if you assign a mapper to Base and a separate mapper to Person youre
going to have problems, since each class is associated with a mapper
via an attribute "_mapper" attached to the class, and you effectively
have two different mappers dealing with Person objects and its going
to get ugly. you might want to try insuring that the "_mapper"
attribute attached to Person is the same as that attached to Base.
I still think separate mappers and using the method described in
"Result Set Mapping" might be less error prone. but try seeing how
well you do if you maintain control of the "_mapper" attribute (its
also described in http://www.sqlalchemy.org/docs/
adv_datamapping.myt#adv_datamapping_class ).
On Feb 28, 2006, at 3:02 PM, Marko Mikulicic wrote:
On 28.02.2006., at 20:10, Michael Bayer wrote:
Ah nice.
When I select objects from Person.select() I get the same
instance. Is possible to obtain this behaviour using custom
object creation?
show me more specifically what you mean.
from the previous attachments (augmented with prints):
print "---------------"
print "Using pm mapper"
print "---------------"
print pm.select()
for o in pm.select():
o.doSomething()
print pm.select()
# commit necessary to see changes because modifications are not
tracked with the "pm" mapper
print "committing"
objectstore.commit()
print pm.select()
print "-------------------"
print "Using Person.mapper"
print "-------------------"
# Works without commit because the mapper returns the same instances
for o in Person.select():
o.doSomething()
print Person.select()
**************
outputs:
**************
[]
---------------
Using pm mapper
---------------
[<Organization 18388048: Label Bleu, David Krakauer>, <Person
18389968: Smith, John>, <Base: 18362224: base>]
organization adding x to contact
person adding y to address
base doing nothing
[<Organization 18362192: Label Bleu, David Krakauer>, <Person
18390608: Smith, John>, <Base: 18362224: base>]
committing
[<Organization 18389392: Label Bleu, David Krakauerx>, <Person
18389008: Smith, Johny>, <Base: 18362224: base>]
-------------------
Using Person.mapper
-------------------
person adding y to address
[<Person 18389008: Smith, Johnyy>]
-----------
in the first example every select from the pm mapper yeilds
different objects (different python id()).
In this case the modifications are not visible until the commit.
in the second example the modification of the objects are directly
visible in the same thread because Person.select() returns the same
objects.
I was wondering if it was possible to have the same behaviour using
MapperExtension create_instance.
--
marko
-------------------------------------------------------
This SF.Net email is sponsored by xPML, a groundbreaking scripting
language
that extends applications into web and mobile media. Attend the
live webcast
and join the prime developer group breaking into this new coding
territory!
http://sel.as-us.falkag.net/sel?
cmd=lnk&kid=110944&bid=241720&dat=121642
_______________________________________________
Sqlalchemy-users mailing list
Sqlalchemy-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/sqlalchemy-users
-------------------------------------------------------
This SF.Net email is sponsored by xPML, a groundbreaking scripting language
that extends applications into web and mobile media. Attend the live webcast
and join the prime developer group breaking into this new coding territory!
http://sel.as-us.falkag.net/sel?cmd=lnk&kid=110944&bid=241720&dat=121642
_______________________________________________
Sqlalchemy-users mailing list
Sqlalchemy-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/sqlalchemy-users
