why did this come to me?
Mary
On 2/26/2010 5:03 PM, Kent wrote:
I'm pretty sure that I can use RelationProperty.synchronize_pairs
to tell me which fks I need on the parent.
To determine the class of the relation, I've worked this pseudo-code
out, but if there is a nicer way, please tell me:
if isinstance(RelationProperty.argument, Mapper):
cls = RelationProperty.argument.class_ #for backrefs, apparently
else:
cls = RelationProperty.argument
To get the order of the ident keys to pass to session.query().get():
class_mapper(cls).primary_key
Seems there might be an easier way, I'd very much like to hear it.
On Feb 26, 3:31 pm, Kent<[email protected]> wrote:
Also, it is feasible (or likely even) that the relation I am
attempting to query is already persistent in the session. Is .get()
the only function that attempts to find an unexpired persistent
instance before going to the database?
Will doing a session.query().filter() also check if the object is
persistent before querying the database (doubt that's possible?)?
On Feb 26, 3:23 pm, Kent<[email protected]> wrote:
It *sounds* like exactly what I'm looking for, but when I try a simple
example, it doesn't seem to work:
ol=OrderDetail()
ol.productid = 'DININGCHAIR'
DBSession.query(Product).with_parent(ol).all()
15:21:57,688 INFO [sqlalchemy.engine.base.Engine.0x...d3d0] BEGIN
15:21:57,694 INFO [sqlalchemy.engine.base.Engine.0x...d3d0] SELECT
products.productid AS products_productid, products.brand AS
products_brand, products.vendorsku AS products_vendorsku,
products.stockeditem AS products_stockeditem,
products.packagesplittype AS products_packagesplittype,
products.packagecomponent AS products_packagecomponent,
products.productgroup AS products_productgroup, products.productfamily
AS products_productfamily, products.productsubfamily AS
products_productsubfamily, products.description AS
products_description, products.regular AS products_regular,
products.commissiontype AS products_commissiontype,
products.replacementcost AS products_replacementcost, products.sale AS
products_sale, products.onhand AS products_onhand, products.onorder AS
products_onorder, products.imageurl AS products_imageurl,
products.special AS products_special, products.featured AS
products_featured, products.newproduct AS products_newproduct
FROM products
WHERE products.productid = %(param_1)s
15:21:57,694 INFO [sqlalchemy.engine.base.Engine.0x...d3d0]
{'param_1': None}
[]
I had expected the bind variable param_1 to equal the fk of
'DININGCHAIR'
What am I missing?
On Feb 26, 2:50 pm, Michael Bayer<[email protected]> wrote:
On Feb 26, 2010, at 1:48 PM, Kent wrote:
I'm certain sqlalchemy's got a function call in its guts that I was
about to recreate from scratch, so I'm hoping you can spare me the
trouble.
I'm trying to construct the foreign key where clause and from clause
needed to populate a relation.
I'd explain how I got here, but might take several days, so instead,
is there a function call to help me?
In other words, I've got an object, for example an order:
===================================
orderdetail_table = Table("orderdetails",metadata,
Column("orderid", Unicode, ForeignKey('orders.orderid'),
primary_key=True),
Column("lineid", Integer, primary_key=True),
Column("saleprice", Numeric, nullable=False),
Column("productid", Unicode(255),
ForeignKey('products.productid'), nullable=False)
)
product_table = Table("products", metadata,
Column("productid", Unicode(255), primary_key=True),
Column("brand", Unicode(255),
...
)
class Order(object):
pass
class OrderDetail(object):
pass
# ---------------------------- OrderDetail
-------------------------------------------------------- #
orderdetail_mapper = mapper(OrderDetail, orderdetail_table,
allow_null_pks=False,
properties=dict(product=relation(Product,
cascade='refresh-expire,expunge', #don't save
changes to Product
lazy=False)))
=====================
Say the 'product' relation is not populated on a *transient*
OrderDetail object that I will not be issuing a session flush() for
(there are errors detected.. but that's the long story).
I want to populate the transient OrderDetails 'product' attribute with
the detached product.
I assume there is no way a refresh of the 'product' attribute will
accomplish this since the parent obj is transient (which would really
be what I want), so I am also assuming I'll need to build the pk
clause and issue a session.query.get().
Since this is dynamic code (accepting any sqla object), I need to
dynamically construct that pk clause and from clause based on the
mapper's RelationProperty. In other words, use _foreign_keys to
construct this ?
But I imagine there is already a function call that will get me what I
want.
In the end, for this example, I'd want to dynamically build
session.query(Product).filter( * pk clause based on fks *)
Is there a function that can get me most everything I want (return the
pk clause) or must I build that up myself, and if myself, do you
recommend the RelationProperty's _foreign_keys attribute as the
starting point?
Thanks in advance, again.
are you perhaps looking for sess.query(Product).with_parent(someorder) ?
there's an example here:
http://www.sqlalchemy.org/docs/mappers.html#building-query-enabled-pr...
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