def build_parent_relationship(self):
"""
Builds a relationship between currently built history class and
parent class (the model whose history the currently build history
class represents).
"""
conditions = []
foreign_keys = []
for primary_key in primary_keys(self.model):
conditions.append(
getattr(self.model, primary_key.name)
==
getattr(self.extension_class, primary_key.name)
)
foreign_keys.append(
getattr(self.extension_class, primary_key.name)
)
# We need to check if versions relation was already set for parent
# class.
if not hasattr(self.model, 'versions'):
self.model.versions = sa.orm.relationship(
self.extension_class,
primaryjoin=sa.and_(*conditions),
foreign_keys=foreign_keys,
lazy='dynamic',
backref=sa.orm.backref(
'version_parent'
),
viewonly=True
)
def build_foreign_key(self):
names = [column.name for column in primary_keys(self.model)]
return sa.schema.ForeignKeyConstraint(
names,
[
'%s.%s' % (self.model.__tablename__, name)
for name in names
],
ondelete='CASCADE'
)
def build_reflected_primary_keys(self):
columns = []
for column in primary_keys(self.model):
# Make a copy of the column so that it does not point to wrong
# table.
column_copy = column.copy()
# Remove unique constraints
column_copy.unique = False
columns.append(column_copy)
return columns