Fixed data sources being re-indexed after a confidence level change

app/Tests/Tools/EmbeddingSignatureTests.cs

@@ -0,0 +1,72 @@
+using AIStudio.Provider;
+using AIStudio.Settings;
+using AIStudio.Settings.DataModel;
+using AIStudio.Tools.Services;
+
+namespace AIStudio.Tests.Tools;
+
+/// <summary>
+/// Checks what makes the stored embeddings of a data source invalid.
+/// </summary>
+/// <remarks>
+/// The embedding signature decides whether an index survives: when it differs from the one persisted
+/// for a data source, everything stored is thrown away and embedded again. That is the right answer
+/// for anything a vector depends on, and an expensive mistake for everything else. The confidence
+/// level a data source asks of a provider used to be part of it, so changing that one setting
+/// re-embedded every file of the source — at a cloud embedding provider, for real money and no gain.
+/// </remarks>
+[TestFixture]
+public sealed class EmbeddingSignatureTests
+{
+    [Test]
+    public void ChangingTheConfidenceLevelKeepsTheStoredEmbeddings()
+    {
+        var low = DataSource(ConfidenceLevel.LOW);
+        var high = DataSource(ConfidenceLevel.HIGH);
+
+        Assert.That(Signature(high), Is.EqualTo(Signature(low)), "The confidence level changes no vector, so the stored index stays valid and nothing is embedded again.");
+    }
+
+    [Test]
+    public void ChangingTheChunkSizeDropsTheStoredEmbeddings()
+    {
+        var small = DataSource(ConfidenceLevel.LOW) with { MaxChunkTokenLength = 512 };
+        var large = DataSource(ConfidenceLevel.LOW) with { MaxChunkTokenLength = 1024 };
+
+        Assert.That(Signature(large), Is.Not.EqualTo(Signature(small)), "Other chunk boundaries mean other vectors, so the index has to be built again.");
+    }
+
+    [Test]
+    public void ChangingTheEmbeddingModelDropsTheStoredEmbeddings()
+    {
+        var dataSource = DataSource(ConfidenceLevel.LOW);
+
+        Assert.That(
+            Signature(dataSource, EmbeddingProviderFor("text-embedding-3-large")),
+            Is.Not.EqualTo(Signature(dataSource, EmbeddingProviderFor("text-embedding-3-small"))),
+            "Another model means another vector space, so nothing stored may be kept.");
+    }
+
+    private static string Signature(DataSourceLocalDirectory dataSource, EmbeddingProvider? embeddingProvider = null) =>
+        DataSourceEmbeddingService.BuildEmbeddingSignature(
+            dataSource,
+            embeddingProvider ?? EmbeddingProviderFor("text-embedding-3-small"),
+            new(512, 100));
+
+    private static DataSourceLocalDirectory DataSource(ConfidenceLevel confidenceLevel) => new()
+    {
+        Num = 1,
+        Id = "6f1d6a4e-6a5e-4c62-9a4f-0f2d2c8b7a11",
+        Name = "Test data",
+        Description = "Documents used by the tests.",
+        Type = DataSourceType.LOCAL_DIRECTORY,
+        EmbeddingId = "b0a4c4d2-1f3e-4f0a-8c9d-5a6b7c8d9e01",
+        MaxChunkTokenLength = 512,
+        ChunkOverlapTokenLength = 100,
+        ConfidenceLevel = confidenceLevel,
+        Path = "/tmp/test-data",
+    };
+
+    private static EmbeddingProvider EmbeddingProviderFor(string modelId) =>
+        new(1, "b0a4c4d2-1f3e-4f0a-8c9d-5a6b7c8d9e01", "Test embeddings", LLMProviders.OPEN_AI, new(modelId, modelId));
+}