fix(core): Update Milvus truncate method for GraphRAG (#2847)

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

@@ -728,14 +728,30 @@ 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)
-
-        logger.info(f"truncate milvus collection {self.collection_name} success")
+            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."
+            )
 
     def full_text_search(
         self, text: str, topk: int = 10, filters: Optional[MetadataFilters] = None