[sqlalchemy] Re: Mapper properties and a callback
i'm not sure how much this would help u, but 0.4 has better support for
your-own-collection-containers. see
http://www.sqlalchemy.org/docs/04/mappers.html#advdatamapping_relation_collections
e.g. subclass some list and u can do the callback at append() or whatever.
Dave Harrison wrote:
Hi all,
I have a situation where I want to declare a relation between two
tables, but I want to be able to run a callback whenever I append to
that relation. Here's an example
class Kennel:
def callback(self, o):
print callback, o
mapper = Mapper(
Kennel,
kennelTable,
properties = {
dogs : relation(
Dog, cascade=all, delete-orphan
),
}
)
So whenever I use mykennel.dogs.append(fred) I want to be able to tell
the relation to call callback() so that I can do some checking on the
object that is being appended.
Is this possible ??
Cheers
Dave
--~--~-~--~~~---~--~~
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 mapped class
Alexandre da Silva wrote: I am already trying go get the list of mapped tables. I currently got a list from sqlalchemy.org.mapper from the weakref mapper_registry, but I don't know if that values are useful for my context. what u need? all tables? see metadata. all mappers? see the mapper_registry the relations inbetween? u have to dig the individual mappers, walk the polymorphisms and inheritances. I also have another question, I have some way to access the mapped class from the table object? probably no, the relation is directional in the other way,. mapper-table; one may have many mappers linked in a way or another to same table. i'm not sure if u can have 2 separate clasess with 2 primary mappers using same table - probably can. and, why u need all this? something like: user_table = Table(...) class User(object) pass mapper(User, user_table) I have some method like user_table.getclass? or another way to get it from orm? thank's for help --~--~-~--~~~---~--~~ 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: Readonly objects/protecting objects from modifications
On Dec 22, 2007, at 12:34 AM, Andreas Jung wrote:
--On 21. Dezember 2007 16:33:34 -0500 Michael Bayer [EMAIL PROTECTED]
wrote:
On Dec 21, 2007, at 3:13 PM, Rick Morrison wrote:
I think the only way something like this should be done is as a test
fixture which decorates classes during unit tests.It would be
fairly clumsy to have in production code.
If you have coworkers who write broken code, the way you solve that
is
by having unit tests which will fail when the coworkers in question
do
something theyre not supposed to. If other people are writing code
that sets attrbutes its not supposed to and breaks things, you need
more tests to catch those conditions. If youre putting code into
production that hasnt been tested, then you need a build process,
automated testing, etc.There is definitely a best practice here
and test driven development is it.
With all respect, this is not a useful answer. Even with tests
(unittests and weeks of manual tests) I had the case that a simple
programming error
(of my own) produced a data disaster after some weeks. There is no
100% test coverage. Tests don't solve all problems. There is
sometimes the need for a better security belt.
I am certainly suggesting a fixture that detects illegal assignments
to attributes. That it be limited to just unit tests is only a
suggestion.To establish this functionality regardless of
environment, like Rick said just create properties which prohibit
assignment. Create mappers like this:
class AttrGetter(object):
def __init__(self, name):
self.name = name
def __get__(self, instance, name):
if instance is None:
return self
return getattr(instance, '_' + name)
def __set__(self, instance, value):
raise AssertionError(Sets are not allowed)
def __delete__(self, instance):
raise AssertionError(Deletes are not allowed)
class MyClass(object):
somecolumn = AttrGetter('somecolumn')
someothercolumn = AttrGetter('someothercolumn')
mapper(MyClass, sometable, properties={
'_somecolumn':sometable.c.somecolumn,
'_someothercolumn':sometable.c.someothercolumn
})
To automate the above process with no modifications to source code,
create an instrumented mapper() function which applies the above
recipe to all table columns:
from sqlalchemy.orm import mapper as _mapper
def mapper(cls, table, **kwargs):
attrs = {}
for c in table.c:
attrs['_' + c.key] = c
setattr(cls, c.key, AttrGetter(c.key))
properties = kwargs.setdefault('properties', {})
properties.update(attrs)
return _mapper(cls, table, **kwargs)
Hope this helps.
--~--~-~--~~~---~--~~
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] Changing the type/class of an object using polymorphic tables in ORM
I don't know if I'm too clear, but I'll try to explain it. I'm using a set up similar to the one in http://www.sqlalchemy.org/docs/04/mappers.html#advdatamapping_mapper_inheritance_joined . I want to be able to change the type of an object. For example, in the example in the link above, I want to be able to change an Employee into an Engineer and viceversa. Is there a way to do this? Or should I delete the object and create a new one? And in the last case (create new), how would I be able to update ForeignKey relationships referencing the changed object? Thanks in advance for your help. --~--~-~--~~~---~--~~ 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: Caching
merge is working rudimentally for objects with unloaded scalar/ instance/collection attributes in r3974. whats not yet happening is the merging of the various query.options() that may be present on the original deferred loader, which means the merged instance wont necessarily maintain the exact eager/lazy/deferred loading of the original, but this is not especially critical for the basic idea to work. example script using merge attached. Michael, thanks a lot for your support! --~--~-~--~~~---~--~~ 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 mapped class
what u need? I need the list of mapped Classes, if mapper_registry have all classes I can use it. all tables? see metadata. all mappers? see the mapper_registry the relations inbetween? u have to dig the individual mappers, walk the polymorphisms and inheritances. I just want a list containing the relation class-table and table-class, but I think it's not available, so I will create my own. probably no, the relation is directional in the other way,. mapper-table; one may have many mappers linked in a way or another to same table. i'm not sure if u can have 2 separate clasess with 2 primary mappers using same table - probably can. Creating my own mapping list I will get what I need for now. and, why u need all this? At my development scenario I want to create a Form on application just defining some properties at Mapped Class, and just what I need is a list with the links table-class, to get one or other depends where am I, other thing I need/want is create some database additional objects (triggers, procedures, etc) just creating a staticmethod at mapped class, i.e get_addit_metadata() that's all for now I will implement my own mapper function, and it will inside add the class-table to a list to keep tracking and inside call the sqlalchemy mapper method. Thank's for all replies Best Regards, Alexandre --~--~-~--~~~---~--~~ 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: Changing the type/class of an object using polymorphic tables in ORM
On Dec 22, 2007, at 3:27 PM, andresj wrote: I don't know if I'm too clear, but I'll try to explain it. I'm using a set up similar to the one in http://www.sqlalchemy.org/docs/04/mappers.html#advdatamapping_mapper_inheritance_joined . I want to be able to change the type of an object. For example, in the example in the link above, I want to be able to change an Employee into an Engineer and viceversa. Is there a way to do this? Or should I delete the object and create a new one? And in the last case (create new), how would I be able to update ForeignKey relationships referencing the changed object? we dont support this feature right now, its something we will implement eventually but its fairly complicated since we have to detect the condition, figure out additional tables which require INSERTs or DELETEs depending on the class change, etc. So for now, your best bet is to issue the SQL directly to the database for the particular class change you want to do, remove the objects in question from the session using expunge(), and reload as the new class. This would involve, for motion from a superclass to subclass INSERTing into the desired joined table, for motion from subclass to superclass DELETEing from the joined table, or for motion from one subclass to another INSERTing and DELETEing. For deeper inheritance, the above pattern becomes more complex. But I dont think delete and create new is necessary here - the base table can remain unchanged except for issuing an UPDATE to the discriminator column, assuming you have one. --~--~-~--~~~---~--~~ 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: Changing the type/class of an object using polymorphic tables in ORM
Thanks, I will use the approach you describe here when I get to that point in the development proccess :). So for now, your best bet is to issue the SQL directly to the database for the particular class change you want to do, remove the objects in question from the session using expunge(), and reload as the new class. Could you elaborate a bit on using expunge(), please? And when you say issuing SQL directly to the database you mean using the non-orm part of sqlalchemy, right? This would involve, for motion from a superclass to subclass INSERTing into the desired joined table, for motion from subclass to superclass DELETEing from the joined table, or for motion from one subclass to another INSERTing and DELETEing. I get what you are saying, just tha tI think that from a superclass to subclass would involve a DELETE, right? And viceversa, an INSERT... Unless we are using different terms for superclass and subclass in which case I apologize :) For deeper inheritance, the above pattern becomes more complex. But I dont think delete and create new is necessary here - the base table can remain unchanged except for issuing an UPDATE to the discriminator column, assuming you have one. I'm happy to know that I don't have to delete and create a new one, because it would be tedious to update the references... Thanks for your help -- Andres --~--~-~--~~~---~--~~ 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: Making it possible to use custom properties in query.filter expressions.
On Dec 22, 5:07 pm, Michael Bayer [EMAIL PROTECTED] wrote:
a synonym() is used so that your attributes are properly available in
filter(). This functionality has been vastly improved in the current
SVN trunk which resolves all the issues you outline above, and will be
available in release 0.4.2. If you checkout the SVN trunk, you can do:
class MyAddress(object):
def _set_email(self, email):
self._email = email
def _get_email(self):
return self._email
email = property(_get_email, _set_email)
mapper(MyAddress, addresses_table, properties = {
'email':synonym('_email', map_column=True)
})
which automatically maps the column to the _email attribute, and
also instruments the email property with the SQL comparator methods.
Thank's for the info, but is SVN ready for production use (kinda like
Django's SVN, which is recommended by Django)? I mean, can I use it
for my real-world projects without fearing that in any moment it will
not work? And in any case, do you know when is 0.4.2 scheduled to
come?
--
Andres
--~--~-~--~~~---~--~~
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
-~--~~~~--~~--~--~---
