diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 20e1dd2..cedceaa 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -49,7 +49,7 @@ jobs:
       OPENAI_BASE_URL: ${{ secrets.OPENAI_BASE_URL }}
       OPENAI_API_KEY: ${{ secrets.OPENAI_API_KEY }}
       DEFAULT_EMBED_MODEL: text-embedding-ada-002
-      DEFAULT_CHAT_MODEL: gpt-3.5-turbo
+      DEFAULT_CHAT_MODEL: gpt-4o-mini
       HF_TOKENIZER_PATH: 01-ai/Yi-6B-Chat
       DEFAULT_CHUNK_SIZE: 300
       DEFAULT_CHUNK_OVERLAP: 100
diff --git a/src/cardinal/vectorstore/auto.py b/src/cardinal/vectorstore/auto.py
index f907bb1..7131553 100644
--- a/src/cardinal/vectorstore/auto.py
+++ b/src/cardinal/vectorstore/auto.py
@@ -29,12 +29,10 @@ def create(cls, name: str, texts: Sequence[str], data: Sequence[T], drop_old: Op
         return _get_vectorstore().create(name, texts, data, drop_old)
 
     def insert(self, texts: Sequence[str], data: Sequence[T]) -> None:
-        self._vectorstore.insert(texts, data)
-        return self._flush()
+        return self._vectorstore.insert(texts, data)
 
     def delete(self, condition: "Condition") -> None:
-        self._vectorstore.delete(condition)
-        return self._flush()
+        return self._vectorstore.delete(condition)
 
     def search(
         self, query: str, top_k: Optional[int] = 4, condition: Optional["Condition"] = None
@@ -47,11 +45,8 @@ def exists(self) -> bool:
     def destroy(self) -> None:
         return self._vectorstore.destroy()
     
-    def _flush(self) -> None:
-        if isinstance(self._vectorstore, Milvus):
-            return self._vectorstore.store.flush()
-        else:
-            return None
+    def flush(self) -> None:
+        return self._vectorstore.flush()
 
 
 _vectorstores: Dict[str, Type["VectorStore"]] = {}
diff --git a/src/cardinal/vectorstore/chroma.py b/src/cardinal/vectorstore/chroma.py
index ee6a914..47690da 100644
--- a/src/cardinal/vectorstore/chroma.py
+++ b/src/cardinal/vectorstore/chroma.py
@@ -145,3 +145,6 @@ def destroy(self) -> None:
         client = _get_chroma_client()
         client.delete_collection(self.name)
         self.store = None
+
+    def flush(self) -> None:
+        return None
diff --git a/src/cardinal/vectorstore/milvus.py b/src/cardinal/vectorstore/milvus.py
index 1f5f8c6..f1a22cb 100644
--- a/src/cardinal/vectorstore/milvus.py
+++ b/src/cardinal/vectorstore/milvus.py
@@ -177,3 +177,7 @@ def destroy(self):
         self._try_init_and_check_exists()
         self.store.drop()
         self.store = None
+
+    def flush(self) -> None:
+        return self.store.flush()
+    
\ No newline at end of file
diff --git a/tests/vectorstore/test_vector_store.py b/tests/vectorstore/test_vector_store.py
index 1960379..d63af0e 100644
--- a/tests/vectorstore/test_vector_store.py
+++ b/tests/vectorstore/test_vector_store.py
@@ -11,12 +11,13 @@ class Animal(BaseModel):
 
 
 def test_vector_store():
-    vectorStore = AutoVectorStore[Animal](name="test")
-    assert(not vectorStore.exists())  # False
-    vectorStore.insert(texts=texts, data=data)
-    vectorStore.delete(AutoCondition(key="name", value="dog", op=Operator.Eq))
-    assert(vectorStore.search(query="dog", top_k=2)[0][0] == data[2])
-    assert(vectorStore.search(query="dog", top_k=2)[1][0] == data[1])
+    vectorstore = AutoVectorStore[Animal](name="test")
+    assert(not vectorstore.exists())  # False
+    vectorstore.insert(texts=texts, data=data)
+    vectorstore.delete(AutoCondition(key="name", value="dog", op=Operator.Eq))
+    vectorstore.flush()
+    assert(vectorstore.search(query="dog", top_k=2)[0][0] == data[2])
+    assert(vectorstore.search(query="dog", top_k=2)[1][0] == data[1])
     # [(Animal(name='puppy'), 0.8510237336158752), (Animal(name='llama'), 1.1970627307891846)]
-    assert(vectorStore.exists())  # True
-    vectorStore.destroy()
+    assert(vectorstore.exists())  # True
+    vectorstore.destroy()