Add exists check for dpt table

Author: Matti Remes

pandas_gbq/gbq.py

@@ -1010,6 +1010,9 @@ class _Table(GbqConnector):
 
     partition_decorator = '$'
 
+    def _is_date_partitioned_table(self, table_id):
+        return self.partition_decorator in table_id
+
     def __init__(self, project_id, dataset_id, reauth=False, verbose=False,
                  private_key=None):
         self.dataset_id = dataset_id
@@ -1031,8 +1034,12 @@ def exists(self, table_id):
         from google.api_core.exceptions import NotFound
 
         table_ref = self.client.dataset(self.dataset_id).table(table_id)
+
         try:
-            self.client.get_table(table_ref)
+            table = self.client.get_table(table_ref)
+            if self._is_date_partitioned_table(table_id):
+                return table.num_rows > 0
+
             return True
         except NotFound:
             return False