[Add] get_newest_bar_data in database.py

[Add] get_newest_tick_data in database.py

vnpy/trader/database/database.py

@@ -1,7 +1,7 @@
 from abc import ABC, abstractmethod
 from datetime import datetime
 from enum import Enum
-from typing import Sequence, TYPE_CHECKING
+from typing import Sequence, TYPE_CHECKING, Optional
 
 if TYPE_CHECKING:
     from vnpy.trader.constant import Interval, Exchange  # noqa
@@ -51,3 +51,28 @@ class BaseDatabaseManager(ABC):
         datas: Sequence["TickData"],
     ):
         pass
+
+    @abstractmethod
+    def get_newest_bar_data(
+        self,
+        symbol: str,
+        exchange: "Exchange",
+        interval: "Interval"
+    ) -> Optional["BarData"]:
+        """
+        If there is data in database, return the one with greatest datetime(newest one)
+        otherwise, return None
+        """
+        pass
+
+    @abstractmethod
+    def get_newest_tick_data(
+        self,
+        symbol: str,
+        exchange: "Exchange",
+    ) -> Optional["TickData"]:
+        """
+        If there is data in database, return the one with greatest datetime(newest one)
+        otherwise, return None
+        """
+        pass