YACHT-1256: Extracting logic validating source table and backup empti…

…ness.

Adding test: Should make backup if source table is empty and existing backup is also empty (eg. schema change but without adding any data).

src/backup/default_backup_predicate.py

@@ -11,19 +11,20 @@ def test(self, big_query_table_metadata, table_entity):
         if not self._is_possible_to_copy_table(big_query_table_metadata):
             return False
 
-        if self.__table_has_up_to_date_backup(big_query_table_metadata, table_entity):
-            logging.info('Backup is up to date')
-            return False
-
-        return True
-
-    def __table_has_up_to_date_backup(self, big_query_table_metadata, table_entity):
         last_backup = self.__get_last_table_backup_if_any(table_entity)
+
         if not last_backup:
+            return True
+
+        if big_query_table_metadata.is_empty() and last_backup.numBytes > 0:
+            logging.info("Source table is empty. Not empty backup exists.")
             return False
 
-        return self.__is_table_backup_up_to_date(big_query_table_metadata,
-                                                 last_backup)
+        if self.__is_table_backup_up_to_date(big_query_table_metadata, last_backup):
+            logging.info('Backup is up to date')
+            return False
+
+        return True
 
     def __get_last_table_backup_if_any(self, table_entity):
         if table_entity is None:
@@ -45,9 +46,6 @@ def __is_table_backup_up_to_date(self, big_query_table_metadata, last_backup):
         )
         if source_table_last_modified_time > last_backup.last_modified:
             logging.info("Backup time is older than table metadata")
-            if big_query_table_metadata.is_empty() and last_backup.numBytes > 0:
-                logging.info("Source table is empty. Not empty backup exists.")
-                return True
             return False
         return True
 

tests/backup/test_default_backup_predicate.py

@@ -55,7 +55,7 @@ def test_should_return_false_if_schema_is_not_defined(self, _):
     @patch.object(BigQueryTableMetadata, 'is_empty', return_value=True)
     @patch.object(BigQueryTableMetadata, 'get_last_modified_datetime',
                   return_value=datetime(2016, 11, 13, 15, 00))
-    def test_should_return_true_if_table_is_empty(self, _, _1):
+    def test_should_return_true_if_table_is_empty_and_there_is_no_backup(self, _, _1):
         # given
         predicate = DefaultBackupPredicate()
         # when
@@ -171,4 +171,25 @@ def test_should_return_false_if_changed_table_is_empty_and_last_backup_is_not_em
         # then
         self.assertFalse(result, "ShouldBackupPredicate should return FALSE "
                                  "if table was changed after last backup was made,"
-                                 "but source table is empty and bbq has not empty last backup")
+                                 "but source table is empty and bbq has not empty last backup")
+
+    @patch.object(BigQueryTableMetadata, 'is_empty', return_value=True)
+    @patch.object(BigQueryTableMetadata, 'get_last_modified_datetime',
+                  return_value=datetime(2018, 11, 13, 17, 00))
+    def test_should_return_true_if_changed_table_is_empty_and_last_backup_is_also_empty(self, _1, _2):  # nopep8 pylint: disable=C0301
+        # given
+        backup = Backup(
+            parent=self.table.key,
+            last_modified=datetime(2016, 11, 13, 15, 00),
+            numBytes=0
+        )
+        backup.put()
+        predicate = DefaultBackupPredicate()
+
+        # when
+        result = predicate.test(self.big_query_table_metadata, self.table)
+
+        # then
+        self.assertTrue(result, "ShouldBackupPredicate should return True "
+                                 "if table was changed after last backup was made,"
+                                 "but source table is empty and bbq has also empty last backup")