Add get_referencing_foreign_keys

CHANGES.rst

@@ -4,6 +4,12 @@ Changelog
 Here you can see the full list of changes between each SQLAlchemy-Utils release.
 
 
+0.25.5 (2014-xx-xx)
+^^^^^^^^^^^^^^^^^^^
+
+- Added get_referencing_foreign_keys
+
+
 0.25.4 (2014-04-22)
 ^^^^^^^^^^^^^^^^^^^
 

docs/model_helpers.rst

@@ -28,6 +28,12 @@ get_primary_keys
 .. autofunction:: primary_keys
 
 
+get_referencing_foreign_keys
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+.. autofunction:: get_referencing_foreign_keys
+
+
 query_entities
 ^^^^^^^^^^^^^^
 

sqlalchemy_utils/__init__.py

@@ -13,6 +13,7 @@ from .functions import (
     get_columns,
     get_declarative_base,
     get_primary_keys,
+    get_referencing_foreign_keys,
     identity,
     mock_engine,
     naturally_equivalent,
@@ -80,6 +81,7 @@ __all__ = (
     get_columns,
     get_declarative_base,
     get_primary_keys,
+    get_referencing_foreign_keys,
     identity,
     instrumented_list,
     merge,

sqlalchemy_utils/functions/__init__.py

@@ -15,6 +15,7 @@ from .orm import (
     get_columns,
     get_declarative_base,
     get_primary_keys,
+    get_referencing_foreign_keys,
     getdotattr,
     has_changes,
     identity,
@@ -33,6 +34,7 @@ __all__ = (
     'get_columns',
     'get_declarative_base',
     'get_primary_keys',
+    'get_referencing_foreign_keys',
     'getdotattr',
     'has_changes',
     'identity',

sqlalchemy_utils/functions/orm.py

@@ -14,6 +14,35 @@ from sqlalchemy.orm.query import _ColumnEntity
 from sqlalchemy.orm.util import AliasedInsp
 
 
+def get_referencing_foreign_keys(mixed):
+    """
+    Returns referencing foreign keys for given Table object or declarative
+    class.
+
+    :param mixed:
+        SA Table object or SA declarative class
+
+    ::
+
+        get_foreign_keys(User)  # set([ForeignKey('user.id')])
+    """
+    if isinstance(mixed, sa.Table):
+        tables = [mixed]
+    else:
+        # TODO: make this support joined table inheritance
+        tables = [mixed.__table__]
+
+    referencing_foreign_keys = set()
+
+    for table in mixed.metadata.tables.values():
+        for constraint in table.constraints:
+            if isinstance(constraint, sa.sql.schema.ForeignKeyConstraint):
+                for fk in constraint.elements:
+                    if any(fk.references(t) for t in tables):
+                        referencing_foreign_keys.add(fk)
+    return referencing_foreign_keys
+
+
 def get_primary_keys(mixed):
     """
     Return an OrderedDict of all primary keys for given Table object,

tests/__init__.py

@@ -38,7 +38,7 @@ class TestCase(object):
 
     def setup_method(self, method):
         self.engine = create_engine(self.dns)
-        self.engine.echo = True
+        # self.engine.echo = True
         self.connection = self.engine.connect()
         self.Base = declarative_base()