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STJ avoid full document string allocation #5908

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201969f
Avoid full-document string allocation in CosmosSystemTextJsonSerializer
May 28, 2026
205f87c
Add changelog entry for CosmosSystemTextJsonSerializer allocation fix
May 28, 2026
a8fb219
Expand changelog entry to cover CPU, transcoding, and bandwidth wins
May 28, 2026
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7 changes: 4 additions & 3 deletions Microsoft.Azure.Cosmos/src/Serializer/CosmosSystemTextJsonSerializer.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -62,7 +62,9 @@ public override T FromStream<T>(Stream stream)

if (CosmosObject.TryCreateFromBuffer(content, out CosmosObject cosmosObject))
{
return System.Text.Json.JsonSerializer.Deserialize<T>(cosmosObject.ToString(), this.jsonSerializerOptions);
IJsonWriter jsonWriter = JsonWriter.Create(JsonSerializationFormat.Text);
cosmosObject.WriteTo(jsonWriter);
return System.Text.Json.JsonSerializer.Deserialize<T>(jsonWriter.GetResult().Span, this.jsonSerializerOptions);
}
else
{
Expand Down Expand Up @@ -133,8 +135,7 @@ public override string SerializeMemberName(MemberInfo memberInfo)
private T DeserializeStream<T>(
Stream stream)
{
using StreamReader reader = new (stream);
return System.Text.Json.JsonSerializer.Deserialize<T>(reader.ReadToEnd(), this.jsonSerializerOptions);
return System.Text.Json.JsonSerializer.Deserialize<T>(stream, this.jsonSerializerOptions);
}
}
}
2 changes: 2 additions & 0 deletions changelog.md
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Expand Up @@ -30,6 +30,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0

#### Other Changes

- Performance: Avoid full-document UTF-16 `string` allocation and redundant UTF-8↔UTF-16 transcoding in `CosmosSystemTextJsonSerializer` read paths (binary and text). UTF-8 bytes are now fed directly into `Utf8JsonReader` via `JsonSerializer.Deserialize<T>(Stream, ...)` and `Deserialize<T>(ReadOnlySpan<byte>, ...)`, reducing CPU, memory bandwidth, and GC pressure (including LOH pressure for larger documents).

### <a name="3.61.0-preview.0"/> [3.61.0-preview.0](https://www.nuget.org/packages/Microsoft.Azure.Cosmos/3.61.0-preview.0) - 2026-5-18

#### Features Added
Expand Down