Refactor get_best_pair to persistence

freqtrade/persistence.py

@@ -421,6 +421,15 @@ class Trade(_DECL_BASE):
             for pair, rate, count in pair_rates
         ]
 
+    @staticmethod
+    def get_best_pair():
+        best_pair = Trade.session.query(
+            Trade.pair, func.sum(Trade.close_profit).label('profit_sum')
+        ).filter(Trade.is_open.is_(False)) \
+            .group_by(Trade.pair) \
+            .order_by(desc('profit_sum')).first()
+        return best_pair
+
     @staticmethod
     def get_open_trades() -> List[Any]:
         """

freqtrade/rpc/rpc.py

@@ -225,11 +225,7 @@ class RPC:
             )
             profit_all_perc.append(profit_percent)
 
-        best_pair = Trade.session.query(
-            Trade.pair, sql.func.sum(Trade.close_profit).label('profit_sum')
-        ).filter(Trade.is_open.is_(False)) \
-            .group_by(Trade.pair) \
-            .order_by(sql.text('profit_sum DESC')).first()
+        best_pair = Trade.get_best_pair()
 
         if not best_pair:
             raise RPCException('no closed trade')

tests/test_persistence.py

@@ -859,3 +859,16 @@ def test_get_overall_performance(fee):
     assert 'pair' in res[0]
     assert 'profit' in res[0]
     assert 'count' in res[0]
+
+
+@pytest.mark.usefixtures("init_persistence")
+def test_get_best_pair(fee):
+
+    res = Trade.get_best_pair()
+    assert res is None
+
+    create_mock_trades(fee)
+    res = Trade.get_best_pair()
+    assert len(res) == 2
+    assert res[0] == 'ETC/BTC'
+    assert res[1] == 0.005