fix: add auto_refresh option for OpenSearch Serverless compatibility (#3893)

Co-authored-by: Zaid Malhis <Malhis@users.noreply.github.com>

mem0/vector_stores/opensearch.py

@@ -39,6 +39,8 @@ class OpenSearchDB(VectorStoreBase):
 
         self.collection_name = config.collection_name
         self.embedding_model_dims = config.embedding_model_dims
+        self.auto_refresh = config.auto_refresh
+
         self.create_col(self.collection_name, self.embedding_model_dims)
 
     def create_index(self) -> None:
@@ -148,8 +150,6 @@ class OpenSearchDB(VectorStoreBase):
             }
             try:
                 self.client.index(index=self.collection_name, body=body)
-                # Force refresh to make documents immediately searchable for tests
-                self.client.indices.refresh(index=self.collection_name)
 
                 results.append(
                     OutputData(
@@ -162,6 +162,14 @@ class OpenSearchDB(VectorStoreBase):
                 logger.error(f"Error inserting vector {id_}: {e}", exc_info=True)
                 raise
 
+        # Refresh once after the full batch (not per document) if explicitly enabled.
+        # Disabled by default for Serverless compatibility: OpenSearch Serverless does not
+        # support the indices.refresh() API, and refreshing per document would cause a
+        # cluster-level I/O stall on every insert.
+        # See: https://docs.aws.amazon.com/opensearch-service/latest/developerguide/serverless-genref.html
+        if self.auto_refresh:
+            self.client.indices.refresh(index=self.collection_name)
+
         return results
 
     def search(