Function sort_tables_and_constraints

lib/sqlalchemy/sql/ddl.py:1795–1928

Sort a collection of :class:`_schema.Table` / :class:`_schema.ForeignKeyConstraint` objects. This is a dependency-ordered sort which will emit tuples of ``(Table, [ForeignKeyConstraint, ...])`` such that each :class:`_schema.Table` follows its dependent :class:`_schema.Table`

(
    tables, filter_fn=None, extra_dependencies=None, _warn_for_cycles=False
)

@util.preload_module("sqlalchemy.sql.schema")
def sort_tables_and_constraints(
    tables, filter_fn=None, extra_dependencies=None, _warn_for_cycles=False
):
    """Sort a collection of :class:`_schema.Table`  /
    :class:`_schema.ForeignKeyConstraint`
    objects.

    This is a dependency-ordered sort which will emit tuples of
    ``(Table, [ForeignKeyConstraint, ...])`` such that each
    :class:`_schema.Table` follows its dependent :class:`_schema.Table`
    objects.
    Remaining :class:`_schema.ForeignKeyConstraint`
    objects that are separate due to
    dependency rules not satisfied by the sort are emitted afterwards
    as ``(None, [ForeignKeyConstraint ...])``.

    Tables are dependent on another based on the presence of
    :class:`_schema.ForeignKeyConstraint` objects, explicit dependencies
    added by :meth:`_schema.Table.add_is_dependent_on`,
    as well as dependencies
    stated here using the :paramref:`~.sort_tables_and_constraints.skip_fn`
    and/or :paramref:`~.sort_tables_and_constraints.extra_dependencies`
    parameters.

    :param tables: a sequence of :class:`_schema.Table` objects.

    :param filter_fn: optional callable which will be passed a
     :class:`_schema.ForeignKeyConstraint` object,
     and returns a value based on
     whether this constraint should definitely be included or excluded as
     an inline constraint, or neither.   If it returns False, the constraint
     will definitely be included as a dependency that cannot be subject
     to ALTER; if True, it will **only** be included as an ALTER result at
     the end.   Returning None means the constraint is included in the
     table-based result unless it is detected as part of a dependency cycle.

    :param extra_dependencies: a sequence of 2-tuples of tables which will
     also be considered as dependent on each other.

    .. seealso::

        :func:`.sort_tables`


    """
    Table = util.preloaded.sql_schema.Table

    fixed_dependencies = set()
    mutable_dependencies = set()

    if extra_dependencies is not None:
        fixed_dependencies.update(extra_dependencies)

    remaining_fkcs = set()
    for table in tables:
        for fkc in table.foreign_key_constraints:
            if fkc.use_alter is True:
                remaining_fkcs.add(fkc)