[sqlalchemy] No attribute of child relation contained in parent object
Hi,
I am just starting to use the relation between two tables.
The problem started with the child data not being written to the child
tables.
I played around, and now I am totally confused.
Maybe someone can shed some light on this.
I got these tables:
{{{
user_table = sa.Table('User', meta.metadata,
sa.Column('UserId', sa.types.Integer(),
primary_key=True),
sa.Column('UserDesc',sa.types.UnicodeText(),
default=u''),
)
userrealm_table = sa.Table('UserRealm', meta.metadata,
sa.Column('id', sa.types.Integer(), primary_key=True),
sa.Column('user_id',
sa.types.Integer(),ForeignKey('User.UserId')),
sa.Column('realm_id', sa.types.Integer(),
nullable=False )
)
}}}
I got the following classes:
{{{
class User(object):
def __init__(self, desc):
log.debug(' __init__(%s)' % desc)
self.UserDesc = serial
classe UserRealm(object):
def __init__(self, realm):
log.debug(setting realm_id to %i % realm)
self.realm_id = realm
}}}
A user may belong to several realms. All the relation stuff should be
done in the mappers:
{{{
orm.mapper(UserRealm, userrealm_table)
orm.mapper(User, user_table, properties={
'children':relationship(UserRealm,backref='user', cascade=save-
update)
})
}}}
Now I am at the point, that the User object contains no attribute
identifying the realm...
I thought this attribute should be generated by the relation
definition?
Any ideas on this?
Kind regards
Cornelius
--
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.
[sqlalchemy] Complex query (for me)
Dear all,
I've a situation where some tutors has some doctorates. Each doctorate
has to upload some reports. Each tutor has to approve reports of his
doctorates.
These are the tables and mappers:
members_table = Table('members', metadata,
Column('id', types.Integer, primary_key=True),
Column('lastname', types.Unicode(30), nullable=False),
Column('tutor_id', types.Integer, ForeignKey('members.id'),
nullable=True),
Column('removed', types.Boolean, default=False))
reports_table = Table('reports', metadata,
Column('id', types.Integer, primary_key=True),
Column('approved', types.Boolean, default=False),
Column('writer', types.Integer, ForeignKey('members.id'),
nullable=False))
mapper(Members, members_table,
properties={
'tutor': relation(Members, backref='doctorate',
remote_side=members_table.c.id)
})
mapper(Reports, reports_table,
properties={
'owner': relation(Members, backref='report')
})
I have to create a query to select all reports of all doctorates of a
tutor. Using the following query I'm able to have all doctorate of a
tutor.
result = Session.query(Members).filter(and_(Members.removed==False,
Members.tutor.has(Members.id==tutor_id))).all()
But I'm not able to select also the doctorate reports.
Thanks
--
---
(o_
(o_//\ Coltivate Linux che tanto Windows si pianta da solo.
(/)_ V_/_
+--+
| ENRICO MORELLI | email: more...@cerm.unifi.it |
| * * * *| phone: +39 055 4574269 |
| University of Florence| fax : +39 055 4574253 |
| CERM - via Sacconi, 6 - 50019 Sesto Fiorentino (FI) - ITALY|
+--+
--
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] Complex query (for me)
For the moment I solved using these query: doctorate = Session.query(Members).filter(and_(Members.removed==False, Members.tutor.has(id=tutor_id))).subquery() reports = Session.query(Reports, doctorate.c.id).outerjoin((doctorate, Reports.writer==doctorate.c.id)).order_by(Reports.id).all() # Only to obtain the objects related to the tutor reports = [reports[i][0] for i in range(len(reports)) if reports[i][1]] Are there other possibilities? Thanks -- --- (o_ (o_//\ Coltivate Linux che tanto Windows si pianta da solo. (/)_ V_/_ +--+ | ENRICO MORELLI | email: more...@cerm.unifi.it | | * * * *| phone: +39 055 4574269 | | University of Florence| fax : +39 055 4574253 | | CERM - via Sacconi, 6 - 50019 Sesto Fiorentino (FI) - ITALY| +--+ -- 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] No attribute of child relation contained in parent object
Hi List,
ok, i figured it out. My understanding of the documentation was a bit
different.
I really worked out this way. But
Thekey in the properties is the attribute name, that will be added to
the parent object.
So doing this
orm.mapper(User, user_table, properties={
'realms':relation(TokenRealm, backref=backref('user')
)
...will add an attribute User.realms.
Kind regards
Cornelius
Am 26.01.2011 11:45, schrieb cornelinux:
Hi,
I am just starting to use the relation between two tables.
The problem started with the child data not being written to the child
tables.
I played around, and now I am totally confused.
Maybe someone can shed some light on this.
I got these tables:
{{{
user_table = sa.Table('User', meta.metadata,
sa.Column('UserId', sa.types.Integer(),
primary_key=True),
sa.Column('UserDesc',sa.types.UnicodeText(),
default=u''),
)
userrealm_table = sa.Table('UserRealm', meta.metadata,
sa.Column('id', sa.types.Integer(), primary_key=True),
sa.Column('user_id',
sa.types.Integer(),ForeignKey('User.UserId')),
sa.Column('realm_id', sa.types.Integer(),
nullable=False )
)
}}}
I got the following classes:
{{{
class User(object):
def __init__(self, desc):
log.debug(' __init__(%s)' % desc)
self.UserDesc = serial
classe UserRealm(object):
def __init__(self, realm):
log.debug(setting realm_id to %i % realm)
self.realm_id = realm
}}}
A user may belong to several realms. All the relation stuff should be
done in the mappers:
{{{
orm.mapper(UserRealm, userrealm_table)
orm.mapper(User, user_table, properties={
'children':relationship(UserRealm,backref='user', cascade=save-
update)
})
}}}
Now I am at the point, that the User object contains no attribute
identifying the realm...
I thought this attribute should be generated by the relation
definition?
Any ideas on this?
Kind regards
Cornelius
signature.asc
Description: OpenPGP digital signature
[sqlalchemy] outerjoin
Hi, I have this subquery, which yields results sp_HeaderDetails = session.query( InvoiceCashFlowPerDocNum.sequence_id, InvoiceHeaderInfo.invoice_ref, InvoiceHeaderInfo.doc_num ) \ .filter( ( InvoiceCashFlowPerDocNum.doc_num == InvoiceHeaderInfo.doc_num ) ) \ .subquery() I then do a outerjoin on another query cashflows = session.query( CashflowEventDetail, sp_HeaderDetails ) \ .outerjoin( ( sp_HeaderDetails, and_(sp_HeaderDetails.c.sequence_id == CashflowEventDetail.sequence_id ) ) ) This above statement generates the following sql: SELECT cash_flow_event_detail.id FROM cash_flow_event_detail LEFT OUTER JOIN (SELECT invoice_cashflows.sequence_id AS sequence_id, invoice_header_information.invoice_ref AS invoice_ref, invoice_header_information.doc_num AS doc_num FROM invoice_cashflows, invoice_header_information WHERE invoice_cashflows.doc_num = invoice_header_information.doc_num) AS anon_1 ON anon_1.sequence_id = cash_flow_event_detail.sequence_id The above sql doesnt return any values if I run the sql in python. It also generates error when I run it in db artisan generating a missing keyword error. However, if I remove the keyword AS in clause AS anon_1, it succeeds in DbArtisan. Any help would be appreciated -- 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] outerjoin
On Jan 26, 2011, at 11:46 AM, Pankaj wrote: Hi, I have this subquery, which yields results sp_HeaderDetails = session.query( InvoiceCashFlowPerDocNum.sequence_id, InvoiceHeaderInfo.invoice_ref, InvoiceHeaderInfo.doc_num ) \ .filter( ( InvoiceCashFlowPerDocNum.doc_num == InvoiceHeaderInfo.doc_num ) ) \ .subquery() I then do a outerjoin on another query cashflows = session.query( CashflowEventDetail, sp_HeaderDetails ) \ .outerjoin( ( sp_HeaderDetails, and_(sp_HeaderDetails.c.sequence_id == CashflowEventDetail.sequence_id ) ) ) This above statement generates the following sql: SELECT cash_flow_event_detail.id FROM cash_flow_event_detail LEFT OUTER JOIN (SELECT invoice_cashflows.sequence_id AS sequence_id, invoice_header_information.invoice_ref AS invoice_ref, invoice_header_information.doc_num AS doc_num FROM invoice_cashflows, invoice_header_information WHERE invoice_cashflows.doc_num = invoice_header_information.doc_num) AS anon_1 ON anon_1.sequence_id = cash_flow_event_detail.sequence_id This doesn't make sense, your query has two different selectables passed to query() so should have at least all the columns from sp_HeaderDetails listed out in the columns clause, unless you're paraphrasing. The SQL is otherwise correct, unless you're on a platform such as Oracle which does not generate the AS keyword. SQLAlchemy does not generate AS when the statement is compiled against such a backend. If this is not the case, would need DB in use, version information, test case. -- 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.
[sqlalchemy] simple update without a session or mapping
I'm currently interfacing with an Oracle db using sqlalchemy without any sessions or mappings. Selects and inserts work great, but I'd like to be able to update a row without having to delete and reinsert it. # remove the id table.delete(table.c.id == row['id']).execute() # add it back with new value row['name'] = 'now frank' self.conn.execute(table.insert(), row) I realize there there's an update function in table, but I'm at a loss as to how to use the syntax for it. I'm just changing one or two non-primary-key values. All the examples I see use the ORM mappings with sessions, or use the update to change every field in a column. -- 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] simple update without a session or mapping
the docs for update() are at: tutorial: http://www.sqlalchemy.org/docs/core/tutorial.html#inserts-and-updates API: http://www.sqlalchemy.org/docs/core/expression_api.html#sqlalchemy.sql.expression.update On Jan 26, 2011, at 2:14 PM, Josh Stratton wrote: I'm currently interfacing with an Oracle db using sqlalchemy without any sessions or mappings. Selects and inserts work great, but I'd like to be able to update a row without having to delete and reinsert it. # remove the id table.delete(table.c.id == row['id']).execute() # add it back with new value row['name'] = 'now frank' self.conn.execute(table.insert(), row) I realize there there's an update function in table, but I'm at a loss as to how to use the syntax for it. I'm just changing one or two non-primary-key values. All the examples I see use the ORM mappings with sessions, or use the update to change every field in a column. -- 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. -- 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.
[sqlalchemy] autocommit on for DDL
Hello,
While working on a database test with nose, I dug into sqlalchemy 0.6.6 until I
found these lines:
class DDLElement(expression.Executable, expression.ClauseElement):
Base class for DDL expression constructs.
_execution_options = expression.Executable.\
_execution_options.union({'autocommit':True})
In my nose test against postgresql, I emit a bunch of DDL, perform the test and
then roll back the whole shebang which conveniently makes it look like I didn't
touch the database. Obviously, the emitted commits were getting in my way, so I
wrote this:
class NoCommitDDL(DDL):
def __init__(self,*args,**kw):
super(NoCommitDDL,self).__init__(*args,**kw)
unfrozen = dict(self._execution_options)
del unfrozen['autocommit']
self._execution_options = frozendict(unfrozen)
DDL = NoCommitDDL
I still feel like I am missing something though. I understand that PostgreSQL
is perhaps one of few databases to allow for transaction-aware DDL, but why is
a commit emitted for the DDL for any database, when the database makes it
implied anyway?
Thanks.
Cheers,
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] autocommit on for DDL
On Jan 26, 2011, at 5:16 PM, A.M. wrote:
Hello,
While working on a database test with nose, I dug into sqlalchemy 0.6.6 until
I found these lines:
class DDLElement(expression.Executable, expression.ClauseElement):
Base class for DDL expression constructs.
_execution_options = expression.Executable.\
_execution_options.union({'autocommit':True})
In my nose test against postgresql, I emit a bunch of DDL, perform the test
and then roll back the whole shebang which conveniently makes it look like I
didn't touch the database. Obviously, the emitted commits were getting in my
way, so I wrote this:
class NoCommitDDL(DDL):
def __init__(self,*args,**kw):
super(NoCommitDDL,self).__init__(*args,**kw)
unfrozen = dict(self._execution_options)
del unfrozen['autocommit']
self._execution_options = frozendict(unfrozen)
DDL = NoCommitDDL
I still feel like I am missing something though. I understand that PostgreSQL
is perhaps one of few databases to allow for transaction-aware DDL, but why
is a commit emitted for the DDL for any database, when the database makes it
implied anyway?
Several databases offer transactional DDL including Postgresql.SQLA doesn't
differentiate between these backends - it emits COMMIT after any statement that
it considers to be an autocommit statement. autocommit means, commit this
statement after completion, if a transaction is not in progress.
From this it follows that if you'd like to emit several DDL statements in a
transaction, the usage is no different for DDL expressions than for any other
kind of DML statement (i.e insert/update/delete). Use
connection.begin()/transaction.commit() as documented at:
http://www.sqlalchemy.org/docs/core/connections.html#using-transactions
.
autocommit is described right after that:
http://www.sqlalchemy.org/docs/core/connections.html#understanding-autocommit
Also the public API for _execution_options is the execution_options()
generative call:
http://www.sqlalchemy.org/docs/core/expression_api.html?highlight=execution_options#sqlalchemy.sql.expression.Executable.execution_options
.
--
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] autocommit on for DDL
On Jan 26, 2011, at 5:45 PM, Michael Bayer wrote:
From this it follows that if you'd like to emit several DDL statements in a
transaction, the usage is no different for DDL expressions than for any other
kind of DML statement (i.e insert/update/delete). Use
connection.begin()/transaction.commit() as documented at:
http://www.sqlalchemy.org/docs/core/connections.html#using-transactions
.
autocommit is described right after that:
http://www.sqlalchemy.org/docs/core/connections.html#understanding-autocommit
Also the public API for _execution_options is the execution_options()
generative call:
http://www.sqlalchemy.org/docs/core/expression_api.html?highlight=execution_options#sqlalchemy.sql.expression.Executable.execution_options
.
Thanks for the prodding- I figured out my bug. Here is sample code that
demonstrates a little surprise.
First, this code that emits:
BEGIN (implicit)
SELECT 1
ROLLBACK
=
from sqlalchemy.engine import create_engine
from sqlalchemy.orm.session import sessionmaker
from sqlalchemy.orm import scoped_session
from sqlalchemy.schema import DDL
engine = create_engine('postgresql://localhost/test',echo=True)
session = scoped_session(sessionmaker(bind=engine))
DDL(SELECT 1).execute(bind=session)
session.rollback()
=
and here is the buggy code which emits:
SELECT 1
COMMIT
from sqlalchemy.engine import create_engine
from sqlalchemy.orm.session import sessionmaker
from sqlalchemy.orm import scoped_session
from sqlalchemy.schema import DDL
engine = create_engine('postgresql://localhost/test',echo=True)
session = scoped_session(sessionmaker(bind=engine))
DDL(SELECT 1).execute(bind=engine)
session.rollback()
=
Can you spot the difference? The DDL in the first code is bound to the session
and the latter code mistakenly binds to the engine for execution resulting in
two different execution paths. In hindsight, I guess it makes sense, but it
certainly was not easy to find...
Cheers,
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] autocommit on for DDL
Well, I spoke too soon :( What is the mistake in the following sample code
which causes the COMMITs to be emitted? Setting autocommit to either True or
False emits the same SQL. I think this is a case of staring at the same code
too long causing brain damage- thanks for your patience and help!
from sqlalchemy.engine import create_engine
from sqlalchemy.orm.session import sessionmaker
from sqlalchemy.orm import scoped_session
from sqlalchemy.schema import DDL,MetaData,Table
engine = create_engine('postgresql://localhost/test',echo=True)
session = scoped_session(sessionmaker(bind=engine))
metadata = MetaData()
metadata.bind = engine
Table('test1',metadata)
Table('test2',metadata)
metadata.create_all()
2011-01-26 18:27:48,284 INFO sqlalchemy.engine.base.Engine.0x...6cd0 select
version()
2011-01-26 18:27:48,284 INFO sqlalchemy.engine.base.Engine.0x...6cd0 {}
2011-01-26 18:27:48,286 INFO sqlalchemy.engine.base.Engine.0x...6cd0 select
current_schema()
2011-01-26 18:27:48,286 INFO sqlalchemy.engine.base.Engine.0x...6cd0 {}
2011-01-26 18:27:48,288 INFO sqlalchemy.engine.base.Engine.0x...6cd0 select
relname from pg_class c join pg_namespace n on n.oid=c.relnamespace where
n.nspname=current_schema() and lower(relname)=%(name)s
2011-01-26 18:27:48,288 INFO sqlalchemy.engine.base.Engine.0x...6cd0 {'name':
u'test1'}
2011-01-26 18:27:48,290 INFO sqlalchemy.engine.base.Engine.0x...6cd0 select
relname from pg_class c join pg_namespace n on n.oid=c.relnamespace where
n.nspname=current_schema() and lower(relname)=%(name)s
2011-01-26 18:27:48,290 INFO sqlalchemy.engine.base.Engine.0x...6cd0 {'name':
u'test2'}
2011-01-26 18:27:48,291 INFO sqlalchemy.engine.base.Engine.0x...6cd0
CREATE TABLE test1 (
)
2011-01-26 18:27:48,291 INFO sqlalchemy.engine.base.Engine.0x...6cd0 {}
2011-01-26 18:27:48,292 INFO sqlalchemy.engine.base.Engine.0x...6cd0 COMMIT
2011-01-26 18:27:48,293 INFO sqlalchemy.engine.base.Engine.0x...6cd0
CREATE TABLE test2 (
)
2011-01-26 18:27:48,293 INFO sqlalchemy.engine.base.Engine.0x...6cd0 {}
2011-01-26 18:27:48,294 INFO sqlalchemy.engine.base.Engine.0x...6cd0 COMMIT
--
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] autocommit on for DDL
On Jan 26, 2011, at 6:10 PM, A.M. wrote:
Thanks for the prodding- I figured out my bug. Here is sample code that
demonstrates a little surprise.
First, this code that emits:
BEGIN (implicit)
SELECT 1
ROLLBACK
=
from sqlalchemy.engine import create_engine
from sqlalchemy.orm.session import sessionmaker
from sqlalchemy.orm import scoped_session
from sqlalchemy.schema import DDL
engine = create_engine('postgresql://localhost/test',echo=True)
session = scoped_session(sessionmaker(bind=engine))
DDL(SELECT 1).execute(bind=session)
that's some surprise - a Session was never intended to be used as a bind and
that argument on DDL.execute() is documented as expecting a Connection or
Engine. Its kind of just coincidence it happens to call .execute() on the
thing it gets and it works.Dynamic typing FTW I guess
--
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] autocommit on for DDL
On Jan 26, 2011, at 6:32 PM, A.M. wrote:
Well, I spoke too soon :( What is the mistake in the following sample code
which causes the COMMITs to be emitted? Setting autocommit to either True or
False emits the same SQL. I think this is a case of staring at the same code
too long causing brain damage- thanks for your patience and help!
from sqlalchemy.engine import create_engine
from sqlalchemy.orm.session import sessionmaker
from sqlalchemy.orm import scoped_session
from sqlalchemy.schema import DDL,MetaData,Table
engine = create_engine('postgresql://localhost/test',echo=True)
session = scoped_session(sessionmaker(bind=engine))
metadata = MetaData()
metadata.bind = engine
Table('test1',metadata)
Table('test2',metadata)
metadata.create_all()
metadata.create_all() looks at the bind attribute, then uses it to execute
each DDL statement. The bind here is an engine so it uses connectionless
execution. connectionless execution is usually autocommit as documented here:
http://www.sqlalchemy.org/docs/core/connections.html#connectionless-execution-implicit-execution
to emit create_all() in a transaction:
conn = engine.connect()
with conn.begin():
metadata.create_all(conn)
2011-01-26 18:27:48,284 INFO sqlalchemy.engine.base.Engine.0x...6cd0 select
version()
2011-01-26 18:27:48,284 INFO sqlalchemy.engine.base.Engine.0x...6cd0 {}
2011-01-26 18:27:48,286 INFO sqlalchemy.engine.base.Engine.0x...6cd0 select
current_schema()
2011-01-26 18:27:48,286 INFO sqlalchemy.engine.base.Engine.0x...6cd0 {}
2011-01-26 18:27:48,288 INFO sqlalchemy.engine.base.Engine.0x...6cd0 select
relname from pg_class c join pg_namespace n on n.oid=c.relnamespace where
n.nspname=current_schema() and lower(relname)=%(name)s
2011-01-26 18:27:48,288 INFO sqlalchemy.engine.base.Engine.0x...6cd0 {'name':
u'test1'}
2011-01-26 18:27:48,290 INFO sqlalchemy.engine.base.Engine.0x...6cd0 select
relname from pg_class c join pg_namespace n on n.oid=c.relnamespace where
n.nspname=current_schema() and lower(relname)=%(name)s
2011-01-26 18:27:48,290 INFO sqlalchemy.engine.base.Engine.0x...6cd0 {'name':
u'test2'}
2011-01-26 18:27:48,291 INFO sqlalchemy.engine.base.Engine.0x...6cd0
CREATE TABLE test1 (
)
2011-01-26 18:27:48,291 INFO sqlalchemy.engine.base.Engine.0x...6cd0 {}
2011-01-26 18:27:48,292 INFO sqlalchemy.engine.base.Engine.0x...6cd0 COMMIT
2011-01-26 18:27:48,293 INFO sqlalchemy.engine.base.Engine.0x...6cd0
CREATE TABLE test2 (
)
2011-01-26 18:27:48,293 INFO sqlalchemy.engine.base.Engine.0x...6cd0 {}
2011-01-26 18:27:48,294 INFO sqlalchemy.engine.base.Engine.0x...6cd0 COMMIT
--
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.
--
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.
[sqlalchemy] generalized polymorphic mixin
Is it possible to make a generalized declarative mixin class that
abstracts away all of the syntax of inheritance? I've seen examples
that set up the __mapper_args__ but not the discriminator column, and
examples that set up the discriminator column but not the
__mapper_args__, but none with both.
This is roughly how I imagine it should work, but when I tried this,
rows were created with null values for the discriminator. A full
example is here:
https://gist.github.com/797893
class PolymorphicMixin(object):
@declared_attr
def discriminator(cls):
if Base in cls.__bases__:
return Column('discriminator', types.String(50))
for b in cls.__bases__:
if hasattr(b, 'discriminator'):
return b.discriminator
@declared_attr
def __mapper_args__(cls):
ret = {'polymorphic_identity': cls.__name__}
if Base in cls.__bases__:
ret['polymorphic_on'] = PolymorphicMixin.discriminator
return ret
Thanks,
Scott
--
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] generalized polymorphic mixin
well it will work if you say this:
class PolymorphicMixin(object):
discriminator = Column('discriminator', types.String(50))
@declared_attr
def __mapper_args__(cls):
ret = {'polymorphic_identity': cls.__name__}
if Base in cls.__bases__:
ret['polymorphic_on'] = cls.discriminator
return ret
This because, when declarative sees a plain Column on a mixin, it makes a copy
of it for the target class, then takes the step of placing that column into the
__mapper_args__ dictionary as a replacement for all occurrences of the original
column. This is one of the several tricks declarative uses to get mixins to
work (I was opposed to mixins for a long time for the reason of these tricks
being necessary).
When using a function to generate Column, it gets called once by declarative,
once by __mapper_args__(), we then have two Column objects that are totally
different. In 0.7 an error message is raised for this condition, I'd imagine
you tried 0.6 and it silently failed.
However, this approach of discriminator = Column at the class level doesn't
totally really work, since you'll see that it puts a discriminator column
on all the subclasses too. It sort of works out and gets populated on the
sub-table and all that but we don't really want that.
So we'll instead take advantage of memoizing on the class itself, replacing the
declared_attr with the column itself, and then it all works:
class PolymorphicMixin(object):
@declared_attr
def discriminator(cls):
if 'discriminator' in cls.__dict__:
return cls.discriminiator
else:
cls.discriminator = d = Column('discriminator', types.String(50))
return d
@declared_attr
def __mapper_args__(cls):
ret = {'polymorphic_identity': cls.__name__}
if Base in cls.__bases__:
ret['polymorphic_on'] = cls.discriminator
return ret
On Jan 26, 2011, at 8:30 PM, scott wrote:
Is it possible to make a generalized declarative mixin class that
abstracts away all of the syntax of inheritance? I've seen examples
that set up the __mapper_args__ but not the discriminator column, and
examples that set up the discriminator column but not the
__mapper_args__, but none with both.
This is roughly how I imagine it should work, but when I tried this,
rows were created with null values for the discriminator. A full
example is here:
https://gist.github.com/797893
class PolymorphicMixin(object):
@declared_attr
def discriminator(cls):
if Base in cls.__bases__:
return Column('discriminator', types.String(50))
for b in cls.__bases__:
if hasattr(b, 'discriminator'):
return b.discriminator
@declared_attr
def __mapper_args__(cls):
ret = {'polymorphic_identity': cls.__name__}
if Base in cls.__bases__:
ret['polymorphic_on'] = PolymorphicMixin.discriminator
return ret
Thanks,
Scott
--
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.
--
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.
[sqlalchemy] Multi-get?
Is there something similar to the .get() method in SqlSoup and Session but which allows me to fetch more than one object by ID, so as to save on round trips to the DB? (This could be done by composing using the IN operator in SQL.) Thanks in advance. -- Yang Zhang http://yz.mit.edu/ -- 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] Multi-get?
On Wed, Jan 26, 2011 at 8:17 PM, Yang Zhang yanghates...@gmail.com wrote: Is there something similar to the .get() method in SqlSoup and Session but which allows me to fetch more than one object by ID, so as to save on round trips to the DB? (This could be done by composing using the IN operator in SQL.) Thanks in advance. Did you try something like session.query(MyClass).filter(MyClass.id.in_([...list of ids...])).all() -- Mike Conley -- 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.
