Change Milvus truncate method

Changed truncate method for milvus vector store. Now keeps the collection and only delete the data.

packages/dbgpt-ext/src/dbgpt_ext/storage/vector_store/milvus_store.py

@@ -728,14 +728,29 @@ class MilvusStore(VectorStoreBase):
         return metadata_filter_expr
 
 def truncate(self):
-        """Truncate milvus collection."""
-        logger.info(f"begin truncate milvus collection:{self.collection_name}")
-        from pymilvus import utility
-
+    """检测pymilvus安装"""
+    try:
+        from pymilvus import Collection, utility       
+    except ImportError:
+        raise ValueError(
+            "Could not import pymilvus python package. "
+            "Please install it with `pip install pymilvus`."
+        )
+    """安全清空 Milvus summary collection 中所有数据，但不删除 collection 本身"""
+    logger.info(f"Begin truncate Milvus collection: {self.collection_name}")
+    # 先判断 collection 是否存在
     if utility.has_collection(self.collection_name):
-            utility.drop_collection(self.collection_name)
+        collection = Collection(self.collection_name)
+        # Load collection 必须调用，才能执行 delete
+        collection.load()
+        # 通过pk_id删除所有数据
+        collection.delete("pk_id >= 0")
+        # flush 确保数据删除被提交
+        collection.flush()
+        logger.info(f"Truncate Milvus collection {self.collection_name} success")
+    else:
+        logger.warning(f"Collection {self.collection_name} not found, skip truncate.")
         
-        logger.info(f"truncate milvus collection {self.collection_name} success")
 
     def full_text_search(
         self, text: str, topk: int = 10, filters: Optional[MetadataFilters] = None