CommunityToolkit.VectorData.Chroma

CommunityToolkit.VectorData.Chroma

Chroma provider for Microsoft.Extensions.VectorData, by the .NET Community Toolkit.

Chroma is an open-source vector database for AI applications.

The provider is built on ChromaDotNet.Client, a .NET client for Chroma and Chroma Cloud.

Quick start

1. Run Chroma with Docker:

docker run -d --name chroma -p 8000:8000 chromadb/chroma

1. Install the NuGet package:

dotnet add package CommunityToolkit.VectorData.Chroma

For more information, see the Microsoft.Extensions.VectorData documentation.

Limitations

• On Chroma Cloud, a vector search returns at most 300 results, Skip included, the default quota of Chroma Cloud: beyond that, Chroma Cloud answers with a quota error.
• Chroma does not store empty lists, so an empty array or list comes back as null.
• Array and list properties, like the namespaces of the TextSearchStore of Semantic Kernel, need Chroma 1.5.0 or later.
• On self-hosted Chroma 1.0.21 to 1.5.9, a vector search can miss a record after an upsert, while a get still finds it. It is KD-49 in the compatibility notes of ChromaDotNet.Client. The environment variable RAYON_NUM_THREADS=1 on the server makes it much rarer. In the client, ChromaUpsertStrategy.SkipUnchangedEmbeddings writes a record whose vector does not change without its vector, so that write does not touch the vector index.
• On Chroma Cloud, a record has at most 32 metadata keys, and a null value counts as one. The provider writes every data property, null or not. A write with null values that would take a record beyond 32 keys throws an ArgumentException. With WithReadsBeyondKeyQuota(), the client reads such a record first and sends only the null values of the keys it has. Two writes of the same record at the same time can then mix.
• On Chroma Cloud, a metadata key has at most 36 bytes in UTF-8. With a data property whose storage name is longer, the collection is created, but every upsert throws a VectorStoreException with the quota error of Chroma Cloud.
• On Chroma Cloud, Contains on the full-text property throws an ArgumentException for a text of fewer than 3 characters. Once Chroma Cloud has indexed the records, such a filter would find no record, and its negation every record.

The connection string does not set WithUpsertStrategy and WithReadsBeyondKeyQuota(). Set them on the options of a ChromaClient created in code, and pass it to the vector store:

var options = new ChromaConfigurationOptions("http://localhost:8000")
    .WithUpsertStrategy(ChromaUpsertStrategy.SkipUnchangedEmbeddings);

builder.Services.AddChromaVectorStore(_ => new ChromaClient(options));