if it's about concrete inheritance, then employee contains ALL info it
needs, that is, a full copy of person + whatever else is there,
and is completely independent from person table.
so for that case,
a) foregn key is not needed
b) inserting in employee_tbl will never insert stuff in person_tbl - they
are independent.
now, what u're expecting (chaining of id's and rows etc) will come from
joined_table inheritance. See about that in docs; and just remove
concrete=True from your mapper.
Partha wrote:
> I have 2 tables Person (id, name) & Employee (id, salary) and every
> Employee 'isa' Person, so employee.id == person.id. I am trying to use
> the Concrete Inheritance (i.e. ' pjoin) example provided in the
> documentation. My mapping looks as follows.
>
> person_table = Table("persons", __meta__,
> Column("id", Integer, primary_key=True),
> Column("name", String(80))
> )
>
> employee_table = Table("empys", __meta__,
> Column("id", Integer, ForeignKey("persons.id"),
> primary_key=True),
> Column("salary", Integer),
> )
>
> class Person (object): pass
> class Employee(Person): pass
>
> pjoin = polymorphic_union({
> 'person':person_table,
> 'employee':employee_table
> }, 'type', 'pjoin')
>
>
>
> person_mapper = mapper(Person, person_table, select_table=pjoin, \
> polymorphic_on=pjoin.c.type,
> polymorphic_identity='person')
> emp_mapper = mapper(Employee, employee_table, inherits=person_mapper,
> \
> concrete=True, polymorphic_identity='employee')
>
>
>
> I want to now add a New employee to the system with the following
> snippet.
>
> e = Employee()
> e.name = 'TestEmpl'
> e.salary = 100
> session.save(e)
> session.commit()
>
> Problem is when it tries to save employee, sqlalchemy raises the
> following error
> """
> sqlalchemy.exceptions.ProgrammingError: (ProgrammingError) relation
> "empys_id_seq" does not exist
> 'select nextval(\'"empys_id_seq"\')' None
> """
> Since all id's in employees table map directly to Person table (which
> has the correct sequence), I would think alchemy would first store the
> "Person" part and then store the "employee" part. Any clues on how to
> correct this ??.
> I also tried adding a Sequence to employee forcing it to use the same
> one as person table...
>
> employee_table = Table("empys", __meta__,
> Column("id", Integer, ForeignKey("persons.id"),
> Sequence("person_id_seq") primary_key=True),
> Column("salary", Integer),
> )
>
>
> But now it raises a constraint violation because its trying to insert
> a row in employees table without inserting anything in person first..
>
> Any ideas how I can fix this?.. I would greatly appreciate any help in
> this regard.. Thanks
>
> Partha
>
>
> Here is the full program.. Thanks..
>
> from sqlalchemy import create_engine, MetaData, Table, Column, types,
> Sequence
> from sqlalchemy import Table, Column, Integer, String, DECIMAL,
> Numeric, ForeignKey, DateTime, Boolean, CHAR
> from sqlalchemy.orm import mapper,sessionmaker, relation,
> polymorphic_union
> __meta__ = MetaData()
>
> person_table = Table("persons", __meta__,
> Column("id", Integer, primary_key=True),
> Column("name", String(80))
> )
>
> employee_table = Table("empys", __meta__,
> Column("id", Integer, ForeignKey("persons.id"),
> primary_key=True),
> Column("salary", Integer),
> )
> class Person (object): pass
>
> class Employee(Person): pass
>
> pjoin = polymorphic_union({
> 'person':person_table,
> 'employee':employee_table
> }, 'type', 'pjoin')
>
>
>
> person_mapper = mapper(Person, person_table, select_table=pjoin, \
> polymorphic_on=pjoin.c.type,
> polymorphic_identity='person')
> emp_mapper = mapper(Employee, employee_table, inherits=person_mapper,
> \
> concrete=True, polymorphic_identity='employee')
>
>
> engine = create_engine('postgres:///test?user=postgres&password=foo',
> echo=True)
> session = sessionmaker(autoflush=True, bind = engine,
> transactional=True)()
>
> def refresh(engine = engine):
> __meta__.drop_all(engine)
> __meta__.create_all(engine)
>
> def main():
> refresh()
> e = Employee()
> e.name = 'TestEmpl'
> e.salary = 100
> session.save(e)
> session.commit()
>
> if __name__ == '__main__':
> main()
>
> >
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