The VectorData adapter

RecursiveAI.OneIndex.VectorData is a vector-store collection over OneIndex for Microsoft.Extensions.VectorData (version 10.11.0 of the abstractions, the one dependency). It covers what the abstraction defines: collections, upsert, get, delete, vector search with filters, and keyword plus vector hybrid search.

var store = new OneIndexVectorStore("data/vectors");          // a directory; new OneIndexVectorStore() keeps collections in memory
var hotels = store.GetCollection<string, Hotel>("hotels");
await hotels.EnsureCollectionExistsAsync();
await hotels.UpsertAsync(hotel);                                // every write is committed before it returns
await foreach (var r in hotels.SearchAsync(queryVector, top: 5, new() { Filter = h => h.Rating >= 4 }))
    Console.WriteLine($"{r.Record.Name} {r.Score}");

What is supported

• Keys string, Guid, int, long. A Guid key is generated when the record carries Guid.Empty and the key is auto-generated (the default for Guid). Asking for a collection with a key type other than the record's key property throws InvalidOperationException.
• Data properties: strings (full-text indexed when IsFullTextIndexed), integers, floating point numbers, bool, DateTime, DateTimeOffset, string collections. IsIndexed makes a property filterable.
• Vector properties ReadOnlyMemory<float> or float[], with the distances cosine similarity and distance, dot product, negative dot product, and Euclidean (squared) distance. Scores come back in the unit of the chosen distance function. The vector index is the engine's: flat below the segment threshold, HNSW above.
• Filters are the abstraction's LINQ predicates; they are applied while the neighbours are chosen, so a filtered search returns a full page when enough records pass. Skip, ScoreThreshold, IncludeVectors work.
• Hybrid search (IKeywordHybridSearchable): the keywords search one full-text property (the one named by AdditionalProperty, or the only one; none or several without a choice throws), fused with the vector by reciprocal rank fusion (hybrid.md).
• Records are described by the abstraction's attributes or by a VectorStoreCollectionDefinition.

What is not

• Dynamic collections (GetDynamicCollection, dictionary records) and embedding generation by the store: NotSupported. Pass vectors yourself.
• Distance functions Manhattan and Hamming.
• Data-type suite. Each of its tests also creates a dynamic collection, so all 16 are excluded; the typed path (Guid, DateOnly, TimeOnly, nullable values, string collections) is covered by ContractTests. Filters comparing a whole array (r.StringArray == array) are not translatable.
• Registration extensions. The package ships no AddOneIndex... dependency-injection extension (it would add a dependency beyond the abstraction); applications register OneIndexVectorStore and their collections as services, as the tests do. Embedding generators are not resolved from the container (EmbeddingGeneratorIsResolved is excluded).
• A caveat on Guid keys: the abstraction's key-type test also exercises a dynamic collection, which is not supported, so that one test is excluded.

Reflection, trimming and AOT

The adapter reads and writes user record types through reflection, as the abstraction itself does. OneIndexVectorStore.GetCollection and OneIndexRecords<TKey, TRecord> carry RequiresUnreferencedCode and RequiresDynamicCode, so a trimmed or NativeAOT application gets warnings at the call, not silent breakage. The package is therefore not marked IsAotCompatible or IsTrimmable. The core package stays reflection-free; an application that needs AOT uses SearchIndex<T> with the generated mapping directly.

Conformance

The tests run the abstraction's own conformance suite (Microsoft.Extensions.VectorData.ConformanceTests 10.11.0) against a store over a temporary directory, plus 8 contract tests of our own.

Filters comparing with null and Contains / Any over a collection property, excluded before, now pass (10 tests). Wired suites: collection management, distance functions, index kinds, filters (typed), basic, no-data, no-vector and multi-vector models, key types, hybrid search, dependency injection, data types (all excluded). Not wired: dynamic-model, embedding-generation and embedding-type suites (no dynamic collections, no generated embeddings). A plain dotnet test runs them all; the unsupported cases skip themselves, each naming the feature.