Catch an arithmetic error

Author: jcjones

partitionmanager/bootstrap.py

@@ -86,7 +86,7 @@ def _plan_partitions_for_time_offsets(
     for (i, offset), is_final in partitionmanager.tools.iter_show_end(
         enumerate(time_offsets)
     ):
-        increase = [x * offset / RATE_UNIT for x in rate_of_change]
+        increase = [x * (offset / RATE_UNIT) for x in rate_of_change]
         predicted_positions = [
             int(p + i) for p, i in zip(ordered_current_pos, increase)
         ]

partitionmanager/bootstrap_test.py

@@ -9,11 +9,19 @@
     _suffix,
     _trigger_column_copies,
     _override_config_to_map_data,
+    _plan_partitions_for_time_offsets,
     calculate_sql_alters_from_state_info,
     write_state_info,
 )
 from .cli import Config
-from .types import DatabaseCommand, Table, SqlInput
+from .types import (
+    DatabaseCommand,
+    Table,
+    SqlInput,
+    MaxValuePartition,
+    ChangePlannedPartition,
+    NewPlannedPartition,
+)
 
 
 class MockDatabase(DatabaseCommand):
@@ -251,3 +259,14 @@ def test_generate_sql_copy_commands(self):
                 "\t\tWHERE `id` = NEW.`id`;",
             ],
         )
+
+    def test_plan_partitions_for_time_offsets(self):
+        parts = _plan_partitions_for_time_offsets(
+            datetime(2021, 3, 3),
+            [timedelta(days=60), timedelta(days=360)],
+            [11943234],
+            [16753227640],
+            MaxValuePartition("p_assumed", count=1),
+        )
+        self.assertIsInstance(parts[0], ChangePlannedPartition)
+        self.assertIsInstance(parts[1], NewPlannedPartition)