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[Fusion] Write forwarded variables once per fetch #10524

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Merged
tobias-tengler merged 6 commits into from
Oct 13, 2026
Merged

[Fusion] Write forwarded variables once per fetch #10524

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6f16c66
[Fusion] Write forwarded variables once per fetch
tobias-tengler Oct 9, 2026
1294822
[Fusion] Splice forwarded variables into multi-entity fetches
tobias-tengler Oct 9, 2026
458cc4b
Cleanup
tobias-tengler Oct 9, 2026
9e2d6c9
[Fusion] Create the forwarded variable buffer on first use
tobias-tengler Oct 9, 2026
2a992c6
Add extra test
tobias-tengler Oct 9, 2026
5cb5ecf
Merge branch 'main' into tte/fusion-write-forwarded-variables-once
tobias-tengler Oct 13, 2026
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7 changes: 7 additions & 0 deletions src/HotChocolate/Fusion/src/Fusion.Execution/Execution/Results/FetchResultStore.Pooling.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -124,6 +124,13 @@ internal void Clean(int maxCollectTargetRetainLength, int maxDictionaryRetainCap
// reset variable writer (returns excess chunks, keeps the first)
_variableWriter.Clean();

// release the forwarded variable buffer if a large input made it grow
if (_forwardedVariableWriter is { Capacity: > MaxRetainedForwardedVariableCapacity })
{
_forwardedVariableWriter.Dispose();
_forwardedVariableWriter = null;
}

// clear collect target arrays to unroot CompositeResultDocument references;
// if they grew too large during a burst, swap them for smaller ones.
TrimOrClearBuffer(ref _collectTargetA, maxCollectTargetRetainLength);
Expand Down
67 changes: 52 additions & 15 deletions src/HotChocolate/Fusion/src/Fusion.Execution/Execution/Results/FetchResultStore.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,7 @@ namespace HotChocolate.Fusion.Execution.Results;
internal sealed partial class FetchResultStore : IDisposable
{
private const int MaxRetainedDataElementStagingLength = 1024;
private const int MaxRetainedForwardedVariableCapacity = 16 * 1024;
private const int MaxStackAllocPathSegments = 32;

private static readonly ArrayPool<VariableValues> s_variableValuePool = ArrayPool<VariableValues>.Shared;
Expand All @@ -46,6 +47,7 @@ internal sealed partial class FetchResultStore : IDisposable
#endif
private readonly List<IDisposable> _memory = [];
private readonly ChunkedArrayWriter _variableWriter = new();
private PooledArrayWriter? _forwardedVariableWriter;
private readonly JsonWriter _jsonWriter;
private readonly VariableDedupTable _variableDedupTable;
private FusionSchemaDefinition _schema = default!;
Expand Down Expand Up @@ -1038,6 +1040,7 @@ private ImmutableArray<VariableValues> BuildVariableValueSetsFromSnapshot(
VariableValues[]? variableValueSets = null;
var additionalPaths = new AdditionalPathAccumulator();
var nextIndex = 0;
var forwardedVariables = SerializeForwardedVariables(requestVariables, importedEntries.Length);

foreach (var importedEntry in importedEntries)
{
Expand All @@ -1049,13 +1052,7 @@ private ImmutableArray<VariableValues> BuildVariableValueSetsFromSnapshot(
_jsonWriter.Reset(_variableWriter);
var startPosition = _variableWriter.Position;
_jsonWriter.WriteStartObject();

for (var i = 0; i < requestVariables.Count; i++)
{
var field = requestVariables[i];
_jsonWriter.WritePropertyName(field.Name.Value);
WriteValueNode(field.Value);
}
WriteForwardedVariables(requestVariables, forwardedVariables);

if (!TryWriteRequestedRequirementValues(importedEntry.Values, requiredData))
{
Expand Down Expand Up @@ -1133,6 +1130,7 @@ private ImmutableArray<VariableValues> BuildVariableValueSets(
VariableValues[]? variableValueSets = null;
var additionalPaths = new AdditionalPathAccumulator();
var nextIndex = 0;
var forwardedVariables = SerializeForwardedVariables(requestVariables, elements.Length);

foreach (var result in elements)
{
Expand All @@ -1141,14 +1139,7 @@ private ImmutableArray<VariableValues> BuildVariableValueSets(
_jsonWriter.Reset(_variableWriter);
var startPosition = _variableWriter.Position;
_jsonWriter.WriteStartObject();

// Write forwarded variables.
for (var i = 0; i < requestVariables.Count; i++)
{
var field = requestVariables[i];
_jsonWriter.WritePropertyName(field.Name.Value);
WriteValueNode(field.Value);
}
WriteForwardedVariables(requestVariables, forwardedVariables);

// Write requirement fields.
var failed = false;
Expand Down Expand Up @@ -1783,6 +1774,51 @@ private void WriteRawJsonValue(ReadOnlySequence<byte> value)
_jsonWriter.WriteRawValue(value.ToArray());
}

private ReadOnlySpan<byte> SerializeForwardedVariables(
IReadOnlyList<ObjectFieldNode> requestVariables,
int entityCount)
{
if (entityCount < 2 || requestVariables.Count == 0)
{
return [];
}

var writer = _forwardedVariableWriter ??= new PooledArrayWriter();
writer.Reset();
_jsonWriter.Reset(writer);
_jsonWriter.WriteStartObject();

for (var i = 0; i < requestVariables.Count; i++)
{
var field = requestVariables[i];
_jsonWriter.WritePropertyName(field.Name.Value);
WriteValueNode(field.Value);
}

_jsonWriter.WriteEndObject();
_jsonWriter.Reset(_variableWriter);

return writer.WrittenSpan[1..^1];
}

private void WriteForwardedVariables(
IReadOnlyList<ObjectFieldNode> requestVariables,
ReadOnlySpan<byte> serialized)
{
if (!serialized.IsEmpty)
{
_jsonWriter.WriteRawProperties(serialized);
return;
}

for (var i = 0; i < requestVariables.Count; i++)
{
var field = requestVariables[i];
_jsonWriter.WritePropertyName(field.Name.Value);
WriteValueNode(field.Value);
}
}

private void WriteValueNode(IValueNode value)
{
switch (value)
Expand Down Expand Up @@ -2498,6 +2534,7 @@ public void Dispose()

_variableDedupTable.Dispose();
_variableWriter.Dispose();
_forwardedVariableWriter?.Dispose();
_pathPool?.Dispose();
}

Expand Down
219 changes: 219 additions & 0 deletions ...otChocolate/Fusion/test/Fusion.Execution.Tests/Execution/Results/FetchResultStoreTests.cs
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Expand Up @@ -1542,6 +1542,225 @@ input FooKeyInput {
"""));
}

[Fact]
public void CreateVariableValueSets_Should_WriteForwardedVariablesForEveryEntity_When_RequestHasForwardedVariables()
{
// arrange
var schema = ComposeSchema(
"""
# name: test
type Query {
foos: [Foo]
}

type Foo {
id: ID!
}
""");

using var resultArena = new MemoryArena();
using var sourceArena = new MemoryArena();
using var store = CreateLiveStore(
schema,
"{ foos { id } }",
"""{"data":{"foos":[{"id":"1"},{"id":"2"},{"id":"3"}]}}""",
resultArena,
sourceArena);

// act
var result = store.CreateVariableValueSets(
SelectionPath.Root.AppendField("foos"),
[
Field("first", new IntValueNode(10)),
Field("filter", new ObjectValueNode(Field("name", new StringValueNode("a\"b"))))
],
[Requirement(schema, "__fusion_1_id", "id", new NamedTypeNode("ID"))]);

// assert
result.Select(entry => Normalize(entry.Values)).MatchInlineSnapshots(
[
"""
{"first":10,"filter":{"name":"a\u0022b"},"__fusion_1_id":"1"}
""",
"""
{"first":10,"filter":{"name":"a\u0022b"},"__fusion_1_id":"2"}
""",
"""
{"first":10,"filter":{"name":"a\u0022b"},"__fusion_1_id":"3"}
"""
]);
}

[Fact]
public void CreateVariableValueSets_Should_WriteForwardedVariables_When_RequestHasSingleEntity()
{
// arrange
var schema = ComposeSchema(
"""
# name: test
type Query {
foos: [Foo]
}

type Foo {
id: ID!
}
""");

using var resultArena = new MemoryArena();
using var sourceArena = new MemoryArena();
using var store = CreateLiveStore(
schema,
"{ foos { id } }",
"""{"data":{"foos":[{"id":"1"}]}}""",
resultArena,
sourceArena);

// act
var result = store.CreateVariableValueSets(
SelectionPath.Root.AppendField("foos"),
[
Field("first", new IntValueNode(10)),
Field("filter", new ObjectValueNode(Field("name", new StringValueNode("a\"b"))))
],
[Requirement(schema, "__fusion_1_id", "id", new NamedTypeNode("ID"))]);

// assert
var entry = Assert.Single(result);
Normalize(entry.Values).MatchInlineSnapshot(
"""
{"first":10,"filter":{"name":"a\u0022b"},"__fusion_1_id":"1"}
""");
}

[Fact]
public void CreateVariableValueSets_Should_WriteForwardedVariablesForRemainingEntities_When_FirstEntityFailsRequirement()
{
// arrange
var schema = ComposeSchema(
"""
# name: test
type Query {
foos: [Foo]
}

type Foo {
id: ID
}
""");

using var resultArena = new MemoryArena();
using var sourceArena = new MemoryArena();
using var store = CreateLiveStore(
schema,
"{ foos { id } }",
"""{"data":{"foos":[{"id":null},{"id":"2"},{"id":"3"}]}}""",
resultArena,
sourceArena);

// act
var result = store.CreateVariableValueSets(
SelectionPath.Root.AppendField("foos"),
[Field("first", new IntValueNode(10))],
[Requirement(schema, "__fusion_1_id", "id", new NonNullTypeNode(new NamedTypeNode("ID")))]);

// assert
result.Select(entry => Normalize(entry.Values)).MatchInlineSnapshots(
[
"""
{"first":10,"__fusion_1_id":"2"}
""",
"""
{"first":10,"__fusion_1_id":"3"}
"""
]);
}

[Fact]
public void CreateVariableValueSetsFromSnapshot_Should_WriteForwardedVariablesForEveryEntry_When_MultipleEntriesAreImported()
{
// arrange
using var source = new FetchResultStore();
using var target = new FetchResultStore();

var first = CreateVariableValues(source, Path(1), Field("__fusion_1_id", new StringValueNode("1")));
var second = CreateVariableValues(source, Path(2), Field("__fusion_1_id", new StringValueNode("2")));
var third = CreateVariableValues(source, Path(3), Field("__fusion_1_id", new StringValueNode("3")));

// act
var result = target.CreateVariableValueSetsFromSnapshot(
[first, second, third],
ImportedKeys("__fusion_1_id"),
[
Field("first", new IntValueNode(10)),
Field("filter", new ObjectValueNode(Field("name", new StringValueNode("a\"b"))))
],
[Requirement("__fusion_1_id")]);

// assert
result.Select(entry => Normalize(entry.Values)).MatchInlineSnapshots(
[
"""
{"first":10,"filter":{"name":"a\u0022b"},"__fusion_1_id":"1"}
""",
"""
{"first":10,"filter":{"name":"a\u0022b"},"__fusion_1_id":"2"}
""",
"""
{"first":10,"filter":{"name":"a\u0022b"},"__fusion_1_id":"3"}
"""
]);
}

[Fact]
public void CreateVariableValueSetsFromSnapshot_Should_WriteForwardedVariables_When_StoreIsReusedAfterLargeInputWasCleaned()
{
// arrange
using var source = new FetchResultStore();
using var target = new FetchResultStore();

var first = CreateVariableValues(source, Path(1), Field("__fusion_1_id", new StringValueNode("1")));
var second = CreateVariableValues(source, Path(2), Field("__fusion_1_id", new StringValueNode("2")));

// a forwarded value above the retained capacity grows the forwarded variable buffer, so Clean releases it
var payload = new string('a', 40_000);

var largeValues = target.CreateVariableValueSetsFromSnapshot(
[first, second],
ImportedKeys("__fusion_1_id"),
[Field("payload", new StringValueNode(payload))],
[Requirement("__fusion_1_id")])
.Select(entry => Normalize(entry.Values))
.ToArray();

target.Clean(maxCollectTargetRetainLength: 256, maxDictionaryRetainCapacity: 256);

// act
var result = target.CreateVariableValueSetsFromSnapshot(
[first, second],
ImportedKeys("__fusion_1_id"),
[Field("first", new IntValueNode(10))],
[Requirement("__fusion_1_id")]);

// assert
string[] expectedLargeValues =
[
$$"""{"payload":"{{payload}}","__fusion_1_id":"1"}""",
$$"""{"payload":"{{payload}}","__fusion_1_id":"2"}"""
];
Assert.Equal(expectedLargeValues, largeValues);

result.Select(entry => Normalize(entry.Values)).MatchInlineSnapshots(
[
"""
{"first":10,"__fusion_1_id":"1"}
""",
"""
{"first":10,"__fusion_1_id":"2"}
"""
]);
}

[Fact]
public void CreateVariableValueSets_Should_ResolveInvariantNames_When_SelectionSetOrdinalsDiffer()
{
Expand Down
1 change: 1 addition & 0 deletions src/HotChocolate/Json/src/Json/HotChocolate.Text.Json.csproj
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Expand Up @@ -16,6 +16,7 @@
<InternalsVisibleTo Include="HotChocolate.Fusion.Execution" />
<InternalsVisibleTo Include="HotChocolate.Types" />
<InternalsVisibleTo Include="HotChocolate.Subscriptions" />
<InternalsVisibleTo Include="HotChocolate.Text.Json.Tests" />
</ItemGroup>

<ItemGroup Condition="'$(TargetFramework)' == 'netstandard2.0'">
Expand Down
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