
-                    var sourceSchemaResult = new SourceSchemaResult(Path.Root, result);
+                    var sourceSchemaResult = new SourceSchemaResult(CompactPath.Root, result);
 
                     configuration.OnSourceSchemaResult?.Invoke(context, node, sourceSchemaResult);
 
@@ -575,7 +575,7 @@ public override async IAsyncEnumerable<SourceSchemaResult> ReadAsResultStreamAsy
                     case 0:
                     {
                         var result = await response.ReadAsResultAsync(cancellationToken);
-                        var sourceSchemaResult = new SourceSchemaResult(Path.Root, result);
+                        var sourceSchemaResult = new SourceSchemaResult(CompactPath.Root, result);
 
                         configuration.OnSourceSchemaResult?.Invoke(context, node, sourceSchemaResult);
 

src/HotChocolate/Fusion/src/Fusion.Execution/Execution/Clients/SourceSchemaResult.cs

@@ -26,22 +26,21 @@ public sealed class SourceSchemaResult : IDisposable
     /// <param name="final">Whether this is the final message in a streaming response.</param>
     /// <param name="additionalPaths">Any additional paths where this result should also be merged.</param>
     public SourceSchemaResult(
-        Path path,
+        CompactPath path,
         SourceResultDocument document,
         FinalMessage final = FinalMessage.Undefined,
-        ImmutableArray<Path> additionalPaths = default)
+        ImmutableArray<CompactPath> additionalPaths = default)
         : this(path, document, final, ownsDocument: true, additionalPaths)
     {
     }
 
     private SourceSchemaResult(
-        Path path,
+        CompactPath path,
         SourceResultDocument document,
         FinalMessage final,
         bool ownsDocument,
-        ImmutableArray<Path> additionalPaths)
+        ImmutableArray<CompactPath> additionalPaths)
     {
-        ArgumentNullException.ThrowIfNull(path);
         ArgumentNullException.ThrowIfNull(document);
 
         _document = document;
@@ -54,13 +53,13 @@ private SourceSchemaResult(
     /// <summary>
     /// The primary path in the composite result into which this source schema result will be merged.
     /// </summary>
-    public Path Path { get; }
+    public CompactPath Path { get; }
 
     /// <summary>
     /// Additional paths where this result should also be merged, used when a single source
     /// schema response satisfies multiple selection sets at different locations.
     /// </summary>
-    public ImmutableArray<Path> AdditionalPaths { get; }
+    public ImmutableArray<CompactPath> AdditionalPaths { get; }
 
     /// <summary>
     /// The <c>data</c> element of the source schema response, or an empty element if the
@@ -132,7 +131,7 @@ public SourceResultElement Extensions
     /// of the underlying document. Used internally when the same result needs to be referenced
     /// at a different location in the composite result.
     /// </summary>
-    internal SourceSchemaResult WithPath(Path path)
+    internal SourceSchemaResult WithPath(CompactPath path)
         => new(path, _document, Final, ownsDocument: false, additionalPaths: []);
 
     /// <summary>

src/HotChocolate/Fusion/src/Fusion.Execution/Execution/FusionOptions.cs

@@ -80,6 +80,27 @@ public int OperationDocumentCacheSize
         }
     } = 256;
 
+    /// <summary>
+    /// Gets or sets the initial capacity of the local path segment pool used during result composition.
+    /// <c>64</c> by default. <c>1</c> is the minimum.
+    /// </summary>
+    public int PathSegmentLocalPoolCapacity
+    {
+        get;
+        set
+        {
+            ExpectMutableOptions();
+
+            if (value < 1)
+            {
+                throw new ArgumentException(
+                    "The path segment local pool capacity must be at least 1.");
+            }
+
+            field = value;
+        }
+    } = 64;
+
     /// <summary>
     /// Gets or sets the default error handling mode.
     /// <see cref="ErrorHandlingMode.Propagate"/> by default.
@@ -160,6 +181,7 @@ public FusionOptions Clone()
             OperationExecutionPlanCacheSize = OperationExecutionPlanCacheSize,
             OperationExecutionPlanCacheDiagnostics = OperationExecutionPlanCacheDiagnostics,
             OperationDocumentCacheSize = OperationDocumentCacheSize,
+            PathSegmentLocalPoolCapacity = PathSegmentLocalPoolCapacity,
             DefaultErrorHandlingMode = DefaultErrorHandlingMode,
             LazyInitialization = LazyInitialization,
             NodeIdSerializerFormat = NodeIdSerializerFormat,

src/HotChocolate/Fusion/src/Fusion.Execution/Execution/Nodes/OperationBatchExecutionNode.cs

@@ -3,6 +3,7 @@
 using System.Runtime.InteropServices;
 using HotChocolate.Execution;
 using HotChocolate.Fusion.Execution.Clients;
+using HotChocolate.Fusion.Text.Json;
 
 namespace HotChocolate.Fusion.Execution.Nodes;
 
@@ -294,7 +295,7 @@ private static void AddErrors(
                 pathBufferLength += 1 + variables[i].AdditionalPaths.Length;
             }
 
-            var pathBuffer = ArrayPool<Path>.Shared.Rent(pathBufferLength);
+            var pathBuffer = ArrayPool<CompactPath>.Shared.Rent(pathBufferLength);
 
             try
             {
@@ -315,7 +316,7 @@ private static void AddErrors(
             finally
             {
                 pathBuffer.AsSpan(0, pathBufferLength).Clear();
-                ArrayPool<Path>.Shared.Return(pathBuffer);
+                ArrayPool<CompactPath>.Shared.Return(pathBuffer);
             }
         }
     }

src/HotChocolate/Fusion/src/Fusion.Execution/Execution/Nodes/OperationExecutionNode.cs

@@ -6,6 +6,7 @@
 using HotChocolate.Execution;
 using HotChocolate.Fusion.Diagnostics;
 using HotChocolate.Fusion.Execution.Clients;
+using HotChocolate.Fusion.Text.Json;
 
 namespace HotChocolate.Fusion.Execution.Nodes;
 
@@ -343,7 +344,7 @@ private static void AddErrors(
                 pathBufferLength += 1 + variables[i].AdditionalPaths.Length;
             }
 
-            var pathBuffer = ArrayPool<Path>.Shared.Rent(pathBufferLength);
+            var pathBuffer = ArrayPool<CompactPath>.Shared.Rent(pathBufferLength);
 
             try
             {
@@ -364,7 +365,7 @@ private static void AddErrors(
             finally
             {
                 pathBuffer.AsSpan(0, pathBufferLength).Clear();
-                ArrayPool<Path>.Shared.Return(pathBuffer);
+                ArrayPool<CompactPath>.Shared.Return(pathBuffer);
             }
         }
     }

src/HotChocolate/Fusion/src/Fusion.Execution/Execution/Nodes/Serialization/JsonOperationPlanFormatter.cs

@@ -58,7 +58,7 @@ public void Format(IBufferWriter<byte> writer, OperationPlan plan, OperationPlan
         }
 
         jsonWriter.WritePropertyName("nodes");
-        WriteNodes(jsonWriter, plan.AllNodes, trace);
+        WriteNodes(jsonWriter, plan.AllNodes, trace, plan.Operation);
 
         jsonWriter.WriteEndObject();
     }
@@ -72,7 +72,7 @@ internal void Format(IBufferWriter<byte> writer, Operation operation, ImmutableA
         WriteOperation(jsonWriter, operation);
 
         jsonWriter.WritePropertyName("nodes");
-        WriteNodes(jsonWriter, allNodes, null);
+        WriteNodes(jsonWriter, allNodes, null, operation);
 
         jsonWriter.WriteEndObject();
     }
@@ -101,7 +101,8 @@ private static void WriteOperation(
     private static void WriteNodes(
         Utf8JsonWriter jsonWriter,
         ImmutableArray<ExecutionNode> allNodes,
-        OperationPlanTrace? trace)
+        OperationPlanTrace? trace,
+        Operation operation)
     {
         jsonWriter.WriteStartArray();
 
@@ -113,19 +114,19 @@ private static void WriteNodes(
             switch (node)
             {
                 case OperationExecutionNode operationNode:
-                    WriteOperationNode(jsonWriter, operationNode, nodeTrace);
+                    WriteOperationNode(jsonWriter, operationNode, nodeTrace, operation);
                     break;
 
                 case OperationBatchExecutionNode batchNode:
-                    WriteOperationBatchNode(jsonWriter, batchNode, nodeTrace);
+                    WriteOperationBatchNode(jsonWriter, batchNode, nodeTrace, operation);
                     break;
 
                 case IntrospectionExecutionNode introspectionNode:
-                    WriteIntrospectionNode(jsonWriter, introspectionNode, nodeTrace);
+                    WriteIntrospectionNode(jsonWriter, introspectionNode, nodeTrace, operation);
                     break;
 
                 case NodeFieldExecutionNode nodeExecutionNode:
-                    WriteNodeFieldNode(jsonWriter, nodeExecutionNode, nodeTrace);
+                    WriteNodeFieldNode(jsonWriter, nodeExecutionNode, nodeTrace, operation);
                     break;
             }
         }
@@ -136,7 +137,8 @@ private static void WriteNodes(
     private static void WriteOperationNode(
         Utf8JsonWriter jsonWriter,
         OperationExecutionNode node,
-        ExecutionNodeTrace? trace)
+        ExecutionNodeTrace? trace,
+        Operation operation)
     {
         jsonWriter.WriteStartObject();
         jsonWriter.WriteNumber("id", node.Id);
@@ -229,15 +231,16 @@ private static void WriteOperationNode(
             jsonWriter.WriteEndArray();
         }
 
-        TryWriteNodeTrace(jsonWriter, trace);
+        TryWriteNodeTrace(jsonWriter, trace, operation);
 
         jsonWriter.WriteEndObject();
     }
 
     private static void WriteOperationBatchNode(
         Utf8JsonWriter jsonWriter,
         OperationBatchExecutionNode node,
-        ExecutionNodeTrace? trace)
+        ExecutionNodeTrace? trace,
+        Operation operation)
     {
         jsonWriter.WriteStartObject();
         jsonWriter.WriteNumber("id", node.Id);
@@ -334,15 +337,16 @@ private static void WriteOperationBatchNode(
             jsonWriter.WriteEndArray();
         }
 
-        TryWriteNodeTrace(jsonWriter, trace);
+        TryWriteNodeTrace(jsonWriter, trace, operation);
 
         jsonWriter.WriteEndObject();
     }
 
     private static void WriteIntrospectionNode(
         Utf8JsonWriter jsonWriter,
         IntrospectionExecutionNode node,
-        ExecutionNodeTrace? trace)
+        ExecutionNodeTrace? trace,
+        Operation operation)
     {
         jsonWriter.WriteStartObject();
         jsonWriter.WriteNumber("id", node.Id);
@@ -363,12 +367,16 @@ private static void WriteIntrospectionNode(
 
         TryWriteConditions(jsonWriter, node);
 
-        TryWriteNodeTrace(jsonWriter, trace);
+        TryWriteNodeTrace(jsonWriter, trace, operation);
 
         jsonWriter.WriteEndObject();
     }
 
-    private static void WriteNodeFieldNode(Utf8JsonWriter jsonWriter, NodeFieldExecutionNode node, ExecutionNodeTrace? trace)
+    private static void WriteNodeFieldNode(
+        Utf8JsonWriter jsonWriter,
+        NodeFieldExecutionNode node,
+        ExecutionNodeTrace? trace,
+        Operation operation)
     {
         jsonWriter.WriteStartObject();
         jsonWriter.WriteNumber("id", node.Id);
@@ -390,12 +398,12 @@ private static void WriteNodeFieldNode(Utf8JsonWriter jsonWriter, NodeFieldExecu
 
         TryWriteConditions(jsonWriter, node);
 
-        TryWriteNodeTrace(jsonWriter, trace);
+        TryWriteNodeTrace(jsonWriter, trace, operation);
 
         jsonWriter.WriteEndObject();
     }
 
-    private static void TryWriteNodeTrace(Utf8JsonWriter jsonWriter, ExecutionNodeTrace? trace)
+    private static void TryWriteNodeTrace(Utf8JsonWriter jsonWriter, ExecutionNodeTrace? trace, Operation operation)
     {
         if (trace is not null)
         {
@@ -413,7 +421,7 @@ private static void TryWriteNodeTrace(Utf8JsonWriter jsonWriter, ExecutionNodeTr
 
                 foreach (var variableSet in trace.VariableSets)
                 {
-                    jsonWriter.WritePropertyName(variableSet.Path.ToString());
+                    jsonWriter.WritePropertyName(variableSet.Path.ToPath(operation).Print());
                     WriteObjectValueNode(jsonWriter, variableSet.Values);
                 }