Versioning and multi-level inheritance

[JPLaverdure]

Hello,

I'm trying to use the versioning recipe describe on the website along
with a multi-level inheritance model (Joined-Table inheritance)

Here are my declarative statements:

[code]
class Sample(Base):
__metaclass__ = VersionedMeta
__tablename__ = 'sample'
__table_args__ = {'schema': 'test'}

id = Column(Integer, primary_key=True)
discriminator = Column('type', String(50))
token = Column(String(128), nullable=False)
source_sample_id = Column(Integer, ForeignKey('test.sample.id'))

children = relationship("Sample", backref=backref('source_sample',
remote_side=id), single_parent=True)

__mapper_args__ = {'polymorphic_on': discriminator,
'polymorphic_identity':'sample'}

def __init__(self, token, source_sample_id=None):
self.token = token
self.source_sample_id = source_sample_id

class Tissue(Sample):
__metaclass__ = VersionedMeta
__tablename__ = 'tissue'
__mapper_args__ = {'polymorphic_identity': 'tissue'}
__table_args__ = {'schema': 'test'}

id = Column(Integer, ForeignKey('test.sample.id'),
primary_key=True)
concentration = Column(String(32))

def __init__(self, token, concentration, source_sample_id=None):
super(Sample, self).__init__(token, source_sample_id)
self.concentration = concentration

class LeukemicTissue(Tissue):
__metaclass__ = VersionedMeta
__tablename__ = 'leukemic_tissue'
__mapper_args__ = {'polymorphic_identity': 'leukemic_tissue'}
__table_args__ = {'schema': 'test'}

id = Column(Integer, ForeignKey('test.tissue.id'),
primary_key=True)
leukemia = Column(String)

def __init__(self, token, concentration, leukemia,
source_sample_id=None):
super(Tissue, self).__init__(token, concentration,
source_sample_id)
self.leukemia = leukemia
[/code]


Whenever I try to "create_all()" I get the following error:
sqlalchemy.exc.ArgumentError: Can't find any foreign key relationships
between 'tissue_history' and 'leucegene_tissue_history'.

Single level-inheritance works beautifully (ie if I stop at "Tissue"
and don't declare the "LeukemicTissue") but I really need a multi-
level inheritance scheme to work..

Can anyone give me any pointers ?

Thanks !!

[Michael Bayer]

apply this patch to history_meta.py

diff -r 7c65c0cdd3c8 examples/versioning/history_meta.py
--- a/examples/versioning/history_meta.py Tue Jun 14 19:57:21 2011 -0400
+++ b/examples/versioning/history_meta.py Thu Jun 16 12:04:43 2011 -0400
@@ -35,7 +35,7 @@
col.unique = False

if super_mapper and col_references_table(column, super_mapper.local_table):
- super_fks.append((col.key, list(super_history_mapper.base_mapper.local_table.primary_key)[0]))
+ super_fks.append((col.key, list(super_history_mapper.local_table.primary_key)[0]))

cols.append(col)

as you can see, the foreign key generation is pulling from the "base" mapper which isn't the case in a multilevel situation, it needs to pull the FKs from the immediate super-mapper.

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[JPLaverdure]

Fantastic ! And so quick to answer !

Thank you very much for your help, works like a charm now.
Has this patch been applied in the 0.7 release of sqlalchemy ? (I was
working with 0.6.7)

JP

[gary clark]

Hello,

I am trying to connect to another machine to access the mysql database. I have a firewall on one machine which restricts alot of the accesses from outside.

I am doing something like:

create_engine('mysql://root:p...@192.168.1.10/database',poolClass=NullPool)

Could someone be so kind and tell me what needs to be open on the other machine to connect and what the default port is?

Thanks,
Gary C

[Michael Bayer]

i committed it to 0.7.

technically the logic there should search up the chain of mappers for an FK in a parent table, its still making a bit of an assumption.

[JPLaverdure]

I just realised the following issue:

When I create the following relationship:

class Container(Base):

    __metaclass__ = VersionedMeta

    __tablename__ = 'container'

    __table_args__ = {'schema':'storage'}

    id = Column(Integer, primary_key=True)

    discriminator = Column('type', String(64))

    token = Column(String(128), nullable=False)

    description = Column(String)

    

    __mapper_args__ = {'polymorphic_on': discriminator, 'polymorphic_identity':'container'}

class Box(Container):

    __metaclass__ = VersionedMeta

    __tablename__ = 'box'

    __table_args__ = {'schema':'storage'}

    __mapper_args__ = {'polymorphic_identity': 'box'}

    

    id = Column(Integer, ForeignKey('storage.container.id', onupdate="cascade", ondelete="cascade"), primary_key=True)

    barcode = Column(String(64))

Even though box_history gets created, no "version" column is added to the box table and any modification to a Box entity does not log the change in the _history table.

Could anyone please point out what I'm doing wrong ?

I tried removing the metaclass declaration from the Box entity since it would basically inherit it from Container but that didn't help in solving my issue.

Thank you !!

[Michael Bayer]

"version" is only on your Container table since it will always have a row corresponding to each Box row, so "box.version" is not necessary.  You can change this by changing:

    if not super_history_mapper:

        cls.version = Column('version', Integer, default=1, nullable=False)

to:

        cls.version = Column('version', Integer, default=1, nullable=False)

then ensuring that Box.version is also written on update.

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[JPLaverdure]

Hi Michael,

Thank you for your reply.

Unfortunately, the mistake was all mine... 

At some point (and for an obscure reason...), I had stopped using the VersionedListener so changes were no longer registering in the DB :-/

So sorry !

JP

[Jean-Philippe Laverdure]

JP

--
Je-Pe