[sqlalchemy] Re: Get default value
Em Sex, 2008-01-11 às 08:54 +0200, [EMAIL PROTECTED] escreveu:
either put the correct polymorphic_on=resource.c.poly, or remove it
alltogether,
it comes from the inherited base-mapper.
Exactly, works fine leaving poly on resource and mapping all
polymorphic_on=resource.c.poly
cookbook helps me to, but just this change make my model working
Thank you a lot, and thank's to all replies.
follow the correct mapping to anyone wants:
-code---8--code-
from sqlalchemy import create_engine, MetaData, Table, Column, types, ForeignKey
from sqlalchemy.orm import mapper, relation, backref, create_session
from sqlalchemy.sql.expression import outerjoin, join
from sqlalchemy import String, Unicode, Integer, DateTime, Numeric, Boolean,
UnicodeText
db = create_engine('sqlite:///sa.db')
metadata = MetaData()
metadata = MetaData(db)
metadata.bind = db
session = create_session(bind=db)
resource_table = Table('resource', metadata,
Column('id',Integer, primary_key=True),
Column('name', String(30)),
Column('poly', String(31), nullable=True)
)
person_table = Table('person', metadata,
Column('id',Integer, ForeignKey('resource.id'), primary_key=True,),
)
material_table = Table('material', metadata,
Column('id',Integer, ForeignKey('resource.id'), primary_key=True,),
)
employee_table = Table('employee', metadata,
Column('id',Integer, ForeignKey('person.id'), primary_key=True),
)
technical_table = Table('technical', metadata,
Column('id',Integer, ForeignKey('person.id'), primary_key=True),
)
class Resource(object):
def __init__(self, name):
self.name = name
def __repr__(self):
return Resource id=%d ,name=%s % (self.id,self.name)
class Person(Resource):
def __repr__(self):
return Person id=%d ,name=%s % (self.id,self.name)
class Material(Resource):
def __repr__(self):
return Material id=%d ,name=%s % (self.id,self.name)
class Employee(Person):
def __repr__(self):
return Employee id=%d ,name=%s % (self.id,self.name)
class Technical(Person):
def __repr__(self):
return Technical id=%d ,name=%s % (self.id,self.name)
mapper(Resource, resource_table,
polymorphic_on=resource_table.c.poly,
polymorphic_identity='resource',
)
mapper(Person, person_table,
inherits=Resource, polymorphic_identity='person',
polymorphic_on= resource_table.c.poly,
)
mapper(Material, material_table,
inherit_condition= material_table.c.id == resource_table.c.id,
inherits=Resource, polymorphic_identity='material'
)
mapper(Employee, employee_table,
inherit_condition= employee_table.c.id == person_table.c.id,
inherits=Person, polymorphic_identity='employee',
)
mapper(Technical, technical_table,
inherit_condition= technical_table.c.id == person_table.c.id,
inherits=Person, polymorphic_identity='technical',
)
metadata.create_all(bind=db)
r = Resource('resource name')
p = Person('person name')
m = Material('material name')
e = Employee('employee name')
t = Technical('technical name')
session.save(r)
session.save(p)
session.save(m)
session.save(e)
session.save(t)
session.flush()
session.clear()
print LIST FROM RESOURCES #
for o in session.query(Resource).all():
print o, o.poly
print LIST FROM PERSONS #
for o in session.query(Person).all():
print o, o.poly
-code---8--code-
results are:
LIST FROM RESOURCES #
Resource id=1 ,name=resource name resource
Person id=2 ,name=person name person
Material id=3 ,name=material name material
Employee id=4 ,name=employee name employee
Technical id=5 ,name=technical name technical
LIST FROM PERSONS #
Person id=2 ,name=person name person
Employee id=4 ,name=employee name employee
Technical id=5 ,name=technical name technical
Thanks again,
Att
--
Alexandre da Silva
Analista de Sistemas - Bacharel em Sistemas de Informação (2003-2007)
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[sqlalchemy] Re: Get default value
Isn't it just column.default ? --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalchemy@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en -~--~~~~--~~--~--~---
[sqlalchemy] Re: Get default value
Ah, I read too fast, you are getting back the ColumnDefault object try column.default.arg --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalchemy@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en -~--~~~~--~~--~--~---
[sqlalchemy] Re: Get default value
Alexandre da Silva wrote: Hello all, is there a way that I can get the default value defined on Column(default=something) ? the default I get is a ColumDefault, and I don't know how to get it's value. any suggestion? The value is in its .arg property: col.default.arg --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalchemy@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en -~--~~~~--~~--~--~---
[sqlalchemy] Re: Get default value
Em Qui, 2008-01-10 às 17:13 -0800, jason kirtland escreveu:
col.default.arg
Yes, exactly this.
another question
How many levels I can inherit classes/tables without get something
wrong?
let me show a simplest sample hierarchy:
resource
/ \
person material
/ \
employeecustomer
now, I am creating a type column on resource to map persons and
materials, them I am creating another type column on person, to get
mapped the various types of persons.
by this way, I could get a employee instance, just selecting a resource
but something is going wrong, because the column type on resource is not
filled with correct value, and I am getting NOT NULL CONSTRAINT by
insert an employee.
the tables
resource_table = Table(
Column('id',Integer, primary_key=True),
Column('poly', String(31), nullable=False)
)
person_table = Table(
Column('id',Integer, primary_key=True, ForeignKey('resource.id'),
primary_key=True)),
Column('poly', String(31), nullable=False)
)
employee_table = Table(
Column('id',Integer, primary_key=True, ForeignKey('person.id'),
primary_key=True)),
)
the classes
class Resource(object):
pass
class Person(Resource):
pass
class Employee(Person):
pass
mappers
mapper(Resource, resource_table,
polymorphic_on=resource_table.c.poly,
polymorphic_identity='resource'
)
mapper(Person, person_table,
polymorphic_on=person_table.c.poly,
inherits=Resource, polymorphic_identity='person'
)
mapper(Employee employee_table,
inherits=Person, polymorphic_identity='employee',
)
is all, now when I create an instance of Employee and try to save, I get
back an integrity error, that resource.poly cannot be null
any suggestion?
thank's for previous replies.
--
Alexandre da Silva
Analista de Sistemas - Bacharel em Sistemas de Informação (2003-2007)
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[sqlalchemy] Re: Get default value
You're mixing single-table inheritance (using the discriminator column),
with concrete inheritance (using multiple tables).
You have to pick one scheme or the other. Either use a single inheritance
chain, or separate the two class hierarchies into two separate chains that
don't inherit from each other. In the separate scheme, each chain can use
it's own discriminator column, but you cannot combine two class hierarchies
that each use a different discriminator column.
On Jan 10, 2008 8:46 PM, Alexandre da Silva [EMAIL PROTECTED] wrote:
Em Qui, 2008-01-10 às 17:13 -0800, jason kirtland escreveu:
col.default.arg
Yes, exactly this.
another question
How many levels I can inherit classes/tables without get something
wrong?
let me show a simplest sample hierarchy:
resource
/ \
person material
/ \
employeecustomer
now, I am creating a type column on resource to map persons and
materials, them I am creating another type column on person, to get
mapped the various types of persons.
by this way, I could get a employee instance, just selecting a resource
but something is going wrong, because the column type on resource is not
filled with correct value, and I am getting NOT NULL CONSTRAINT by
insert an employee.
the tables
resource_table = Table(
Column('id',Integer, primary_key=True),
Column('poly', String(31), nullable=False)
)
person_table = Table(
Column('id',Integer, primary_key=True, ForeignKey('resource.id'),
primary_key=True)),
Column('poly', String(31), nullable=False)
)
employee_table = Table(
Column('id',Integer, primary_key=True, ForeignKey('person.id'),
primary_key=True)),
)
the classes
class Resource(object):
pass
class Person(Resource):
pass
class Employee(Person):
pass
mappers
mapper(Resource, resource_table,
polymorphic_on=resource_table.c.poly,
polymorphic_identity='resource'
)
mapper(Person, person_table,
polymorphic_on=person_table.c.poly,
inherits=Resource, polymorphic_identity='person'
)
mapper(Employee employee_table,
inherits=Person, polymorphic_identity='employee',
)
is all, now when I create an instance of Employee and try to save, I get
back an integrity error, that resource.poly cannot be null
any suggestion?
thank's for previous replies.
--
Alexandre da Silva
Analista de Sistemas - Bacharel em Sistemas de Informação (2003-2007)
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[sqlalchemy] Re: Get default value
Em Qui, 2008-01-10 às 21:20 -0500, Rick Morrison escreveu:
You're mixing single-table inheritance (using the discriminator
column), with concrete inheritance (using multiple tables).
You have to pick one scheme or the other. Either use a single
inheritance chain, or separate the two class hierarchies into two
separate chains that don't inherit from each other. In the separate
scheme, each chain can use it's own discriminator column, but you
cannot combine two class hierarchies that each use a different
discriminator column.
hum, so something is wrong here, I recreate a simple test case and all
is working properly, using the exactly model suggested on my previous
message. I will debug my application to find where is the error, but for
now, I don't know if this should work, but is working.
here is the test case and results:
code-8--code--
from sqlalchemy import create_engine, MetaData, Table, Column, types,
ForeignKey
from sqlalchemy.orm import mapper, relation, backref, create_session
from sqlalchemy import String, Unicode, Integer, DateTime, Numeric,
Boolean, UnicodeText
db = create_engine('sqlite:///:memory:')
metadata = MetaData()
metadata = MetaData(db)
metadata.bind = db
session = create_session(bind=db)
resource_table = Table('resource', metadata,
Column('id',Integer, primary_key=True),
Column('name', String(30)),
Column('poly', String(31), nullable=True)
)
person_table = Table('person', metadata,
Column('id',Integer, ForeignKey('resource.id'), primary_key=True,),
Column('poly', String(31), nullable=False)
)
material_table = Table('material', metadata,
Column('id',Integer, ForeignKey('resource.id'), primary_key=True,),
)
employee_table = Table('employee', metadata,
Column('id',Integer, ForeignKey('person.id'), primary_key=True),
)
technical_table = Table('technical', metadata,
Column('id',Integer, ForeignKey('person.id'), primary_key=True),
)
class Resource(object):
def __init__(self, name):
self.name = name
def __repr__(self):
return Resource id=%d ,name=%s % (self.id,self.name)
class Person(Resource):
def __repr__(self):
return Person id=%d ,name=%s % (self.id,self.name)
class Material(Resource):
def __repr__(self):
return Material id=%d ,name=%s % (self.id,self.name)
class Employee(Person):
def __repr__(self):
return Employee id=%d ,name=%s % (self.id,self.name)
class Technical(Person):
def __repr__(self):
return Technical id=%d ,name=%s % (self.id,self.name)
mapper(Resource, resource_table,
polymorphic_on=resource_table.c.poly,
polymorphic_identity='resource'
)
mapper(Person, person_table,
polymorphic_on=person_table.c.poly,
inherits=Resource, polymorphic_identity='person'
)
mapper(Material, material_table,
inherits=Resource, polymorphic_identity='material'
)
mapper(Employee, employee_table,
inherits=Person, polymorphic_identity='employee',
)
mapper(Technical, technical_table,
inherits=Person, polymorphic_identity='technical',
)
metadata.create_all(bind=db)
r = Resource('resource name')
p = Person('person name')
m = Material('material name')
e = Employee('employee name')
t = Technical('technical name')
session.save(r)
session.save(p)
session.save(m)
session.save(e)
session.save(t)
session.flush()
print LIST FROM RESOURCES #
for o in session.query(Resource).all():
print o
print LIST FROM PERSONS #
for o in session.query(Person).all():
print o
code-8--code--
The results:
LIST FROM RESOURCES #
Resource id=1 ,name=resource name
Person id=2 ,name=person name
Material id=3 ,name=material name
Employee id=4 ,name=employee name
Technical id=5 ,name=technical name
LIST FROM PERSONS #
Person id=2 ,name=person name
Employee id=4 ,name=employee name
Technical id=5 ,name=technical name
I think it is working properly.
but I will try to remove the type columns
Thank's for help
--
Alexandre da Silva
Analista de Sistemas - Bacharel em Sistemas de Informação (2003-2007)
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[sqlalchemy] Re: Get default value
Em Qui, 2008-01-10 às 21:20 -0500, Rick Morrison escreveu: You're mixing single-table inheritance (using the discriminator column), with concrete inheritance (using multiple tables). You have to pick one scheme or the other. Either use a single inheritance chain, or separate the two class hierarchies into two separate chains that don't inherit from each other. In the separate scheme, each chain can use it's own discriminator column, but you cannot combine two class hierarchies that each use a different discriminator column. In fact I am doing what is sugested here: http://www.sqlalchemy.org/docs/04/mappers.html#advdatamapping_mapper_inheritance_joined It works fine with one level inheritance class-subclass but the third subclassing don't working, it was because objects was in cache... savint to db and tryin to load again the identity is lost. how do you suggest to I do this? or I cannot? -- Alexandre da Silva Analista de Sistemas - Bacharel em Sistemas de Informação (2003-2007) --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalchemy@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en -~--~~~~--~~--~--~---
[sqlalchemy] Re: Get default value
How many levels I can inherit classes/tables without get something
wrong?
my tests go to 4, all works. And as all corner cases are already there,
i guess any level above will work too.
mixed inheritance (joined+concrete) also can be made to work, as long as
polymoprhic_union() is fixed slightly - AND no real polymoprhism over
concrete tables, that does not work on SA level / conceptualy.
may i suggest, that u get dbcook.sf.net, model your whole hierarchy there
(it is SIMPLE), then run it in generator mode (see usage/example/*) and see
what equivalent SA source/calls it generates.
maybe you are missing something (some mapper/relation parameters are tricky
to guess). be ware, only joined_inheritance is of real use (single_table is
not implemented).
let me show a simplest sample hierarchy:
resource
/ \
person material
/ \
employeecustomer
now, I am creating a type column on resource to map persons and
materials, them I am creating another type column on person, to get
mapped the various types of persons.
no u dont do it this way. u musthave only one discriminator column per
hierarchy-island.
either use the root one, and put all types there, or separate the material
from resource in its own subhierarchy. If there is explosion of types, to
avoid the huuuge union/outerjoin, u can make the resource a virtual base,
that is, not a table at all - so u'll have two separate db-hierarchies, each
one with its own root/discriminator. (dbcook: just declare
DBCOOK_no_mapping=True there.)
resource_table = Table(
Column('id',Integer, primary_key=True),
Column('poly', String(31), nullable=False)
)
person_table = Table(
Column('id',Integer, primary_key=True, ForeignKey('resource.id'),
primary_key=True)),
Column('poly', String(31), nullable=False)
)
u should not have poly here. its already in the root=resource.
employee_table = Table(
Column('id',Integer, primary_key=True, ForeignKey('person.id'),
primary_key=True)),
)
class Resource(object):
pass
class Person(Resource):
pass
class Employee(Person):
pass
mapper(Resource, resource_table,
polymorphic_on=resource_table.c.poly,
polymorphic_identity='resource'
)
mapper(Person, person_table,
polymorphic_on=person_table.c.poly,
inherits=Resource, polymorphic_identity='person'
)
either put the correct polymorphic_on=resource.c.poly, or remove it
alltogether,
it comes from the inherited base-mapper.
mapper(Employee employee_table,
inherits=Person, polymorphic_identity='employee',
)
svilen
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