[sqlalchemy] existing database/hibernating

[Gregor Kling]

Hello Alchemystas,

I have a legacy database, with a self written ORM not to fuss about.
So I want to use a some more intelligent mechanism - sqlalchemy.
I have written a little hibernator, that does nothing more, as to 
ask the database for its metadata via sqlalchemy (heron:0.4.2p3-1) 
and construct classes of the form:

from sqlalchemy import *
from sqlalchemy.orm import mapper

from dvzrv.db import sAmetaData

class SrvDomainTable(object):
   def __init__(self,domain_name=None,srv_id=None):
     self.sAtablename = 'srv_domain'
     self.sAsrv_domain_table = Table(self.sAtablename, sAmetaData, 
autoload=True)
     self.sAmapped_srv_domain = 
mapper(DVZsrvDomainTable,self.sAsrv_domain_table,primary_key=[self.sAsrv_domain_table.c.domain_name])

     self.domain_name = domain_name
     self.srv_id = srv_id

I still do not have clue, how to cope with association tables.
The class SrvDomainTable for example is one of those.
The usage of primary key is only to test functionality.
So my question is, will it suffice to use the primary key list 
listing all foreign keys -like this: 
primary_key=[self.sAsrv_domain_table.c.domain_name,self.sAsrv_domain_table.c.srv_id].
 
Or do I have to use it like the example in
http://www.sqlalchemy.org/docs/04/mappers.html ?
Regrettably I do not grasp the idea of the example up to now,


left_table = Table('left', metadata,
     Column('id', Integer, primary_key=True))

right_table = Table('right', metadata,
     Column('id', Integer, primary_key=True))

association_table = Table('association', metadata,
     Column('left_id', Integer, ForeignKey('left.id')),
     Column('right_id', Integer, ForeignKey('right.id')),
     )

mapper(Parent, left_table, properties={
     'children':relation(Child, secondary=association_table)
})

mapper(Child, right_table)


because it uses only the parent mapper to some things,
whereas the childmapper is unchanged..


thanks
gregor


-- 
Gregor Kling

Abteilung ITS, Sachgebiet DVZ
Fachhochschule Giessen
Tel: 0641/309-1292
E-Mail: [EMAIL PROTECTED]

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