i think this should be it: http://www.sqlalchemy.org/docs/04/plugins.html#plugins_associationproxy
and relevant discussion here: http://groups.google.com/group/sqlalchemy/browse_thread/thread/52565295f54fd85/31f53dca1e31e5ee?hl=en&lnk=gst&q=mapper+for+two+tables#31f53dca1e31e5ee On Oct 2, 3:50 pm, rca <[EMAIL PROTECTED]> wrote: > Thanks again, it is much appreciated > > On Oct 2, 1:03 pm, [EMAIL PROTECTED] wrote: > > > if the tables have nothing in common, u can have a MapperExtension > > that when touching one item updates the proper table. > > as a working big example, > > see sqlalachemyAggregator, either inhttp://dev.gafol.net/t/aggregator > > orhttp://dbcook.svn.sourceforge.net/viewvc/dbcook/trunk/dbcook/misc/agg... > > which does things like counting summing etc > > runtime-updates-of-some-cache. > > but i'm not sure if that is what u want; imo u need it more explicit > > than this.. > > I have the same feeling (much less assertive here, me, the sql/alchemy > noop) > but i will study the example > > > > > and i still cant see how obj.surface=xyz will lookup and populate > > surface_id. imo u need 3 attributes: > > - _surface_text - table1.surface, hidden > > - _surface_id - table2.surface, hidden > > - surface: property which is visible and does the dispatch/lookup etc > > yes, the three attributes, i am able to do this now - what I am unable > is to map them to different tables -- and be persisted when > session.save(obj) -- and > session.query(obj).filter(obj.attribute_from_the_second_table) > It must be something stupid, i will try to come with an example > > > > > ciao > > > On Thursday 02 October 2008 13:59:40 rca wrote: > > > > thanks for the pointer, I tried and finally managed something the > > > synonym (with the big neon "don't panic" in my head) > > > > I can do the conversion and insert "integers id" in place of > > > "textual representation" and when accessing the parameter .surface, > > > get the textual representation instead of id > > > In this way, it works the same as my own type, but just more > > > flexible (it can access other parameters of the object). > > > > But still... is there a way to map one class to two tables in one > > > go? > > > > To have : > > > obj.surface_id --> table1.surface_id > > > obj.surface --> table2.surface > > > > when you do: > > > obj.surface = "XXX" > > > obj.name="YYY" > > > to have sqlachemy do: > > > "UPDATE table2 SET surface='XXX' WHERE table2.id = 2" (this is a > > > foreign key, the value is in the table1.surface_id) > > > *AND* > > > "UPDATE table1 SET name='YYY' WHERE table1.id = 8" > > > > i am getting this, which is wrong, because surface is foreign key, > > > an integer: > > > SELECT s1.* FROM table1 AS s1 WHERE s2.surface_id = 'XXX' > > > > if using the custom type, i am able to translate the attribute to > > > its id, and use it in the query, yet the synonym might be better, > > > only if it was possible to do > > > session.query(Object).filter(Object.surface== "XXX") > > > and get: SELECT s1.*, s2.* FROM table1 AS s1 LEFT JOIN table2 AS s2 > > > ON s1.surface_id = s2.id WHERE s2.surface = 'XXX' > > > > remember, my goal was to use obj.surface = "XXX" and have this > > > value referenced from the other table. > > > > Sorry if my questions are stupid! > > > > --roman > > > > On Oct 1, 10:21 am, [EMAIL PROTECTED] wrote: > > > > maybe try, instead of hiding the conversion inside db-types > > > > layer, to move it upper, i.e. make it a real reference/FK-column > > > > to real object/table, then make a python property (see "synonim") > > > > to do the conversion. > > > > > On Tuesday 30 September 2008 23:20:16 rca wrote: > > > > > Hi all, > > > > > > my apologies for a long question, I am new to sqlalchemy and I > > > > > was struggling with one problem. I solved it but I really not > > > > > sure it's the right way to do it. > > > > > > The problem is that I need to create objects like this: > > > > > Token(pos=2, surface="helloWorld") > > > > > > The surface is string, but in the database, it should be saved > > > > > as reference to an other table (looked-up and saved if not > > > > > existing) > > > > > > The way I solved it was to create my own column type decorating > > > > > Integer. On the way in, it gets text and stores id, on the way > > > > > out, it gives the text back. > > > > > > But I don't know if my solution is safe. For instance, > > > > > -- I am decorating Integer type, but on the output there is > > > > > string. -- I am using the EntitySingleton recipy, but I found > > > > > out I could not use the recommended > > > > > Session = scoped_session(sessionmaker()) > > > > > I had to say: Session = sessionmaker() > > > > > -- And I do commit for every new looked-up value > > > > > > And also, I have the impression the solution is very > > > > > complicated, perhaps you could help me to do it in a better > > > > > way. > > > > > > Many thanks! > > > > > > roman > > > > > > Here is the code with an example: > > > > > ------------------------------------------------------- > > > > > > import sqlalchemy as sa > > > > > from sqlalchemy.ext.declarative import declarative_base > > > > > from sqlalchemy.orm import scoped_session, sessionmaker, > > > > > relation, backref, mapper > > > > > from sqlalchemy import create_engine, Table, Column, Integer, > > > > > String, MetaData, ForeignKey > > > > > #from mimetypes import types_map > > > > > import weakref > > > > > import sqlalchemy.types as types > > > > > > Session = sessionmaker() #scoped_session(sessionmaker) > > > > > > DBase = declarative_base() > > > > > > class MyUnique(types.TypeDecorator): > > > > > """a type that decorates Integer, > > > > > receives a text representation - eg. MyValueFromEnumeration > > > > > and replaces it in the database with id of the string above > > > > > It makes sure that inserted values are unique (creates them > > > > > if not exist)""" > > > > > > impl = types.Integer > > > > > > def process_bind_param(self, value, dialect): > > > > > #ukladani do databaze > > > > > if not hasattr(self, '__unique_valuee'): > > > > > self.__unique_valuee = Surface(value) > > > > > return self.__unique_valuee.id > > > > > > def process_result_value(self, value, dialect): > > > > > #vystup > > > > > return self.__unique_valuee.surface > > > > > > """ #if it is string type > > > > > def copy(self): > > > > > return MyUniqueString(self.impl.length) > > > > > """ > > > > > > class DocumentBase(object): > > > > > def __init__(self): > > > > > self.metadata = DBase.metadata > > > > > self.engine = None > > > > > > def open(self, url='sqlite:///:memory:'): > > > > > self.engine = create_engine(url, echo=True) > > > > > #engine = create_engine('sqlite:///' + __file__ + > > > > > ".db", echo=True) > > > > > Session.configure(bind=self.engine) > > > > > self.metadata.bind = self.engine > > > > > > surface_table = sa.Table('surface', self.metadata, > > > > > sa.Column('id', sa.Integer, primary_key=True, > > > > > autoincrement=True), > > > > > sa.Column('surface', sa.String(500), > > > > > autoincrement=True) ) > > > > > > mapper(Surface, surface_table) > > > > > > self.metadata.create_all(checkfirst=True) > > > > > > def add(self, document_object): > > > > > sess = Session() > > > > > sess.save_or_update(document_object) > > > > > sess.commit() > > > > > > class EntitySingleton(type): > > > > > """a metaclass that insures the creation of unique and non- > > > > > existent entities for > > > > > a particular constructor argument. if an entity with a > > > > > particular constructor > > > > > argument was already created, either in memory or in the > > > > > database, it is returned > > > > > in place of constructing the new instance.""" > > > > > > def __init__(cls, surface, bases, dct): > > > > > cls.instances = weakref.WeakValueDictionary() > > > > > > def __call__(cls, surface): > > > > > session = Session() > > > > > > hashkey = surface > > > > > try: > > > > > return cls.instances[hashkey] > > > > > except KeyError: > > > > > instance = > > > > > session.query(cls).filter(cls.surface==surface).first() > > > > > if instance is None: > > > > > instance = type.__call__(cls, surface) > > > > > #session.begin_nested() > > > > > session.add(instance) > > > > > session.commit() > > > > > # optional - flush the instance when it's saved > > > > > session.flush([instance]) > > > > > cls.instances[hashkey] = instance > > > > > return instance > > > > > > class Document(DBase): > > > > > __tablename__ = 'documents' > > > > > id = sa.Column(sa.Integer(9), primary_key=True, > > > > > autoincrement=True) > > > > > name = sa.Column(sa.String(500)) > > > > > uri = sa.Column(sa.String(500)) > > > > > processing_stage = sa.Column(sa.String(500)) > > > > > > tokens = relation("Token", backref="Document") > > > > > > def __xinit__(self, name): > > > > > self.name = name > > > > > def __repr__(self): > > > > > return "<%s('%s','%s')>" % (self.__class__, self.id, > > > > > self.name) > > > > > > class Token(DBase): > > > > > __tablename__ = 'tokens' > > > > > id = sa.Column(sa.Integer(6), primary_key=True, > > > > > autoincrement=True) > > > > > pos = sa.Column(sa.Integer(6)) > > > > > type = sa.Column(sa.String(500)) > > > > > surface = sa.Column(MyUnique(500), > > > > > sa.ForeignKey('surface.id')) surface_translated = > > > > > sa.Column(sa.String(500)) > > > > > sem = sa.Column(sa.String(500)) > > > > > > title_id = sa.Column(sa.Integer, > > > > > sa.ForeignKey('documents.id')) #document = relation("Document", > > > > > backref="Token") > > > > > > #def __init__(self, surface=None, **kwargs): > > > > > > def __repr__(self): > > ... > > read more » --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "sqlalchemy" group. 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