Hi, the same is happening to me.
I’m running Docker compose like you, and I notice that Docker is reporting an error when you click on the “Add widget” button.
I suppose the query is not working because of the second error line: server_1 | [2018-07-20 08:37:23,095][PID:15][INFO][werkzeug] 172.19.0.1 - - [20/Jul/2018 08:37:23] “GET /api/queries/recent HTTP/1.1” 500 -
But I don’t know how to solve this issue 
Any help? Thanks!
These are the errors that I am getting from the terminal:
server_1 | [2018-07-20 08:37:23,017][PID:15][INFO][metrics] method=GET path=/api/queries/recent endpoint=recent_queries status=500 content_type=? content_length=-1 duration=94301.05 query_count=3 query_duration=10.66
server_1 | [2018-07-20 08:37:23,095][PID:15][INFO][werkzeug] 172.19.0.1 - - [20/Jul/2018 08:37:23] “GET /api/queries/recent HTTP/1.1” 500 -
server_1 | Traceback (most recent call last):
server_1 | File “/usr/local/lib/python2.7/dist-packages/flask/app.py”, line 2000, in call
server_1 | return self.wsgi_app(environ, start_response)
server_1 | File “/usr/local/lib/python2.7/dist-packages/werkzeug/contrib/fixers.py”, line 152, in call
server_1 | return self.app(environ, start_response)
server_1 | File “/usr/local/lib/python2.7/dist-packages/flask/app.py”, line 1991, in wsgi_app
server_1 | response = self.make_response(self.handle_exception(e))
server_1 | File “/usr/local/lib/python2.7/dist-packages/flask_restful/init.py”, line 271, in error_router
server_1 | return original_handler(e)
server_1 | File “/usr/local/lib/python2.7/dist-packages/flask/app.py”, line 1567, in handle_exception
server_1 | reraise(exc_type, exc_value, tb)
server_1 | File “/usr/local/lib/python2.7/dist-packages/flask_restful/init.py”, line 268, in error_router
server_1 | return self.handle_error(e)
server_1 | File “/usr/local/lib/python2.7/dist-packages/flask/app.py”, line 1988, in wsgi_app
server_1 | response = self.full_dispatch_request()
server_1 | File “/usr/local/lib/python2.7/dist-packages/flask/app.py”, line 1641, in full_dispatch_request
server_1 | rv = self.handle_user_exception(e)
server_1 | File “/usr/local/lib/python2.7/dist-packages/flask_restful/init.py”, line 271, in error_router
server_1 | return original_handler(e)
server_1 | File “/usr/local/lib/python2.7/dist-packages/flask/app.py”, line 1544, in handle_user_exception
server_1 | reraise(exc_type, exc_value, tb)
server_1 | File “/usr/local/lib/python2.7/dist-packages/flask_restful/init.py”, line 268, in error_router
server_1 | return self.handle_error(e)
server_1 | File “/usr/local/lib/python2.7/dist-packages/flask/app.py”, line 1639, in full_dispatch_request
server_1 | rv = self.dispatch_request()
server_1 | File “/usr/local/lib/python2.7/dist-packages/flask/app.py”, line 1625, in dispatch_request
server_1 | return self.view_functionsrule.endpoint
server_1 | File “/usr/local/lib/python2.7/dist-packages/flask_restful/init.py”, line 481, in wrapper
server_1 | return self.make_response(data, code, headers=headers)
server_1 | File “/usr/local/lib/python2.7/dist-packages/flask_restful/init.py”, line 510, in make_response
server_1 | resp = self.representations[mediatype](data, *args, **kwargs)
server_1 | File “/app/redash/handlers/api.py”, line 41, in json_representation
server_1 | resp = make_response(json_dumps(data), code)
server_1 | File “/app/redash/utils/init.py”, line 89, in json_dumps
server_1 | return json.dumps(data, cls=JSONEncoder)
server_1 | File “/usr/lib/python2.7/json/init.py”, line 251, in dumps
server_1 | sort_keys=sort_keys, **kw).encode(obj)
server_1 | File “/usr/lib/python2.7/json/encoder.py”, line 207, in encode
server_1 | chunks = self.iterencode(o, _one_shot=True)
server_1 | File “/usr/lib/python2.7/json/encoder.py”, line 270, in iterencode
server_1 | return _iterencode(o, 0)
server_1 | File “/app/redash/utils/init.py”, line 85, in default
server_1 | super(JSONEncoder, self).default(o)
server_1 | File “/usr/lib/python2.7/json/encoder.py”, line 184, in default
server_1 | raise TypeError(repr(o) + " is not JSON serializable")