text: Title: Bulk update values with SQLAlchemy
  Body: Since aiopg does not support bulk insert (https://github.com/aio-libs/aiopg/issues/112), so I use this to insert everything in a single query:
  ```
  await conn.execute(
      sa_foo_table
      .insert()
      .values([
          dict(name='name1', x=1),
          dict(name='name2', x=2),
          dict(name='name3', x=3),
      ])
  )
  ```
  Is there any such thing for bulk updating? Because if I update one by one, it might take quite some time (there are thousands of rows).