diff --git a/superset/tasks/slack_util.py b/superset/tasks/slack_util.py
index ef647ebd2a5a2..08dcb16c25442 100644
--- a/superset/tasks/slack_util.py
+++ b/superset/tasks/slack_util.py
@@ -18,15 +18,13 @@
 from io import IOBase
 from typing import cast, Union
 
+from flask import current_app
 from retry.api import retry
 from slack import WebClient
 from slack.errors import SlackApiError
 from slack.web.slack_response import SlackResponse
 
-from superset import app
-
 # Globals
-config = app.config  # type: ignore
 logger = logging.getLogger("tasks.slack_util")
 
 
@@ -34,6 +32,7 @@
 def deliver_slack_msg(
     slack_channel: str, subject: str, body: str, file: Union[str, IOBase]
 ) -> None:
+    config = current_app.config
     client = WebClient(token=config["SLACK_API_TOKEN"], proxy=config["SLACK_PROXY"])
     # files_upload returns SlackResponse as we run it in sync mode.
     response = cast(
diff --git a/superset/viz.py b/superset/viz.py
index 2d9083f982635..08f176bc42035 100644
--- a/superset/viz.py
+++ b/superset/viz.py
@@ -21,6 +21,7 @@
 Superset can render.
 """
 import copy
+import dataclasses
 import inspect
 import logging
 import math
@@ -42,7 +43,6 @@
     Union,
 )
 
-import dataclasses
 import geohash
 import numpy as np
 import pandas as pd
@@ -323,7 +323,8 @@ def query_obj(self) -> QueryObjectDict:
         gb = self.groupby
         metrics = self.all_metrics or []
         columns = form_data.get("columns") or []
-        groupby = list(set(gb + columns))
+        # merge list and dedup while preserving order
+        groupby = list(OrderedDict.fromkeys(gb + columns))
 
         is_timeseries = self.is_timeseries
         if DTTM_ALIAS in groupby: