fix: normalize Milvus similarity scores for threshold filtering (#4880)

* fix: normalize Milvus similarity scores for threshold filtering

* refactor: refact Milvus similarity score normalization #4879

---------

Co-authored-by: 강나훈 <nahoon.kang@mnc.ai>

Author: ejrtks1020

packages/components/nodes/vectorstores/Milvus/Milvus.ts

@@ -395,7 +395,18 @@ const similaritySearchVectorWithScore = async (query: number[], k: number, vecto
                 }
             }
         })
-        results.push([new Document(fields), result.score])
+        let normalizedScore = result.score
+        switch (vectorStore.indexCreateParams.metric_type) {
+            case MetricType.L2:
+                normalizedScore = 1 / (1 + result.score)
+                break
+            case MetricType.IP:
+            case MetricType.COSINE:
+                normalizedScore = (result.score + 1) / 2
+                break
+        }
+
+        results.push([new Document(fields), normalizedScore])
     })
     return results
 }