Support Apache Kylin in EngineSpec (apache#4925)

* Support Apache Kylin in EngineSpec

* Fix flake8

superset/db_engine_specs.py

@@ -1314,6 +1314,32 @@ class DruidEngineSpec(BaseEngineSpec):
     inner_joins = False
 
 
+class KylinEngineSpec(BaseEngineSpec):
+    """Dialect for Apache Kylin"""
+
+    engine = 'kylin'
+
+    time_grains = (
+        Grain('Time Column', _('Time Column'), '{col}', None),
+        Grain('second', _('second'), 'SECOND({col})', 'PT1S'),
+        Grain('minute', _('minute'), 'MINUTE({col})', 'PT1M'),
+        Grain('hour', _('hour'), 'HOUR({col})', 'PT1H'),
+        Grain('month', _('month'), 'MONTH({col})', 'P1M'),
+        Grain('quarter', _('quarter'), 'QUARTER({col})', 'P0.25Y'),
+        Grain('year', _('year'), 'YEAR({col})', 'P1Y'),
+    )
+
+    @classmethod
+    def convert_dttm(cls, target_type, dttm):
+        tt = target_type.upper()
+        if tt == 'DATE':
+            return "CAST('{}' AS DATE)".format(dttm.isoformat()[:10])
+        if tt == 'TIMESTAMP':
+            return "CAST('{}' AS TIMESTAMP)".format(
+                dttm.strftime('%Y-%m-%d %H:%M:%S'))
+        return "'{}'".format(dttm.strftime('%Y-%m-%d %H:%M:%S'))
+
+
 engines = {
     o.engine: o for o in globals().values()
     if inspect.isclass(o) and issubclass(o, BaseEngineSpec)}