[sqlalchemy] Re: backref error when migrated to 0.4
Hello Bertrand,
It works like a charm, thanks a lot.
Max.
On 12/27/07, Bertrand Croq [EMAIL PROTECTED] wrote:
JobPosting's mapper tells RefdataLocation's mapper to add a property
named 'vacancies', then you tell RefdataLocation's mapper to add a
property
named 'vacancies'.
Replace these 2 lines by
mapper(
JobPosting,
jobad_posts_tbl,
properties = {
'jb_location': relation(
RefdataLocation,
backref = backref(
'vacancies',
order_by = desc(jobad_posts_tbl.c.published_date)
)
),
}
)
and it should work as expected.
--
Bertrand Croq
___
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14, rue Patis Tatelin Fax : +33 (0)223 21 21 60
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--
Max
http://maxischenko.in.ua // http://www.linkedin.com/in/maksim
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[sqlalchemy] Re: Is there a way to replace object in DB?
I think you're thinking of .load() .get() does not throw on not found. On 12/27/07, braydon fuller [EMAIL PROTECTED] wrote: you can also use 'try' to avoid error messages: def ensure_object(db, id): try: o = db.Query(ModelObject).get(id) except: o = ModelObject(1, u'title') db.save(o) db.commit() return o -Braydon Rick Morrison wrote: ...if you're just checking to see if something exists in the database, why not just try to .load() it, and then construct it afresh if you don't find it? This kind of operation is sometimes called an upsert ...some database engines support it, some don't. Most don't. But what all database engines DO support is a query, followed by either an insert, or an update as appropriate. Here's the idiom that should work: def ensure_object(sess, id): o = sess.Query(ModelObject).get(id)# if found, o is now loaded into session if not o: o = ModelObject(1, u'title' sess.save(o) sess.flush() return o --~--~-~--~~~---~--~~ 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 [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en -~--~~~~--~~--~--~---
[sqlalchemy] Re: Is there a way to replace object in DB?
On Dec 26, 2007 10:38 PM, Michael Bayer [EMAIL PROTECTED] wrote:
if you have an instance which you are unsure if it already exists, you
can add it to a session using session.save_or_update(instance). The
decision between INSERT and UPDATE is ultimately decided by the
presence of an attribute on the instance called _instance_key.
I'd like mapper to use UPDATE for newly constructed object (i.e.
object without _instance_key attribute) when a record with the same
primary key already exists in DB.
In most cases, this attribute is not something you need to worry about;
if an instance has been flushed or loaded from a session, it will have
the attribute, or if you've just constructed it and not yet persisted
it, the attribute will not be there. If you think you need to
manually manipulate this attribute, perhaps you can describe your
specific use case so that we can recommend the best way to accomplish
it.
OK, below is a use/test case:
---8---
import sqlalchemy as sa, logging
from sqlalchemy.orm import mapper, sessionmaker
logging.getLogger('sqlalchemy.engine').setLevel(logging.INFO)
logging.basicConfig()
class ModelObject(object):
def __init__(self, id, title):
self.id = id
self.title = title
metadata = sa.MetaData()
objectTable = sa.Table(
'Objects', metadata,
sa.Column('id', sa.Integer, primary_key=True),
sa.Column('title', sa.String(255), nullable=False),
)
objectsMapper = mapper(ModelObject, objectTable)
engine = sa.create_engine('sqlite://')
metadata.create_all(engine, checkfirst=True)
session = sessionmaker(bind=engine)()
obj = ModelObject(1, u'title')
session.save(obj)
session.commit()
session.clear()
# Another program. We have to insure that object with id=1 exists in DB and has
# certain properties.
obj = ModelObject(1, u'title')
session.save_or_update(obj)
session.commit()
---8---
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[sqlalchemy] Re: Is there a way to replace object in DB?
...if you're just checking to see if something exists in the database, why
not just try to .load() it, and then construct it afresh if you don't find
it?
This kind of operation is sometimes called an upsert ...some database
engines support it, some don't. Most don't. But what all database engines DO
support is a query, followed by either an insert, or an update as
appropriate.
Here's the idiom that should work:
def ensure_object(sess, id):
o = sess.Query(ModelObject).get(id)# if found, o is now loaded into
session
if not o:
o = ModelObject(1, u'title')
sess.save(o)
sess.flush()
return o
On 12/27/07, Denis S. Otkidach [EMAIL PROTECTED] wrote:
On Dec 26, 2007 10:38 PM, Michael Bayer [EMAIL PROTECTED] wrote:
if you have an instance which you are unsure if it already exists, you
can add it to a session using session.save_or_update(instance). The
decision between INSERT and UPDATE is ultimately decided by the
presence of an attribute on the instance called _instance_key.
I'd like mapper to use UPDATE for newly constructed object (i.e.
object without _instance_key attribute) when a record with the same
primary key already exists in DB.
In most cases, this attribute is not something you need to worry about;
if an instance has been flushed or loaded from a session, it will have
the attribute, or if you've just constructed it and not yet persisted
it, the attribute will not be there. If you think you need to
manually manipulate this attribute, perhaps you can describe your
specific use case so that we can recommend the best way to accomplish
it.
OK, below is a use/test case:
---8---
import sqlalchemy as sa, logging
from sqlalchemy.orm import mapper, sessionmaker
logging.getLogger('sqlalchemy.engine').setLevel(logging.INFO)
logging.basicConfig()
class ModelObject(object):
def __init__(self, id, title):
self.id = id
self.title = title
metadata = sa.MetaData()
objectTable = sa.Table(
'Objects', metadata,
sa.Column('id', sa.Integer, primary_key=True),
sa.Column('title', sa.String(255), nullable=False),
)
objectsMapper = mapper(ModelObject, objectTable)
engine = sa.create_engine('sqlite://')
metadata.create_all(engine, checkfirst=True)
session = sessionmaker(bind=engine)()
obj = ModelObject(1, u'title')
session.save(obj)
session.commit()
session.clear()
# Another program. We have to insure that object with id=1 exists in DB
and has
# certain properties.
obj = ModelObject(1, u'title')
session.save_or_update(obj)
session.commit()
---8---
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[sqlalchemy] Re: Is there a way to replace object in DB?
you can also use 'try' to avoid error messages: def ensure_object(db, id): try: o = db.Query(ModelObject).get(id) except: o = ModelObject(1, u'title') db.save(o) db.commit() return o -Braydon Rick Morrison wrote: ...if you're just checking to see if something exists in the database, why not just try to .load() it, and then construct it afresh if you don't find it? This kind of operation is sometimes called an upsert ...some database engines support it, some don't. Most don't. But what all database engines DO support is a query, followed by either an insert, or an update as appropriate. Here's the idiom that should work: def ensure_object(sess, id): o = sess.Query(ModelObject).get(id)# if found, o is now loaded into session if not o: o = ModelObject(1, u'title' sess.save(o) sess.flush() return o --~--~-~--~~~---~--~~ 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 [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en -~--~~~~--~~--~--~---
[sqlalchemy] filter_by() related table columns
I am attempting to upgrade from sqlalchemy 0.3.11 to current release
0.4.1 and i am getting the following error:
/recs = session.query(PurchaseOrder).filter_by(description =
'Shipped').all()
File C:\Python24\Lib\site-packages\sqlalchemy\orm\query.py, line
322, in filter_by
clauses = [self._joinpoint.get_property(key,
resolve_synonyms=True).compare(operator.eq, value)
File C:\Python24\Lib\site-packages\sqlalchemy\orm\mapper.py, line
192, in get_property
raise exceptions.InvalidRequestError(Mapper '%s' has no property
'%s' % (str(self), key))
InvalidRequestError: Mapper 'Mapper|PurchaseOrder|purchaseorder' has
no property 'description'
/
I am trying to query a column in a related table with the following
query:
recs = session.query(PurchaseOrder).filter_by(description =
'Shipped').all()
This query works in 0.3.11.
Is there a new setting when defining relationships that I need to set
so that it looks at the related table columns when running a filter_by
or am i missing something simple?
Here is my simplified example classes, table definitions, and
mappings:
class PurchaseOrder(object) : pass
class OrderStatus(object) : pass
purchaseorder_table = sqlalchemy.Table(
'purchaseorder', metadata,
sqlalchemy.Column('id', sqlalchemy.Integer, primary_key=True),
sqlalchemy.Column('createdate', sqlalchemy.TIMESTAMP),
sqlalchemy.Column('statusid', sqlalchemy.Integer,
sqlalchemy.ForeignKey('testing.orderstatus.statusid')),
schema = 'testing')
orderstatus_table = sqlalchemy.Table( 'orderstatus',
metadata,
sqlalchemy.Column('statusid', sqlalchemy.Integer,
primary_key=True),
sqlalchemy.Column('description', sqlalchemy.VARCHAR),
schema = 'testing')
orm.mapper(PurchaseOrder,
purchaseorder_table,
properties={
'orderstatus' : orm.relation(OrderStatus)})
orm.mapper(OrderStatus,
orderstatus_table)
Thanks,
Curtis
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