Unable to change column comment with Alembic

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#46 2025年10月14日に作成コメント 0 件リアクション 1 件担当者 0 名 GitHub で見る

まだ誰も着手していません。

評価

難易度: 3/5
見積もり時間: 1〜2日
初心者へのやさしさ: 48/100

issue の種類: バグ
明瞭さ: おおむね明確
活発さ: 停滞
技術スタック: python, sqlalchemy
領域: databases

調査の方向性

databricks.sqlalchemy._ddl.DatabricksDDLCompiler から開始し、Alembic の ColumnComment がどのように SQLAlchemy のコンパイルに到達するかを追跡します。リンクされた sqlalchemy-redshift の issue と動作を比較し、その後、op.alter_column が報告された UnsupportedCompilationError を発生させずにカラムコメントを追加または変更できることを確認します。

索引モデルが issue の本文から書いたものです。

説明

We're using databricks-sqlalchemy with Alembic, and have found that we are unable to add or change comments on columns. Creating a new column with a comment works fine though.

Let me know if there's any more information I can provide, or if I should open this issue with SQLAlchemy or Alembic.

from alembic import op

op.alter_column(
    'some_table',
    'some_column',
    comment='my column comment',
)

An exception is thrown:

 can't render element of type <class 'alembic.ddl.base.ColumnComment'>: <class 'alembic.ddl.base.ColumnComment'> construct has no default compilation handler.

Click to See full backtrace

Traceback (most recent call last):
  File "<redacted>lib/python3.12/site-packages/sqlalchemy/sql/visitors.py", line 137, in _compiler_dispatch
    meth = getter(visitor)
           ^^^^^^^^^^^^^^^
AttributeError: 'DatabricksDDLCompiler' object has no attribute 'visit_clause'

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "<redacted>lib/python3.12/site-packages/sqlalchemy/ext/compiler.py", line 523, in _wrap_existing_dispatch
    return existing_dispatch(element, compiler, **kw)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "<redacted>lib/python3.12/site-packages/sqlalchemy/sql/visitors.py", line 139, in _compiler_dispatch
    return visitor.visit_unsupported_compilation(self, err, **kw)  # type: ignore  # noqa: E501
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "<redacted>lib/python3.12/site-packages/sqlalchemy/sql/compiler.py", line 902, in visit_unsupported_compilation
    raise exc.UnsupportedCompilationError(self, type(element)) from err
sqlalchemy.exc.UnsupportedCompilationError: Compiler <databricks.sqlalchemy._ddl.DatabricksDDLCompiler object at 0x140c5f980> can't render element of type <class 'alembic.ddl.base.ColumnComment'> (Background on this error at: https://sqlalche.me/e/20/l7de)

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "<redacted>bin/alembic", line 8, in <module>
    sys.exit(main())
             ^^^^^^
  File "<redacted>/lib/python3.12/site-packages/alembic/config.py", line 988, in main
    CommandLine(prog=prog).main(argv=argv)
  File "<redacted>/lib/python3.12/site-packages/alembic/config.py", line 978, in main
    self.run_cmd(cfg, options)
  File "<redacted>/lib/python3.12/site-packages/alembic/config.py", line 912, in run_cmd
    fn(
  File "<redacted>/lib/python3.12/site-packages/alembic/command.py", line 483, in upgrade
    script.run_env()
  File "<redacted>/lib/python3.12/site-packages/alembic/script/base.py", line 551, in run_env
    util.load_python_file(self.dir, "env.py")
  File "<redacted>/lib/python3.12/site-packages/alembic/util/pyfiles.py", line 114, in load_python_file
    module = load_module_py(module_id, path)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "<redacted>/lib/python3.12/site-packages/alembic/util/pyfiles.py", line 134, in load_module_py
    spec.loader.exec_module(module)  # type: ignore
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "<frozen importlib._bootstrap_external>", line 995, in exec_module
  File "<frozen importlib._bootstrap>", line 488, in _call_with_frames_removed
  File "/Users/<redacted>/PycharmProjects/up-ingest-pipeline/databricks/migrations/env.py", line 220, in <module>
    run_migrations_online()
  File "/Users/<redacted>/PycharmProjects/up-ingest-pipeline/databricks/migrations/env.py", line 208, in run_migrations_online
    context.run_migrations(
  File "<string>", line 8, in run_migrations
  File "<redacted>/lib/python3.12/site-packages/alembic/runtime/environment.py", line 946, in run_migrations
    self.get_context().run_migrations(**kw)
  File "<redacted>/lib/python3.12/site-packages/alembic/runtime/migration.py", line 623, in run_migrations
    step.migration_fn(**kw)
  File "<redacted>", line 29, in upgrade
    op.alter_column(
  File "<string>", line 8, in alter_column
  File "<string>", line 3, in alter_column
  File "<redacted>/lib/python3.12/site-packages/alembic/operations/ops.py", line 1973, in alter_column
    return operations.invoke(alt)
           ^^^^^^^^^^^^^^^^^^^^^^
  File "<redacted>/lib/python3.12/site-packages/alembic/operations/base.py", line 441, in invoke
    return fn(self, operation)
           ^^^^^^^^^^^^^^^^^^^
  File "<redacted>/lib/python3.12/site-packages/alembic/operations/toimpl.py", line 53, in alter_column
    operations.impl.alter_column(
  File "<redacted>/lib/python3.12/site-packages/alembic/ddl/impl.py", line 343, in alter_column
    self._exec(
  File "<redacted>/lib/python3.12/site-packages/alembic/ddl/impl.py", line 246, in _exec
    return conn.execute(construct, params)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "<redacted>/lib/python3.12/site-packages/sqlalchemy/engine/base.py", line 1416, in execute
    return meth(
           ^^^^^
  File "<redacted>/lib/python3.12/site-packages/sqlalchemy/sql/ddl.py", line 180, in _execute_on_connection
    return connection._execute_ddl(
           ^^^^^^^^^^^^^^^^^^^^^^^^
  File "<redacted>/lib/python3.12/site-packages/sqlalchemy/engine/base.py", line 1524, in _execute_ddl
    compiled = ddl.compile(
               ^^^^^^^^^^^^
  File "<redacted>/lib/python3.12/site-packages/sqlalchemy/sql/elements.py", line 309, in compile
    return self._compiler(dialect, **kw)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "<redacted>/lib/python3.12/site-packages/sqlalchemy/sql/ddl.py", line 69, in _compiler
    return dialect.ddl_compiler(dialect, self, **kw)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "<redacted>/lib/python3.12/site-packages/sqlalchemy/sql/compiler.py", line 870, in __init__
    self.string = self.process(self.statement, **compile_kwargs)
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "<redacted>/lib/python3.12/site-packages/sqlalchemy/sql/compiler.py", line 915, in process
    return obj._compiler_dispatch(self, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "<redacted>/lib/python3.12/site-packages/sqlalchemy/ext/compiler.py", line 538, in <lambda>
    lambda *arg, **kw: existing(*arg, **kw),
                       ^^^^^^^^^^^^^^^^^^^^
  File "<redacted>/lib/python3.12/site-packages/sqlalchemy/ext/compiler.py", line 591, in __call__
    expr = fn(element, compiler, **kw)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "<redacted>/lib/python3.12/site-packages/sqlalchemy/ext/compiler.py", line 525, in _wrap_existing_dispatch
    raise exc.UnsupportedCompilationError(
sqlalchemy.exc.UnsupportedCompilationError: Compiler <databricks.sqlalchemy._ddl.DatabricksDDLCompiler object at 0x140c5f980> can't render element of type <class 'alembic.ddl.base.ColumnComment'>: <class 'alembic.ddl.base.ColumnComment'> construct has no default compilation handler. (Background on this error at: https://sqlalche.me/e/20/l7de)

NOTE: A very similar issue was opened in sqlalchemy-redshift and I wonder if the solution is similar