implicit /

#    Copyright 2011 Dexetra <>

#    This program is free software: you can redistribute it and/or modify
#    it under the terms of the GNU General Public License as published by
#    the Free Software Foundation, either version 3 of the License, or
#    (at your option) any later version.

#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    GNU General Public License for more details.

#    You should have received a copy of the GNU General Public License
#    along with this program.  If not, see <>.

from sqlalchemy.schema import ForeignKeyConstraint, Column
from sqlalchemy.event import listen

class ImplicitForeignKeyConstraint(ForeignKeyConstraint):

    def __init__(self, columns, refcolumns, primary_key=None, **kwargs):
        super(ImplicitForeignKeyConstraint, self).__init__(
                columns, refcolumns, **kwargs)
        self.primary_key_flag = primary_key

    def _add_columns(constraint, table):
	referenced_table = table.metadata.tables[
	for column, element in zip(constraint.columns, constraint.elements):
	    new_column = getattr(
		    element.target_fullname.split('.')[1]).copy() = column
	    new_column.key = column
	    if constraint.primary_key_flag is not None:
		new_column.primary_key = constraint.primary_key_flag

listen(ImplicitForeignKeyConstraint, "before_parent_attach", ImplicitForeignKeyConstraint._add_columns)

def example_main():
    from sqlalchemy.schema import Column, Table
    from sqlalchemy.types import Integer
    from sqlalchemy.engine import create_engine
    from sqlalchemy.ext.declarative import declarative_base
    from implicit import ImplicitForeignKeyConstraint
    Base = declarative_base(bind=create_engine('sqlite://', echo=True))
    class A(Base):
        __tablename__ = 'a'
        id = Column(Integer, primary_key=True)
    class B(Base):
        __tablename__ = 'b'
        #id = Column(Integer, primary_key=True, autoincrement=False)
        __table_args__ = (ImplicitForeignKeyConstraint(['a_id'], ['']),)
    t = (Table(
            'c', Base.metadata,
            #Column('id', Integer, primary_key=True, autoincrement=False),
            ImplicitForeignKeyConstraint(['id'], [''], primary_key=False)))

if __name__ == "__main__":
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