Fix out of range panic on query

And clarify in Godoc that nResults is the *maximum* number of results.

collection.go

@@ -327,7 +327,8 @@ type Result struct {
 //
 //   - queryText: The text to search for. Its embedding will be created using the
 //     collection's embedding function.
-//   - nResults: The number of results to return. Must be > 0.
+//   - nResults: The maximum number of results to return. Must be > 0.
+//     There can be fewer results if a filter is applied.
 //   - where: Conditional filtering on metadata. Optional.
 //   - whereDocument: Conditional filtering on documents. Optional.
 func (c *Collection) Query(ctx context.Context, queryText string, nResults int, where, whereDocument map[string]string) ([]Result, error) {
@@ -348,7 +349,8 @@ func (c *Collection) Query(ctx context.Context, queryText string, nResults int,
 //   - queryEmbedding: The embedding of the query to search for. It must be created
 //     with the same embedding model as the document embeddings in the collection.
 //     The embedding will be normalized if it's not the case yet.
-//   - nResults: The number of results to return. Must be > 0.
+//   - nResults: The maximum number of results to return. Must be > 0.
+//     There can be fewer results if a filter is applied.
 //   - where: Conditional filtering on metadata. Optional.
 //   - whereDocument: Conditional filtering on documents. Optional.
 func (c *Collection) QueryEmbedding(ctx context.Context, queryEmbedding []float32, nResults int, where, whereDocument map[string]string) ([]Result, error) {
@@ -395,8 +397,16 @@ func (c *Collection) QueryEmbedding(ctx context.Context, queryEmbedding []float3
 		return nil, fmt.Errorf("couldn't get most similar docs: %w", err)
 	}
 
-	res := make([]Result, 0, nResults)
-	for i := 0; i < nResults; i++ {
+	// We return nResults or len(nMaxDocs), whichever is smaller.
+	// The latter can be the case if the collection has fewer documents than nResults
+	// or if the filtering reduced the number of documents.
+	resNum := nResults
+	if len(nMaxDocs) < nResults {
+		resNum = len(nMaxDocs)
+	}
+
+	res := make([]Result, 0, resNum)
+	for i := 0; i < resNum; i++ {
 		res = append(res, Result{
 			ID:         nMaxDocs[i].docID,
 			Metadata:   c.documents[nMaxDocs[i].docID].Metadata,
@@ -406,7 +416,6 @@ func (c *Collection) QueryEmbedding(ctx context.Context, queryEmbedding []float3
 		})
 	}
 
-	// Return the top nResults
 	return res, nil
 }