[sqlalchemy] Accessing several databases
Hello, I'm intending to use sqalchemy with orm for loading and storing my application's project files. Each sqlite database would be a project file, that will have several tables. I'd like to work with projects like this: project1=AppProject(/tmp/pr1.sqlite); project2=AppProject(/tmp/pr2.sqlite); item1 = project1.getItem(5) # item1 should be and object of a mapped class. item1.value=test anotheritem = project1.getNewItem() anotheritem.value=this is new # this should flush and commit the underlying session for project1, #modifying item with id 5, and adding a new one project1.commitEverything() item2 = project2.getItem(8) item2.value = another test project2.commitEverything() The problem i'm facing is how to create the engine, metadata, mapper, session, and the orm classes for each AppProject instance. I'm not sure if this is supported or even a good idea. Thanks, Julian J. M. -- 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 sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
RE: [sqlalchemy] Accessing several databases
-Original Message-
From: sqlalchemy@googlegroups.com [mailto:sqlalchemy@googlegroups.com]
On Behalf Of Julian J. M.
Sent: 16 June 2011 11:43
To: sqlalchemy
Subject: [sqlalchemy] Accessing several databases
Hello,
I'm intending to use sqalchemy with orm for loading and storing my
application's project files. Each sqlite database would be a project
file, that will have several tables.
I'd like to work with projects like this:
project1=AppProject(/tmp/pr1.sqlite);
project2=AppProject(/tmp/pr2.sqlite);
item1 = project1.getItem(5) # item1 should be and object of a mapped
class.
item1.value=test
anotheritem = project1.getNewItem()
anotheritem.value=this is new
# this should flush and commit the underlying session for project1,
#modifying item with id 5, and adding a new one
project1.commitEverything()
item2 = project2.getItem(8)
item2.value = another test
project2.commitEverything()
The problem i'm facing is how to create the engine, metadata, mapper,
session, and the orm classes for each AppProject instance.
I'm not sure if this is supported or even a good idea.
Thanks,
Julian J. M.
I think this should be pretty easy with a separate SQLAlchemy Session
per project. You would define all your mappers and so on without any
reference to a specific database:
##
# your_db_module.py
import sqlalchemy as sa
import sqlalchemy.orm as saorm
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()
class ProjectItem(Base):
__tablename__ = 'project_item'
id = sa.Column(sa.Integer, autoincrement=True, primary_key=True)
# other columns etc.
Then your AppProject class would look something like this:
##
# appproject.py
import sqlalchemy as sa
import sqlalchemy.orm as saorm
from your_db_module import ProjectItem
class AppProject(object):
def __init__(self, filename):
self.engine = sa.create_engine('sqlite://' + filename)
self.session = saorm.Session(bind=self.engine)
def get_item(self, id):
return self.session.query(ProjectItem).get(id)
Hope that helps,
Simon
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RE: [sqlalchemy] mapping a class linked with two other classes (AttributeError: 'str' object has no attribute '_sa_instance_state')
-Original Message-
From: sqlalchemy@googlegroups.com [mailto:sqlalchemy@googlegroups.com]
On Behalf Of Jules Stevenson
Sent: 16 June 2011 08:44
To: sqlalchemy@googlegroups.com
Subject: [sqlalchemy] mapping a class linked with two other classes
(AttributeError: 'str' object has no attribute '_sa_instance_state')
Hi List,
I have a user class, a contact class, and a googleID class.
the contact class has can have a googleID per user in the system. I'm
trying to map it out as follows:
# ArkContact - clientprojectshot module
orm.mapper(ArkContact, contacts_table, properties={
'notes': orm.relation(ArkNote,
secondary=contact_notes_table,
backref='contacts',
single_parent=True,
cascade=all, delete, delete-orphan),
'users': orm.relation(ArkUser,
secondary=user_contact_table,
backref='contacts'),
'google_UID': orm.relation(ArkUserContactGUID,
cascade=all, delete,
backref='user')
})
#user contact google_GUID
user_contact_UID = sa.Table('user_contact_UID_table', meta.metadata,
sa.Column('user_id', sa.types.Integer, sa.ForeignKey('users.id'),
primary_key=True),
sa.Column('contact_id', sa.types.Integer,
sa.ForeignKey('contacts.id'), primary_key=True),
sa.Column('google_UID', sa.types.String(length = 1024))
)
class ArkUserContactGUID(object):
def __init__(self):
pass
orm.mapper(ArkUserContactGUID, user_contact_UID)
This raises two issues, the first is that an instrumented list is
returned for the google_UID paramter on the contact object, whereas
there should only ever be one (since as an operator there is only
ever
one user signed in - you).
For one-to-one relationships, you should supply uselist=False to your
relationship:
http://www.sqlalchemy.org/docs/orm/relationships.html#one-to-one
The second is it outright errors :), presumably because my mapping is
off:
File 'C:\\ark\\ark\\controllers\\contacts.py', line 368 in
initial_sync
contact_sync.initial_sync()
File 'C:\\ark\\ark\\arkTools\\arkGoogle.py', line 121 in initial_sync
self.add_contact_to_google(contact)
File 'C:\\ark\\ark\\arkTools\\arkGoogle.py', line 259 in
add_contact_to_google
data.google_UID.append(entry.get_id())
File 'C:\\ark\\env_x64\\lib\\site-packages\\sqlalchemy-0.7.1-
py2.6.egg\\sqlalchemy\\orm\\collections.py',
line 952 in append
item = __set(self, item, _sa_initiator)
File 'C:\\ark\\env_x64\\lib\\site-packages\\sqlalchemy-0.7.1-
py2.6.egg\\sqlalchemy\\orm\\collections.py',
line 927 in __set
item = getattr(executor, 'fire_append_event')(item, _sa_initiator)
File 'C:\\ark\\env_x64\\lib\\site-packages\\sqlalchemy-0.7.1-
py2.6.egg\\sqlalchemy\\orm\\collections.py',
line 618 in fire_append_event
item, initiator)
File 'C:\\ark\\env_x64\\lib\\site-packages\\sqlalchemy-0.7.1-
py2.6.egg\\sqlalchemy\\orm\\attributes.py',
line 741 in fire_append_event
value = fn(state, value, initiator or self)
File 'C:\\ark\\env_x64\\lib\\site-packages\\sqlalchemy-0.7.1-
py2.6.egg\\sqlalchemy\\orm\\unitofwork.py',
line 35 in append
item_state = attributes.instance_state(item)
AttributeError: 'str' object has no attribute '_sa_instance_state'
Many thanks for any help!
Jules
You're passing a string (presumably the result of entry.get_id()) where
SA is expecting an instance of a mapped class. I haven't looked at your
mapping in detail, but rather than this:
data.google_UID.append(entry.get_id())
you probably want something like this:
obj = ArkUserContactGUID(google_UID=entry.get_id())
data.google_UID.append(obj)
(If I've misunderstood your mapping, these class names are probably
wrong)
Hope that helps,
Simon
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Re: [sqlalchemy] Accessing several databases
Thank you very much. I'll try that.
I was confused by this howto:
http://turbogears.org/2.1/docs/main/MultipleDatabases.html
They call declarative_base() for each each database... I thought I
needed that for each AppProject instance...
Anyway, thanks agaon for the example. I'll let you know.
Julian.
On Thu, Jun 16, 2011 at 13:54, King Simon-NFHD78
simon.k...@motorolasolutions.com wrote:
-Original Message-
From: sqlalchemy@googlegroups.com [mailto:sqlalchemy@googlegroups.com]
On Behalf Of Julian J. M.
Sent: 16 June 2011 11:43
To: sqlalchemy
Subject: [sqlalchemy] Accessing several databases
Hello,
I'm intending to use sqalchemy with orm for loading and storing my
application's project files. Each sqlite database would be a project
file, that will have several tables.
I'd like to work with projects like this:
project1=AppProject(/tmp/pr1.sqlite);
project2=AppProject(/tmp/pr2.sqlite);
item1 = project1.getItem(5) # item1 should be and object of a mapped
class.
item1.value=test
anotheritem = project1.getNewItem()
anotheritem.value=this is new
# this should flush and commit the underlying session for project1,
#modifying item with id 5, and adding a new one
project1.commitEverything()
item2 = project2.getItem(8)
item2.value = another test
project2.commitEverything()
The problem i'm facing is how to create the engine, metadata, mapper,
session, and the orm classes for each AppProject instance.
I'm not sure if this is supported or even a good idea.
Thanks,
Julian J. M.
I think this should be pretty easy with a separate SQLAlchemy Session
per project. You would define all your mappers and so on without any
reference to a specific database:
##
# your_db_module.py
import sqlalchemy as sa
import sqlalchemy.orm as saorm
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()
class ProjectItem(Base):
__tablename__ = 'project_item'
id = sa.Column(sa.Integer, autoincrement=True, primary_key=True)
# other columns etc.
Then your AppProject class would look something like this:
##
# appproject.py
import sqlalchemy as sa
import sqlalchemy.orm as saorm
from your_db_module import ProjectItem
class AppProject(object):
def __init__(self, filename):
self.engine = sa.create_engine('sqlite://' + filename)
self.session = saorm.Session(bind=self.engine)
def get_item(self, id):
return self.session.query(ProjectItem).get(id)
Hope that helps,
Simon
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Re: [sqlalchemy] mapping a class linked with two other classes (AttributeError: 'str' object has no attribute '_sa_instance_state')
Hi Simon, thank you very much for your help (again!), and yes, that's
how I'm using the mapping :).
I'm now getting an SQL error, I think because the user is not being
pulled automatically through when trying to add the
ArkUserContactGUID:
OperationalError: (OperationalError) (1364, Field 'user_id' doesn't
have a default value) 'INSERT INTO `user_contact_UID_table`
(contact_id, uid) VALUES (%s, %s)' (2L,
'http://www.google.com/m8/feeds/contacts/jules%40kettlestudio.co.uk/base/7c5456c108b2111b')
File 'C:\\ark\\ark\\controllers\\contacts.py', line 368 in initial_sync
contact_sync.initial_sync()
File 'C:\\ark\\ark\\arkTools\\arkGoogle.py', line 121 in initial_sync
self.add_contact_to_google(contact)
File 'C:\\ark\\ark\\arkTools\\arkGoogle.py', line 263 in add_contact_to_google
meta.Session.commit()
File
'C:\\ark\\env_x64\\lib\\site-packages\\sqlalchemy-0.7.1-py2.6.egg\\sqlalchemy\\orm\\scoping.py',
line 113 in do
return getattr(self.registry(), name)(*args, **kwargs)
File
'C:\\ark\\env_x64\\lib\\site-packages\\sqlalchemy-0.7.1-py2.6.egg\\sqlalchemy\\orm\\session.py',
line 617 in commit
self.transaction.commit()
File
'C:\\ark\\env_x64\\lib\\site-packages\\sqlalchemy-0.7.1-py2.6.egg\\sqlalchemy\\orm\\session.py',
line 293 in commit
self._prepare_impl()
File
'C:\\ark\\env_x64\\lib\\site-packages\\sqlalchemy-0.7.1-py2.6.egg\\sqlalchemy\\orm\\session.py',
line 277 in _prepare_impl
self.session.flush()
File
'C:\\ark\\env_x64\\lib\\site-packages\\sqlalchemy-0.7.1-py2.6.egg\\sqlalchemy\\orm\\session.py',
line 1473 in flush
self._flush(objects)
File
'C:\\ark\\env_x64\\lib\\site-packages\\sqlalchemy-0.7.1-py2.6.egg\\sqlalchemy\\orm\\session.py',
line 1542 in _flush
flush_context.execute()
File
'C:\\ark\\env_x64\\lib\\site-packages\\sqlalchemy-0.7.1-py2.6.egg\\sqlalchemy\\orm\\unitofwork.py',
line 327 in execute
rec.execute(self)
File
'C:\\ark\\env_x64\\lib\\site-packages\\sqlalchemy-0.7.1-py2.6.egg\\sqlalchemy\\orm\\unitofwork.py',
line 471 in execute
uow
File
'C:\\ark\\env_x64\\lib\\site-packages\\sqlalchemy-0.7.1-py2.6.egg\\sqlalchemy\\orm\\mapper.py',
line 2163 in _save_obj
execute(statement, params)
File
'C:\\ark\\env_x64\\lib\\site-packages\\sqlalchemy-0.7.1-py2.6.egg\\sqlalchemy\\engine\\base.py',
line 1358 in execute
params)
File
'C:\\ark\\env_x64\\lib\\site-packages\\sqlalchemy-0.7.1-py2.6.egg\\sqlalchemy\\engine\\base.py',
line 1491 in _execute_clauseelement
compiled_sql, distilled_params
File
'C:\\ark\\env_x64\\lib\\site-packages\\sqlalchemy-0.7.1-py2.6.egg\\sqlalchemy\\engine\\base.py',
line 1599 in _execute_context
context)
File
'C:\\ark\\env_x64\\lib\\site-packages\\sqlalchemy-0.7.1-py2.6.egg\\sqlalchemy\\engine\\base.py',
line 1592 in _execute_context
context)
File
'C:\\ark\\env_x64\\lib\\site-packages\\sqlalchemy-0.7.1-py2.6.egg\\sqlalchemy\\engine\\default.py',
line 325 in do_execute
cursor.execute(statement, parameters)
File 'C:\\ark\\env_x64\\lib\\site-packages\\MySQLdb\\cursors.py', line
173 in execute
self.errorhandler(self, exc, value)
File 'C:\\ark\\env_x64\\lib\\site-packages\\MySQLdb\\connections.py',
line 36 in defaulterrorhandler
raise errorclass, errorvalue
OperationalError: (OperationalError) (1364, Field 'user_id' doesn't
have a default value) 'INSERT INTO `user_contact_UID_table`
(contact_id, uid) VALUES (%s, %s)' (2L,
'http://www.google.com/m8/feeds/contacts/jules%40kettlestudio.co.uk/base/7c5456c108b2111b')
I think this is because the contacts object uses a many to many
relationship (a contact can belong to any or all users), code as
follows:
# ArkContact - clientprojectshot module
orm.mapper(ArkContact, contacts_table, properties={
'notes': orm.relation(ArkNote,
secondary=contact_notes_table,
backref='contacts',
single_parent=True,
cascade=all, delete, delete-orphan),
'users': orm.relation(ArkUser,
secondary=user_contact_table,
backref='contacts'),
'google_UID': orm.relation(ArkUserContactGUID,
cascade=all, delete,
uselist=False,
backref='user')
})
I'm thinking I should join between the user and ArkUserContactGUID
somehow, but don't know how...
Many thanks,
Jules
On Thu, Jun 16, 2011 at 2:04 PM, King Simon-NFHD78
simon.k...@motorolasolutions.com wrote:
-Original Message-
From: sqlalchemy@googlegroups.com [mailto:sqlalchemy@googlegroups.com]
On Behalf Of Jules Stevenson
Sent: 16 June 2011 08:44
To: sqlalchemy@googlegroups.com
Subject: [sqlalchemy] mapping a class linked with two other classes
(AttributeError: 'str' object has no attribute '_sa_instance_state')
Hi List,
I have a user class, a contact class, and a googleID class.
the contact class has can have a googleID per user in the system. I'm
trying to map it out as follows:
# ArkContact - clientprojectshot module
orm.mapper(ArkContact, contacts_table, properties={
'notes': orm.relation(ArkNote,
Re: [sqlalchemy] mapping a class linked with two other classes (AttributeError: 'str' object has no attribute '_sa_instance_state')
Ack, ignore :). There was no direct relationship to the user at all, doh. So I'm passing that into the ArkUserContactGUID construction, and all works well. Thanks again for the help, much appreciated. Jules -- 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 sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
Re: [sqlalchemy] Accessing several databases
ah good to know, I'm always wondering why people get confused about things like
this...
On Jun 16, 2011, at 9:33 AM, Julian J. M. wrote:
Thank you very much. I'll try that.
I was confused by this howto:
http://turbogears.org/2.1/docs/main/MultipleDatabases.html
They call declarative_base() for each each database... I thought I
needed that for each AppProject instance...
Anyway, thanks agaon for the example. I'll let you know.
Julian.
On Thu, Jun 16, 2011 at 13:54, King Simon-NFHD78
simon.k...@motorolasolutions.com wrote:
-Original Message-
From: sqlalchemy@googlegroups.com [mailto:sqlalchemy@googlegroups.com]
On Behalf Of Julian J. M.
Sent: 16 June 2011 11:43
To: sqlalchemy
Subject: [sqlalchemy] Accessing several databases
Hello,
I'm intending to use sqalchemy with orm for loading and storing my
application's project files. Each sqlite database would be a project
file, that will have several tables.
I'd like to work with projects like this:
project1=AppProject(/tmp/pr1.sqlite);
project2=AppProject(/tmp/pr2.sqlite);
item1 = project1.getItem(5) # item1 should be and object of a mapped
class.
item1.value=test
anotheritem = project1.getNewItem()
anotheritem.value=this is new
# this should flush and commit the underlying session for project1,
#modifying item with id 5, and adding a new one
project1.commitEverything()
item2 = project2.getItem(8)
item2.value = another test
project2.commitEverything()
The problem i'm facing is how to create the engine, metadata, mapper,
session, and the orm classes for each AppProject instance.
I'm not sure if this is supported or even a good idea.
Thanks,
Julian J. M.
I think this should be pretty easy with a separate SQLAlchemy Session
per project. You would define all your mappers and so on without any
reference to a specific database:
##
# your_db_module.py
import sqlalchemy as sa
import sqlalchemy.orm as saorm
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()
class ProjectItem(Base):
__tablename__ = 'project_item'
id = sa.Column(sa.Integer, autoincrement=True, primary_key=True)
# other columns etc.
Then your AppProject class would look something like this:
##
# appproject.py
import sqlalchemy as sa
import sqlalchemy.orm as saorm
from your_db_module import ProjectItem
class AppProject(object):
def __init__(self, filename):
self.engine = sa.create_engine('sqlite://' + filename)
self.session = saorm.Session(bind=self.engine)
def get_item(self, id):
return self.session.query(ProjectItem).get(id)
Hope that helps,
Simon
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[sqlalchemy] Versioning and multi-level inheritance
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 !!
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Re: [sqlalchemy] Versioning and multi-level inheritance
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.
On Jun 16, 2011, at 11:20 AM, JPLaverdure wrote:
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 !!
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