drop_column provided by alembic does not works...

[charlesw1234]

To drop a column:

from pathlib import Path
from typing import Annotated
from sqlalchemy import create_engine, Integer, String
from sqlalchemy.orm import DeclarativeBase, Mapped, mapped_column
from alembic.migration import MigrationContext
from alembic.operations import Operations

intpk = Annotated[int, mapped_column(Integer(), primary_key = True, autoincrement = True)]
class BaseModel(DeclarativeBase): pass

class Building(BaseModel):
    __tablename__ = 'draft_building'
    id: Mapped[intpk]
    name: Mapped[str] = mapped_column(String(64))

engine = create_engine('sqlite:///%s' % (Path('sa2x6.sqlite3').absolute(),))
def create_all():
    Building.metadata.create_all(engine)

def drop_column():
    conn = engine.connect()
    ctx = MigrationContext.configure(conn)
    oper = Operations(ctx)
    column = Building.__table__.columns[1]
    oper.drop_column(Building.__table__.name, column)

The following error encountered:

$ ./python3.sh 
Python 3.11.4 (main, Jun 13 2023, 23:21:17) [GCC 11.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import sa2x6
>>> sa2x6.create_all()
>>> sa2x6.drop_column()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/tester/draft/sqlalchemy/sa2x6.py", line 25, in drop_column
    oper.drop_column(Building.__table__.name, column)
  File "<string>", line 3, in drop_column
  File "/opt/py3/lib/python3.11/site-packages/alembic/operations/ops.py", line 2186, in drop_column
    return operations.invoke(op)
           ^^^^^^^^^^^^^^^^^^^^^
  File "/opt/py3/lib/python3.11/site-packages/alembic/operations/base.py", line 401, in invoke
    return fn(self, operation)
           ^^^^^^^^^^^^^^^^^^^
  File "/opt/py3/lib/python3.11/site-packages/alembic/operations/toimpl.py", line 88, in drop_column
    column = operation.to_column(operations.migration_context)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/py3/lib/python3.11/site-packages/alembic/operations/ops.py", line 2137, in to_column
    return schema_obj.column(self.column_name, NULLTYPE)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/py3/lib/python3.11/site-packages/alembic/operations/schemaobj.py", line 239, in column
    return sa_schema.Column(name, type_, **kw)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/py3/lib/python3.11/site-packages/sqlalchemy/sql/schema.py", line 2151, in __init__
    self._init_items(*cast(_typing_Sequence[SchemaItem], l_args))
  File "/opt/py3/lib/python3.11/site-packages/sqlalchemy/sql/schema.py", line 230, in _init_items
    spwd(self, **kw)
  File "/opt/py3/lib/python3.11/site-packages/sqlalchemy/sql/base.py", line 1328, in _set_parent_with_dispatch
    self._set_parent(parent, **kw)
TypeError: Column._set_parent() missing 2 required keyword-only arguments: 'all_names' and 'allow_replacements'
>>> 

And this code is work with SQLAlchemy1.4 & Alembic, how can I fix it? thanks greatly.

[zzzeek]

alembic drop_column, like all the column level mods, takes column names, not objects. alembic ops don't require existing metadata

    oper.drop_column(Building.__table__.name, "myname")

[CaselIT]

moved to alembic discussions

[charlesw1234]

works for me now, thanks very much.

by the way, ALTER TABLE draft_building DROP COLUMN name; does not work in SQLite3.31.1 which is the default version of ubuntu20.04, but works find for 3.37.2 which is the default version of ubuntu22.04.