Disable Datasource sql polymorphism & Fix refresh Druid metadata.

dashed/models.py

@@ -840,8 +840,12 @@ def latest_metadata(self):
             return
         max_time = results[0]['result']['maxTime']
         max_time = parse(max_time)
-        intervals = (max_time - timedelta(seconds=1)).isoformat() + '/'
-        intervals += (max_time + timedelta(seconds=1)).isoformat()
+        # Query segmentMetadata for 7 days back. However, due to a bug,
+        # we need to set this interval to more than 1 day ago to exclude realtime segments, which
+        # trigged a bug (fixed in druid 0.8.2).
+        # https://groups.google.com/forum/#!topic/druid-user/gVCqqspHqOQ
+        intervals = (max_time - timedelta(days=7)).isoformat() + '/'
+        intervals += (max_time - timedelta(days=1)).isoformat()
         segment_metadata = client.segment_metadata(
             datasource=self.datasource_name,
             intervals=intervals)
@@ -1114,7 +1118,8 @@ class DruidColumn(Model):
     datasource_name = Column(
         String(250),
         ForeignKey('datasources.datasource_name'))
-    datasource = relationship('DruidDatasource', backref='columns')
+    # Setting enable_typechecks=False disables polymorphic inheritance.
+    datasource = relationship('DruidDatasource', backref='columns', enable_typechecks=False)
     column_name = Column(String(256))
     is_active = Column(Boolean, default=True)
     type = Column(String(32))