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The collection held under a name, created on first request.

public VectorStoreCollection<TKey, TRecord> GetCollection<TKey, TRecord>(string name, VectorStoreCollectionDefinition definition = null) where TKey : notnull where TRecord : class

Parameters — name is the collection's name, and the key the store holds it under. definition is an explicit schema; null reads the key, vector and data attributes on TRecord instead.

Returns — a LodestarVectorStoreCollection, typed as the abstraction's VectorStoreCollection<TKey, TRecord>. Cast it to IKeywordHybridSearchable<TRecord> to reach LodestarVectorStoreCollection.HybridSearchAsync.

Exceptions — ArgumentNullException when name is null. ArgumentException when name is already held over a different TKey or TRecord and has not been deleted since, or when the schema is unusable: no key property, a key property whose type is not TKey, no vector property, a vector property that does not hold ReadOnlyMemory<float>, a full-text indexed property that is not a string, or a definition naming a property TRecord lacks. NotSupportedException when the vector property declares a DistanceFunction other than CosineSimilarity.

Example — the same name twice is the same collection, and asking for it does not create it.

using Lodestar.Extensions.VectorData;
using Microsoft.Extensions.VectorData;

static async Task<string> AskTwiceAsync()
{
    using var store = new LodestarVectorStore();
    VectorStoreCollection<string, Note> first = store.GetCollection<string, Note>("notes");
    VectorStoreCollection<string, Note> second = store.GetCollection<string, Note>("notes");

    bool before = await store.CollectionExistsAsync("notes");
    await first.EnsureCollectionExistsAsync();
    bool after = await store.CollectionExistsAsync("notes");

    return $"{ReferenceEquals(first, second)} {before} {after}";
}

string seen = AskTwiceAsync().GetAwaiter().GetResult();  // => True False True

Remarks — the first request decides the schema. A second call with the same name returns the collection already held, and its definition is not read: a store cannot hold two schemas under one name, and quietly rebuilding the first would drop its records. A different TKey or TRecord is refused rather than ignored, because the cast that would follow could only fail somewhere less helpful. A deleted name is free again: once LodestarVectorStore.EnsureCollectionDeletedAsync has run and nothing has written to the collection since, a different TKey or TRecord gets a new collection under that name, while the same ones still get the instance already held.

The collection is created, not made to exist. It answers false to LodestarVectorStore.CollectionExistsAsync until LodestarVectorStoreCollection.EnsureCollectionExistsAsync or a write, which is the abstraction's contract for a server-backed store and holds here too.

Every collection takes the LodestarVectorStoreOptions the store was constructed with; a collection wanting different ones is constructed directly.

Applies to — net10.0, netstandard2.0.

See also — LodestarVectorStore, LodestarVectorStoreCollection.