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Propagate element metadata to chunks in MEDI chunkers #7516

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5d3bd56
Propagate element metadata to chunks in MEDI chunkers
luisquintanilla May 7, 2026
966e7ec
fix: correct metadata timing in chunkers and add boundary tests
luisquintanilla Jun 8, 2026
8bac32d
test: add SemanticSimilarityChunker metadata propagation tests
luisquintanilla Jun 8, 2026
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56 changes: 53 additions & 3 deletions src/Libraries/Microsoft.Extensions.DataIngestion/Chunkers/DocumentTokenChunker.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -46,6 +46,7 @@ public override async IAsyncEnumerable<IngestionChunk<string>> ProcessAsync(Inge

int stringBuilderTokenCount = 0;
StringBuilder stringBuilder = new();
Dictionary<string, object>? accumulatedMetadata = null;
foreach (IngestionDocumentElement element in document.EnumerateContent())
{
cancellationToken.ThrowIfCancellationRequested();
Expand All @@ -57,6 +58,7 @@ public override async IAsyncEnumerable<IngestionChunk<string>> ProcessAsync(Inge

int contentToProcessTokenCount = _tokenizer.CountTokens(elementContent!, considerNormalization: false);
ReadOnlyMemory<char> contentToProcess = elementContent.AsMemory();
bool elementMetadataAccumulated = false;
while (stringBuilderTokenCount + contentToProcessTokenCount >= _maxTokensPerChunk)
{
int index = _tokenizer.GetIndexByTokenCount(
Expand All @@ -66,35 +68,59 @@ public override async IAsyncEnumerable<IngestionChunk<string>> ProcessAsync(Inge
out int _,
considerNormalization: false);

// Accumulate metadata the first time this element contributes content.
if (!elementMetadataAccumulated && index > 0)
{
AccumulateMetadata(element, ref accumulatedMetadata);
elementMetadataAccumulated = true;
}

unsafe
{
fixed (char* ptr = &MemoryMarshal.GetReference(contentToProcess.Span))
{
_ = stringBuilder.Append(ptr, index);
}
}
yield return FinalizeChunk();
yield return FinalizeChunk(ref accumulatedMetadata);

contentToProcess = contentToProcess.Slice(index);
contentToProcessTokenCount = _tokenizer.CountTokens(contentToProcess.Span, considerNormalization: false);
}

// Accumulate metadata if the element only contributed content after the loop.
if (!elementMetadataAccumulated)
{
AccumulateMetadata(element, ref accumulatedMetadata);
}

_ = stringBuilder.Append(contentToProcess);
stringBuilderTokenCount += contentToProcessTokenCount;
}

if (stringBuilder.Length > 0)
{
yield return FinalizeChunk();
yield return FinalizeChunk(ref accumulatedMetadata);
}
yield break;

IngestionChunk<string> FinalizeChunk()
IngestionChunk<string> FinalizeChunk(ref Dictionary<string, object>? metadata)
{
IngestionChunk<string> chunk = new IngestionChunk<string>(
content: stringBuilder.ToString(),
document: document,
context: string.Empty);

if (metadata is { Count: > 0 })
{
foreach (var kvp in metadata)
{
chunk.Metadata[kvp.Key] = kvp.Value;
}

metadata = null;
}

_ = stringBuilder.Clear();
stringBuilderTokenCount = 0;

Expand All @@ -121,5 +147,29 @@ IngestionChunk<string> FinalizeChunk()
}
}

private static void AccumulateMetadata(IngestionDocumentElement element, ref Dictionary<string, object>? accumulated)
{
if (!element.HasMetadata)
{
return;
}

accumulated ??= [];
foreach (var kvp in element.Metadata)
{
if (kvp.Value is not null)
{
#if NET
accumulated.TryAdd(kvp.Key, kvp.Value);
#else
if (!accumulated.ContainsKey(kvp.Key))
{
accumulated[kvp.Key] = kvp.Value;
}
#endif
}
}
}

}
}
71 changes: 69 additions & 2 deletions src/Libraries/Microsoft.Extensions.DataIngestion/Chunkers/ElementsChunker.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -36,6 +36,7 @@ internal IEnumerable<IngestionChunk<string>> Process(IngestionDocument document,
{
// Not using yield return here as we use ref structs.
List<IngestionChunk<string>> chunks = [];
Dictionary<string, object>? accumulatedMetadata = null;

int contextTokenCount = CountTokens(context.AsSpan());
int totalTokenCount = contextTokenCount;
Expand Down Expand Up @@ -70,12 +71,15 @@ internal IEnumerable<IngestionChunk<string>> Process(IngestionDocument document,
int elementTokenCount = CountTokens(semanticContent.AsSpan());
if (elementTokenCount + totalTokenCount <= _maxTokensPerChunk)
{
// Element fits in the current chunk — accumulate its metadata here.
AccumulateMetadata(element, ref accumulatedMetadata);
totalTokenCount += elementTokenCount;
AppendNewLineAndSpan(_currentChunk, semanticContent.AsSpan());
}
else if (element is IngestionDocumentTable table)
{
ValueStringBuilder tableBuilder = new(initialCapacity: 8000);
bool tableMetadataAccumulated = false;

try
{
Expand Down Expand Up @@ -113,6 +117,13 @@ internal IEnumerable<IngestionChunk<string>> Process(IngestionDocument document,
// We append the table as long as it's not just the header.
if (rowIndex != 1)
{
// Accumulate metadata before first table content append.
if (!tableMetadataAccumulated)
{
AccumulateMetadata(element, ref accumulatedMetadata);
tableMetadataAccumulated = true;
}

AppendNewLineAndSpan(_currentChunk, tableBuilder.AsSpan(0, tableLength - Environment.NewLine.Length));
}

Expand All @@ -137,6 +148,12 @@ internal IEnumerable<IngestionChunk<string>> Process(IngestionDocument document,
totalTokenCount += lastRowTokens;
}

// Accumulate metadata before appending remaining table content.
if (!tableMetadataAccumulated)
{
AccumulateMetadata(element, ref accumulatedMetadata);
}

AppendNewLineAndSpan(_currentChunk, tableBuilder.AsSpan(0, tableLength - Environment.NewLine.Length));
}
finally
Expand All @@ -147,6 +164,7 @@ internal IEnumerable<IngestionChunk<string>> Process(IngestionDocument document,
else
{
ReadOnlySpan<char> remainingContent = semanticContent.AsSpan();
bool elementMetadataAccumulated = false;

while (!remainingContent.IsEmpty)
{
Expand All @@ -170,6 +188,13 @@ internal IEnumerable<IngestionChunk<string>> Process(IngestionDocument document,
tokenCount = CountTokens(remainingContent.Slice(0, index));
}

// Accumulate metadata the first time this element contributes content.
if (!elementMetadataAccumulated)
{
AccumulateMetadata(element, ref accumulatedMetadata);
elementMetadataAccumulated = true;
}

totalTokenCount += tokenCount;
ReadOnlySpan<char> spanToAppend = remainingContent.Slice(0, index);
AppendNewLineAndSpan(_currentChunk, spanToAppend);
Expand All @@ -196,7 +221,9 @@ internal IEnumerable<IngestionChunk<string>> Process(IngestionDocument document,

if (totalTokenCount > contextTokenCount)
{
chunks.Add(new(_currentChunk.ToString(), document, context));
var chunk = new IngestionChunk<string>(_currentChunk.ToString(), document, context);
ApplyMetadata(chunk, accumulatedMetadata);
chunks.Add(chunk);
}

_currentChunk.Clear();
Expand All @@ -205,7 +232,10 @@ internal IEnumerable<IngestionChunk<string>> Process(IngestionDocument document,

void Commit()
{
chunks.Add(new(_currentChunk.ToString(), document, context));
var chunk = new IngestionChunk<string>(_currentChunk.ToString(), document, context);
ApplyMetadata(chunk, accumulatedMetadata);
chunks.Add(chunk);
accumulatedMetadata = null;

// We keep the context in the current chunk as it's the same for all elements.
_currentChunk.Remove(
Expand Down Expand Up @@ -268,6 +298,43 @@ private static void AddMarkdownTableSeparatorRow(int columnCount, ref ValueStrin
vsb.Append(Environment.NewLine);
}

private static void AccumulateMetadata(IngestionDocumentElement element, ref Dictionary<string, object>? accumulated)
{
if (!element.HasMetadata)
{
return;
}

accumulated ??= [];
foreach (var kvp in element.Metadata)
{
if (kvp.Value is not null)
{
#if NET
accumulated.TryAdd(kvp.Key, kvp.Value);
#else
if (!accumulated.ContainsKey(kvp.Key))
{
accumulated[kvp.Key] = kvp.Value;
}
#endif
}
}
}

private static void ApplyMetadata(IngestionChunk<string> chunk, Dictionary<string, object>? accumulated)
{
if (accumulated is null or { Count: 0 })
{
return;
}

foreach (var kvp in accumulated)
{
chunk.Metadata[kvp.Key] = kvp.Value;
}
}

private int CountTokens(ReadOnlySpan<char> input)
=> _tokenizer.CountTokens(input, considerNormalization: false);
}
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