Re: [sqlalchemy] Re: Elixir question
On 02/03/2012 12:08 PM, lars van gemerden wrote:
I should probably make the pair method:
def pair(name1, name2):
p1, p2 = Pairs(name1), Pairs(name2)
p1.other = p2
p2.other = p1
On Feb 3, 11:57 am, lars van gemerdenl...@rational-it.com wrote:
Hi, I am trying to sote pairs in a table as follows:
#--
from elixir import *
metadata.bind = sqlite:///:memory:
metadata.bind.echo = False
class Pairs(Entity):
name = Field(String(50), primary_key = True)
other = OneToOne('Pairs', inverse = 'other')
You can't have a OneToOne as inverse for a OneToOne, even less for
itself. Valid relationship pairs are:
ManyToOne - OneToOne
ManyToOne - OneToMany
ManyToMany - ManyToMany
In your case you want:
class Pairs(Entity):
name = Field(String(50), primary_key = True)
other1 = ManyToOne('Pairs', inverse = 'other2')
other2 = OneToOne('Pairs', inverse = 'other1')
and if your database really only stores pairs, a property might make it
more elegant:
@property
def other(self):
return self.other1 if self.other1 is not None else self.other2
As a side note, you probably do not want to use Elixir for a new
project, as Elixir is not maintained anymore.
-G.
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[sqlalchemy] Re: Elixir question
OK, thank you,
I went back to SQLA and came up with this for now (simplified):
class Pairs(Base):
__tablename__ = 'Pairs'
name = Column(String(20), primary_key=True)
other_name = Column(String(20), ForeignKey('Pairs.name'), nullable
= False)
other = relationship('Pairs',
primaryjoin = 'Pairs.name ==
Pairs.other_name',
remote_side=[name])
def __init__(self, name):
self.name = name
def __repr__(self):
return (%s, %s) % (self.name, self.other.name)
def pair(name1, name2):
p1, p2 = Pairs(name1), Pairs(name2)
p1.other_name = name2
p2.other_name = name1
return p1, p2
if __name__ == '__main__':
p1, p2 = pair('apple', 'pear')
session.add_all([p1, p2])
session.commit()
for p in session.query(Pairs).all():
print p
assert p1.other.other is p1
--
Note that there is no backref on other and that the primaryjoin is
completely written out (otherwise a got a mysterious (to me) error,
when using joined inheritance at the same time).
This solution is key to my datamodel. Does anyone see any drawbacks?
Cheers, Lars
On Feb 5, 10:50 am, Gaëtan de Menten gdemen...@gmail.com wrote:
On 02/03/2012 12:08 PM, lars van gemerden wrote:
I should probably make the pair method:
def pair(name1, name2):
p1, p2 = Pairs(name1), Pairs(name2)
p1.other = p2
p2.other = p1
On Feb 3, 11:57 am, lars van gemerdenl...@rational-it.com wrote:
Hi, I am trying to sote pairs in a table as follows:
#--
from elixir import *
metadata.bind = sqlite:///:memory:
metadata.bind.echo = False
class Pairs(Entity):
name = Field(String(50), primary_key = True)
other = OneToOne('Pairs', inverse = 'other')
You can't have a OneToOne as inverse for a OneToOne, even less for
itself. Valid relationship pairs are:
ManyToOne - OneToOne
ManyToOne - OneToMany
ManyToMany - ManyToMany
In your case you want:
class Pairs(Entity):
name = Field(String(50), primary_key = True)
other1 = ManyToOne('Pairs', inverse = 'other2')
other2 = OneToOne('Pairs', inverse = 'other1')
and if your database really only stores pairs, a property might make it
more elegant:
@property
def other(self):
return self.other1 if self.other1 is not None else self.other2
As a side note, you probably do not want to use Elixir for a new
project, as Elixir is not maintained anymore.
-G.
--
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[sqlalchemy] Re: Elixir question
Sorry, scrap the remark about primaryjoin ... inheritance. INheritance
wasn't the problem.
On Feb 5, 1:27 pm, lars van gemerden l...@rational-it.com wrote:
OK, thank you,
I went back to SQLA and came up with this for now (simplified):
class Pairs(Base):
__tablename__ = 'Pairs'
name = Column(String(20), primary_key=True)
other_name = Column(String(20), ForeignKey('Pairs.name'), nullable
= False)
other = relationship('Pairs',
primaryjoin = 'Pairs.name ==
Pairs.other_name',
remote_side=[name])
def __init__(self, name):
self.name = name
def __repr__(self):
return (%s, %s) % (self.name, self.other.name)
def pair(name1, name2):
p1, p2 = Pairs(name1), Pairs(name2)
p1.other_name = name2
p2.other_name = name1
return p1, p2
if __name__ == '__main__':
p1, p2 = pair('apple', 'pear')
session.add_all([p1, p2])
session.commit()
for p in session.query(Pairs).all():
print p
assert p1.other.other is p1
--
Note that there is no backref on other and that the primaryjoin is
completely written out (otherwise a got a mysterious (to me) error,
when using joined inheritance at the same time).
This solution is key to my datamodel. Does anyone see any drawbacks?
Cheers, Lars
On Feb 5, 10:50 am, Gaëtan de Menten gdemen...@gmail.com wrote:
On 02/03/2012 12:08 PM, lars van gemerden wrote:
I should probably make the pair method:
def pair(name1, name2):
p1, p2 = Pairs(name1), Pairs(name2)
p1.other = p2
p2.other = p1
On Feb 3, 11:57 am, lars van gemerdenl...@rational-it.com wrote:
Hi, I am trying to sote pairs in a table as follows:
#--
from elixir import *
metadata.bind = sqlite:///:memory:
metadata.bind.echo = False
class Pairs(Entity):
name = Field(String(50), primary_key = True)
other = OneToOne('Pairs', inverse = 'other')
You can't have a OneToOne as inverse for a OneToOne, even less for
itself. Valid relationship pairs are:
ManyToOne - OneToOne
ManyToOne - OneToMany
ManyToMany - ManyToMany
In your case you want:
class Pairs(Entity):
name = Field(String(50), primary_key = True)
other1 = ManyToOne('Pairs', inverse = 'other2')
other2 = OneToOne('Pairs', inverse = 'other1')
and if your database really only stores pairs, a property might make it
more elegant:
@property
def other(self):
return self.other1 if self.other1 is not None else self.other2
As a side note, you probably do not want to use Elixir for a new
project, as Elixir is not maintained anymore.
-G.
--
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For more options, visit this group at
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[sqlalchemy] Re: Elixir question
I should probably make the pair method:
def pair(name1, name2):
p1, p2 = Pairs(name1), Pairs(name2)
p1.other = p2
p2.other = p1
On Feb 3, 11:57 am, lars van gemerden l...@rational-it.com wrote:
Hi, I am trying to sote pairs in a table as follows:
#--
from elixir import *
metadata.bind = sqlite:///:memory:
metadata.bind.echo = False
class Pairs(Entity):
name = Field(String(50), primary_key = True)
other = OneToOne('Pairs', inverse = 'other')
def __init__(self, name):
self.name = name
def pair(name1, name2):
p1, p2 = Pairs(name1), Pairs(name2)
p1.other = p2
if __name__ == '__main__':
setup_all()
create_all()
pair('p1', 'p2')
#--
I am not very famiiar with SQL etc. but logically this seems possible
(please orrect me if I am wrong). However I get the following error:
File D:\Documents\Code\Eclipse\workspace\SQLAdata\src\tests.py, line
22, in module
setup_all()
File build\bdist.win-amd64\egg\elixir\__init__.py, line 94, in
setup_all
File build\bdist.win-amd64\egg\elixir\entity.py, line 951, in
setup_entities
File build\bdist.win-amd64\egg\elixir\entity.py, line 198, in
create_pk_cols
File build\bdist.win-amd64\egg\elixir\entity.py, line 481, in
call_builders
File build\bdist.win-amd64\egg\elixir\relationships.py, line 448,
in create_pk_cols
File build\bdist.win-amd64\egg\elixir\relationships.py, line 791,
in create_keys
File build\bdist.win-amd64\egg\elixir\relationships.py, line 521,
in inverse
AssertionError: Relationships 'other' in entity 'Pair' and 'other' in
entity 'Pair' cannot be inverse of each other because their types do
not form a valid combination.
Can anyone help me to understand the error and possibly fix it?
Thanks in advance, Lars
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