[sqlalchemy] Re: Overriding table columns with Python-property
Michael Bayer wrote: well, i can support this in 0.5 trunk. in rev 4965, If a descriptor is present on a class, or if the name is excluded via the include/ exclude lists, the attribute will not be instrumented via the inherited mapper or via the mapped Table. So your example works with just the @property alone. The r4965 changeset has the side-effect that any previously instrumented attribute will be excluded, too (since ``InstrumentedAttribute`` obviously has the __get__-property). But actually, while I think it's good that any descriptor will be found (not only property-derived ones), this changeset does not solve my particular issue (the property I wanted to exclude was always excluded by ``_should_exclude``). I'll try to put together an example that correctly demonstrates the issue I'm having. \malthe --~--~-~--~~~---~--~~ 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: Overriding table columns with Python-property
Michael Bayer wrote:
well, i can support this in 0.5 trunk. in rev 4965, If a descriptor
is present on a class, or if the name is excluded via the include/
exclude lists, the attribute will not be instrumented via the
inherited mapper or via the mapped Table. So your example works with
just the @property alone.
I've managed to demonstrate the issue in an isolated test (see below).
The only change from the previous is that I've set a default value.
This causes SQLAlchemy to *prefetch* the 'col' column, but this throws
an exception since the column is not mapped.
from sqlalchemy import *
from sqlalchemy.orm import *
e = create_engine('sqlite://')
m = MetaData(e)
t1= Table(
't1', m,
Column('id', Integer, primary_key=True),
Column('col', String(50), default=u),
)
t1.create()
t2= Table(
't2', m,
Column('id', Integer, ForeignKey(t1.id), primary_key=True),
Column('data', String(50)),
)
t2.create()
class T1(object):
pass
class T2(T1):
@property
def col(self):
return uSome read-only value.
polymorphic = (
[T2], t1.join(t2))
mapper(T1, t1)
mapper(
T2, t2,
exclude_properties=('col',),
with_polymorphic=polymorphic,
inherits=T1,
inherit_condition=(t1.c.id==t2.c.id),
)
sess = sessionmaker()()
x = T2()
assert type(T2.col) is property
x.data = some data
sess.save(x)
sess.commit()
sess.clear()
assert sess.query(T2).one().data == some data
assert sess.query(T2).one().col == uSome read-only value.
x = sess.query(T2).one()
x.data = some new data
sess.commit()
assert sess.query(T2).one().data == some new data
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[sqlalchemy] Re: Overriding table columns with Python-property
this issue is not specific to the recent changes; this would happen
even with the old behavior (since exclude_properties was meant to
mean, I dont want SQLA to know about this column at all typically in
a reflection scenario). its fixed in r4966.
On Jul 22, 2008, at 7:27 AM, Malthe Borch wrote:
Michael Bayer wrote:
well, i can support this in 0.5 trunk. in rev 4965, If a descriptor
is present on a class, or if the name is excluded via the include/
exclude lists, the attribute will not be instrumented via the
inherited mapper or via the mapped Table. So your example works with
just the @property alone.
I've managed to demonstrate the issue in an isolated test (see below).
The only change from the previous is that I've set a default value.
This causes SQLAlchemy to *prefetch* the 'col' column, but this throws
an exception since the column is not mapped.
from sqlalchemy import *
from sqlalchemy.orm import *
e = create_engine('sqlite://')
m = MetaData(e)
t1= Table(
't1', m,
Column('id', Integer, primary_key=True),
Column('col', String(50), default=u),
)
t1.create()
t2= Table(
't2', m,
Column('id', Integer, ForeignKey(t1.id), primary_key=True),
Column('data', String(50)),
)
t2.create()
class T1(object):
pass
class T2(T1):
@property
def col(self):
return uSome read-only value.
polymorphic = (
[T2], t1.join(t2))
mapper(T1, t1)
mapper(
T2, t2,
exclude_properties=('col',),
with_polymorphic=polymorphic,
inherits=T1,
inherit_condition=(t1.c.id==t2.c.id),
)
sess = sessionmaker()()
x = T2()
assert type(T2.col) is property
x.data = some data
sess.save(x)
sess.commit()
sess.clear()
assert sess.query(T2).one().data == some data
assert sess.query(T2).one().col == uSome read-only value.
x = sess.query(T2).one()
x.data = some new data
sess.commit()
assert sess.query(T2).one().data == some new data
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[sqlalchemy] Re: Overriding table columns with Python-property
On Jul 19, 2008, at 7:39 AM, Malthe Borch wrote: I tried adapting your example, which admittedly works :-), to a scenario that better resembles mine, but now the property is overriden simply, even when I use ``exclude_properties``. Note that the setup is overly complex, but this should be seen in the light of a larger setup (as you've previously guided me towards, incidentally). OK, this wasn't really the indended usage of exclude_properties, i.e. to block properties from being propagated from a base class where they are present. Right now properties on the base class propagate to subclasses unconditionally - theres no way to override in a subclass.If I decide to rework this today in 0.5, since I had some other issues with the property generation code recently, I'll let you know (it'll either work great with minimal effort, or open up a whole series of issues I don't have time to deal with). So for now you need to move col aside to a different name like _col in the base class and use properties or synonyms to define the behavior of the name col in all cases. --~--~-~--~~~---~--~~ 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: Overriding table columns with Python-property
Michael Bayer wrote: well, i can support this in 0.5 trunk. in rev 4965, If a descriptor is present on a class, or if the name is excluded via the include/ exclude lists, the attribute will not be instrumented via the inherited mapper or via the mapped Table. So your example works with just the @property alone. This is good news indeed. Excellent! \malthe --~--~-~--~~~---~--~~ 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: Overriding table columns with Python-property
On Jul 19, 2008, at 7:39 AM, Malthe Borch wrote: I tried adapting your example, which admittedly works :-), to a scenario that better resembles mine, but now the property is overriden simply, even when I use ``exclude_properties``. Note that the setup is overly complex, but this should be seen in the light of a larger setup (as you've previously guided me towards, incidentally). well, i can support this in 0.5 trunk. in rev 4965, If a descriptor is present on a class, or if the name is excluded via the include/ exclude lists, the attribute will not be instrumented via the inherited mapper or via the mapped Table. So your example works with just the @property alone. --~--~-~--~~~---~--~~ 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: Overriding table columns with Python-property
Michael Bayer wrote:
works for me:
I tried adapting your example, which admittedly works :-), to a scenario
that better resembles mine, but now the property is overriden simply,
even when I use ``exclude_properties``.
Note that the setup is overly complex, but this should be seen in the
light of a larger setup (as you've previously guided me towards,
incidentally).
from sqlalchemy import *
from sqlalchemy.orm import *
e = create_engine('sqlite://')
m = MetaData(e)
t1= Table(
't1', m,
Column('id', Integer, primary_key=True),
Column('col', String(50)),
)
t1.create()
t2= Table(
't2', m,
Column('id', Integer, ForeignKey(t1.id), primary_key=True),
Column('data', String(50)),
)
t2.create()
class T1(object):
pass
class T2(T1):
@property
def col(self):
return uSome read-only value.
polymorphic = (
[T2], t1.join(t2))
mapper(T1, t1)
mapper(
T2, t2,
exclude_properties=('col',),
with_polymorphic=polymorphic,
inherits=T1,
inherit_condition=(t1.c.id==t2.c.id),
)
sess = sessionmaker()()
x = T2()
assert type(T2.col) is property
x.data = some data
sess.save(x)
sess.commit()
sess.clear()
assert sess.query(T2).one().data == some data
assert sess.query(T2).one().col == uSome read-only value.
x = sess.query(T2).one()
x.data = some new data
sess.commit()
assert sess.query(T2).one().data == some new data
\malthe
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[sqlalchemy] Re: Overriding table columns with Python-property
works for me:
from sqlalchemy import *
from sqlalchemy.orm import *
e = create_engine('sqlite://')
m = MetaData(e)
t= Table('t1', m,
Column('id', Integer, primary_key=True),
Column('col', String(50)),
Column('data', String(50)),
)
t.create()
class Mapper(object):
@property
def col(self):
return uSome read-only value.
mapper(Mapper, t, exclude_properties=('col',))
sess = sessionmaker()()
x = Mapper()
x.data = some data
sess.save(x)
sess.commit()
sess.clear()
assert sess.query(Mapper).one().data == some data
assert sess.query(Mapper).one().col == uSome read-only value.
x = sess.query(Mapper).one()
x.data = some new data
sess.commit()
assert sess.query(Mapper).one().data == some new data
On Jul 18, 2008, at 2:24 PM, Malthe Borch wrote:
I have a table 'test' that defines a column 'col'. I map this table
on:
class Mapper(object):
@property
def col(self):
return uSome read-only value.
passing exclude_properties=('col',).
However, when I save and commit an instance of Mapper, I get:
[snip]
UnmappedColumnError: No column test.col is configured on mapper
Mapper...
This is on SQLAlchemy 0.4.6.
\malthe
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