1.20.1

1.20.1

Released: October 21, 2026

bug

• [bug] [autogenerate] Fixed issue where a table or column comment set to an empty string would
  cause autogenerate to detect a comment change on every run. As most
  backends, including PostgreSQL, MySQL, MariaDB and Oracle, don't store an
  empty string comment distinctly from no comment, autogenerate now treats
  an empty string comment the same as None when comparing comments.
  Additionally, an empty string comment is now rendered in
  op.create_table() and op.add_column() directives, where it was
  previously omitted. Pull request courtesy vineoy.

  References: #1085

• [bug] [autogenerate] [postgresql] Fixed rendering of the PostgreSQL
  ~sqlalchemy.dialects.postgresql.DOMAIN type in autogenerated
  migration scripts. Previously the type was rendered using repr(),
  which omitted the check, not_null, default, collation,
  constraint_name, schema and create_type arguments and did not
  apply a dialect prefix to the underlying data type. The full set of
  arguments is now rendered and the underlying data type is rendered using
  the standard type-rendering logic. Pull request courtesy Sebastian Cao.

  References: #1360

• [bug] [autogenerate] [postgresql] Fixed false-positive "Computed default cannot be modified" warning emitted
  during autogenerate when comparing PostgreSQL Computed columns
  whose reflected SQL expression includes type cast specifiers such as
  ::regconfig or ::text, which PostgreSQL adds to the expression as
  stored. These cast specifiers are now stripped before comparison so that
  otherwise equivalent expressions no longer trigger the warning. Pull
  request courtesy Sebastian Cao.

  References: #1462

• [bug] [autogenerate] [postgresql] Fixed issue where autogenerate would detect an unchanged PostgreSQL
  expression-based index as modified when the expression included type
  casts, such as a cast to a type with a length or precision, a nested
  cast, or a cast followed by a DESC modifier.

• [bug] [postgresql] Fixed bug where Operations.alter_column() against a PostgreSQL
  identity column would render an incomplete, invalid ALTER TABLE ... ALTER COLUMN statement with no clause at all when existing_server_default
  was omitted, even if there were no existing server default. Pull request
  courtesy Riti Grover.

  References: #1504

• [bug] [environment] Fixed issue where a third party plugin published using the
  alembic.plugins entrypoint, configured to refer to a plugin module as
  documented at alembic.plugins.toplevel, would cause import alembic to fail with a TypeError, as the loaded module was
  erroneously iterated rather than being set up directly. An entrypoint
  that refers to a collection of modules, the form which inadvertently
  worked previously, continues to be accepted but now emits a deprecation
  warning.

  References: #1873

• [bug] [autogenerate] Fixed issue where dialect-specific keyword arguments on a
  ForeignKeyConstraint, ForeignKey or
  CheckConstraint, such as postgresql_not_valid, were not
  rendered for the constraints that are part of an autogenerated
  Operations.create_table() directive, nor for an autogenerated
  Operations.create_check_constraint() directive. The
  Operations.create_table() case additionally requires SQLAlchemy
  2.0.55 / 2.1.5 or greater, which include the fix for SQLAlchemy issue
  #13677 where these arguments were lost when the Table was
  copied.

  References: #1876

• [bug] [autogenerate] Fixed issue where, when using SQLAlchemy 2.1, the CHECK constraint
  generated by a type such as ~sqlalchemy.types.Enum or
  ~sqlalchemy.types.Boolean with create_constraint=True would
  be rendered by autogenerate as explicit sa.CheckConstraint() entries
  within op.create_table(), in addition to the type itself which
  already produces that constraint, leading to a duplicate constraint error
  when the migration is run.

  References: #1884

• [bug] [operations] Fixed issue where a CreateTableOp produced from an existing
  ~sqlalchemy.schema.Table using CreateTableOp.from_table()
  would emit the CHECK constraint generated by a type such as
  ~sqlalchemy.types.Enum or ~sqlalchemy.types.Boolean
  with create_constraint=True twice in the resulting CREATE TABLE
  statement when invoked directly.