diff options
Diffstat (limited to 'lib/sqlalchemy/sql')
| -rw-r--r-- | lib/sqlalchemy/sql/ddl.py | 57 | ||||
| -rw-r--r-- | lib/sqlalchemy/sql/schema.py | 32 |
2 files changed, 66 insertions, 23 deletions
diff --git a/lib/sqlalchemy/sql/ddl.py b/lib/sqlalchemy/sql/ddl.py index 51526173f..569030651 100644 --- a/lib/sqlalchemy/sql/ddl.py +++ b/lib/sqlalchemy/sql/ddl.py @@ -949,7 +949,9 @@ class SchemaDropper(DDLBase): self.connection.execute(DropSequence(sequence)) -def sort_tables(tables, skip_fn=None, extra_dependencies=None): +def sort_tables( + tables, skip_fn=None, extra_dependencies=None, +): """sort a collection of :class:`_schema.Table` objects based on dependency . @@ -963,16 +965,29 @@ def sort_tables(tables, skip_fn=None, extra_dependencies=None): .. warning:: - The :func:`.sort_tables` function cannot by itself accommodate - automatic resolution of dependency cycles between tables, which - are usually caused by mutually dependent foreign key constraints. - To resolve these cycles, either the - :paramref:`_schema.ForeignKeyConstraint.use_alter` - parameter may be applied - to those constraints, or use the - :func:`_expression.sort_tables_and_constraints` - function which will break - out foreign key constraints involved in cycles separately. + The :func:`._schema.sort_tables` function cannot by itself + accommodate automatic resolution of dependency cycles between + tables, which are usually caused by mutually dependent foreign key + constraints. When these cycles are detected, the foreign keys + of these tables are omitted from consideration in the sort. + A warning is emitted when this condition occurs, which will be an + exception raise in a future release. Tables which are not part + of the cycle will still be returned in dependency order. + + To resolve these cycles, the + :paramref:`_schema.ForeignKeyConstraint.use_alter` parameter may be + applied to those constraints which create a cycle. Alternatively, + the :func:`_schema.sort_tables_and_constraints` function will + automatically return foreign key constraints in a separate + collection when cycles are detected so that they may be applied + to a schema separately. + + .. versionchanged:: 1.3.17 - a warning is emitted when + :func:`_schema.sort_tables` cannot perform a proper sort due to + cyclical dependencies. This will be an exception in a future + release. Additionally, the sort will continue to return + other tables not involved in the cycle in dependency order + which was not the case previously. :param tables: a sequence of :class:`_schema.Table` objects. @@ -990,7 +1005,7 @@ def sort_tables(tables, skip_fn=None, extra_dependencies=None): :func:`.sort_tables_and_constraints` - :meth:`_schema.MetaData.sorted_tables` - uses this function to sort + :attr:`_schema.MetaData.sorted_tables` - uses this function to sort """ @@ -1010,14 +1025,17 @@ def sort_tables(tables, skip_fn=None, extra_dependencies=None): return [ t for (t, fkcs) in sort_tables_and_constraints( - tables, filter_fn=_skip_fn, extra_dependencies=extra_dependencies + tables, + filter_fn=_skip_fn, + extra_dependencies=extra_dependencies, + _warn_for_cycles=True, ) if t is not None ] def sort_tables_and_constraints( - tables, filter_fn=None, extra_dependencies=None + tables, filter_fn=None, extra_dependencies=None, _warn_for_cycles=False ): """sort a collection of :class:`_schema.Table` / :class:`_schema.ForeignKeyConstraint` @@ -1101,9 +1119,20 @@ def sort_tables_and_constraints( ) ) except exc.CircularDependencyError as err: + if _warn_for_cycles: + util.warn( + "Cannot correctly sort tables; there are unresolvable cycles " + 'between tables "%s", which is usually caused by mutually ' + "dependent foreign key constraints. Foreign key constraints " + "involving these tables will not be considered; this warning " + "may raise an error in a future release." + % (", ".join(sorted(t.fullname for t in err.cycles)),) + ) for edge in err.edges: if edge in mutable_dependencies: table = edge[1] + if table not in err.cycles: + continue can_remove = [ fkc for fkc in table.foreign_key_constraints diff --git a/lib/sqlalchemy/sql/schema.py b/lib/sqlalchemy/sql/schema.py index b7ac16b0a..08dc487d4 100644 --- a/lib/sqlalchemy/sql/schema.py +++ b/lib/sqlalchemy/sql/schema.py @@ -4087,15 +4087,29 @@ class MetaData(SchemaItem): .. warning:: - The :attr:`.sorted_tables` accessor cannot by itself accommodate - automatic resolution of dependency cycles between tables, which - are usually caused by mutually dependent foreign key constraints. - To resolve these cycles, either the - :paramref:`_schema.ForeignKeyConstraint.use_alter` - parameter may be - applied to those constraints, or use the - :func:`_schema.sort_tables_and_constraints` function which will - break out foreign key constraints involved in cycles separately. + The :attr:`.MetaData.sorted_tables` attribute cannot by itself + accommodate automatic resolution of dependency cycles between + tables, which are usually caused by mutually dependent foreign key + constraints. When these cycles are detected, the foreign keys + of these tables are omitted from consideration in the sort. + A warning is emitted when this condition occurs, which will be an + exception raise in a future release. Tables which are not part + of the cycle will still be returned in dependency order. + + To resolve these cycles, the + :paramref:`_schema.ForeignKeyConstraint.use_alter` parameter may be + applied to those constraints which create a cycle. Alternatively, + the :func:`_schema.sort_tables_and_constraints` function will + automatically return foreign key constraints in a separate + collection when cycles are detected so that they may be applied + to a schema separately. + + .. versionchanged:: 1.3.17 - a warning is emitted when + :attr:`.MetaData.sorted_tables` cannot perform a proper sort + due to cyclical dependencies. This will be an exception in a + future release. Additionally, the sort will continue to return + other tables not involved in the cycle in dependency order which + was not the case previously. .. seealso:: |