sqlalchemy/alembic · error · TypeError

can't return inspector as this AutogenContext has no databas

Error message

can't return inspector as this AutogenContext has no database connection

What it means

The AutogenContext.inspector property raises this when the migration context has no live database connection. Autogenerate needs to reflect the database schema, which requires an open Connection; in offline ('sql') mode, or when configure() was called against a MigrationContext with no bind, reflection is impossible and the property refuses to return a bogus inspector.

Source

Thrown at alembic/autogenerate/api.py:406

            object_filters.append(include_object)
        if include_name:
            name_filters.append(include_name)

        self._object_filters = object_filters
        self._name_filters = name_filters

        self.migration_context = migration_context
        self.connection = self.migration_context.bind
        self.dialect = self.migration_context.dialect

        self.imports = set()
        self.opts: dict[str, Any] = opts
        self._has_batch: bool = False

    @util.memoized_property
    def inspector(self) -> Inspector:
        if self.connection is None:
            raise TypeError(
                "can't return inspector as this "
                "AutogenContext has no database connection"
            )
        return inspect(self.connection)

    @contextlib.contextmanager
    def _within_batch(self) -> Iterator[None]:
        self._has_batch = True
        yield
        self._has_batch = False

    def run_name_filters(
        self,
        name: str | None,
        type_: NameFilterType,
        parent_names: NameFilterParentNames,
    ) -> bool:
        """Run the context's name filters and return True if the targets

View on GitHub (pinned to 44fb345033)

Solutions

1. Switch env.py to online mode: use engine.connect() (or run_migrations_async with an async engine) and pass the connection to context.configure(connection=conn).
2. If offline SQL generation is genuinely intended, do not invoke autogenerate (which needs reflection); generate an empty revision and hand-write the SQL.
3. Ensure context.configure() receives a non-None connection before any call that reads autogen_context.inspector.

Example fix

// before
context.configure(url=DATABASE_URL)  # offline, no connection
# autogenerate invoked -> TypeError
// after
with engine.connect() as conn:
    context.configure(connection=conn, target_metadata=target_metadata)
    with context.begin_transaction():
        context.run_migrations()

from alembic.runtime.migration import MigrationContext
mc = MigrationContext.get()
if mc is None or getattr(mc, "bind", None) is None:
    raise RuntimeError("Cannot autogenerate without a DB connection; configure env.py in online mode.")

def has_connection(ctx) -> bool:
    return getattr(getattr(ctx, "migration_context", ctx), "bind", None) is not None

When it happens

Trigger: Calling command.autogenerate (alembic revision --autogenerate), or any code path that touches autogen_context.inspector, while the MigrationContext.bind is None. This occurs when env.py is configured for offline (as_sql=True) generation but an autogenerate comparison is still attempted, or when run_migrations is invoked without setting up a connection via online mode.

Common situations: A partially-written env.py that mixes offline and online configuration; running 'alembic revision --autogenerate' against an env.py that was set up for 'alembic upgrade sql' generation; a custom command that constructs MigrationContext.configure() without passing a connection.

Related errors

• Cannot call run_async in SQL mode
• Duplicate table keys across multiple MetaData objects: %s
• Autogenerate rendering of SQL Expression language constructs
• Can only return single object for UpgradeOps traverse
• Can only return single object for DowngradeOps traverse

AI-assisted analysis of sqlalchemy/alembic@44fb345033 (2026-08-04). Data as JSON: /data/errors/105989ba4713c07e.json. Report an issue: GitHub.