- test fixup

- get batch mode to fail gracefully, dropping the temp table if
the operation fails
- finish tutorial

1 files changed, 25 insertions, 17 deletions

diff --git a/alembic/batch.py b/alembic/batch.py
index 8470404..7bfcf22 100644
--- a/alembic/batch.py
+++ b/alembic/batch.py
@@ -2,11 +2,15 @@ from sqlalchemy import Table, MetaData, Index, select, Column, \
     ForeignKeyConstraint, cast
 from sqlalchemy import types as sqltypes
 from sqlalchemy.util import OrderedDict
+from . import util
 
 
 class BatchOperationsImpl(object):
     def __init__(self, operations, table_name, schema, recreate,
                  copy_from, table_args, table_kwargs):
+        if not util.sqla_08:
+            raise NotImplementedError(
+                "batch mode requires SQLAlchemy 0.8 or greater.")
         self.operations = operations
         self.table_name = table_name
         self.schema = schema
@@ -174,24 +178,28 @@ class ApplyBatchImpl(object):
         op_impl.prep_table_for_batch(self.table)
         op_impl.create_table(self.new_table)
 
-        op_impl._exec(
-            self.new_table.insert(inline=True).from_select(
-                list(k for k, transfer in
-                     self.column_transfers.items() if 'expr' in transfer),
-                select([
-                    transfer['expr']
-                    for transfer in self.column_transfers.values()
-                    if 'expr' in transfer
-                ])
+        try:
+            op_impl._exec(
+                self.new_table.insert(inline=True).from_select(
+                    list(k for k, transfer in
+                         self.column_transfers.items() if 'expr' in transfer),
+                    select([
+                        transfer['expr']
+                        for transfer in self.column_transfers.values()
+                        if 'expr' in transfer
+                    ])
+                )
+            )
+            op_impl.drop_table(self.table)
+        except:
+            op_impl.drop_table(self.new_table)
+            raise
+        else:
+            op_impl.rename_table(
+                "_alembic_batch_temp",
+                self.table.name,
+                schema=self.table.schema
             )
-        )
-
-        op_impl.drop_table(self.table)
-        op_impl.rename_table(
-            "_alembic_batch_temp",
-            self.table.name,
-            schema=self.table.schema
-        )
 
     def alter_column(self, table_name, column_name,
                      nullable=None,