[sqlalchemy] Strange lazy-load query
Hi everyone! I have an object graph like this: Invoice - Detail (one-to-many with cascade) - Product (many-to-one) - VAT (many-to-one) My problem is that sometimes if I have a Detail and try to read its Product, the triggered lazy-loading generates a query more complicated than necessary, having a LEFT OUTER JOIN on the VAT table too... Other times the lazy-loading query joins only Detail and Product. I think I'm doing something fishy here.. What could I check, to ensure that the lazy loading doesn't touch unneeded entities? Many thanks! (SQLAlchemy 0.6.6, PGSQL 8.3) -- 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] Strange lazy-load query
the left outer join means there is a lazy=False or lazy='joinedload' on the relationship, or in this case since its sporadic, the parent Invoice is likely being loaded with an option like joinedload(Product.vat).The options specified in Query get attached to lazy loaders later in the chain, if the given joinedload() chain doesn't start from the entity being queried (which is probably the case if the query uses joinedload() and not joinedload_all()). For those Product objects already in the identity map, this option would not take place. On Mar 7, 2011, at 8:13 AM, Joril wrote: Hi everyone! I have an object graph like this: Invoice - Detail (one-to-many with cascade) - Product (many-to-one) - VAT (many-to-one) My problem is that sometimes if I have a Detail and try to read its Product, the triggered lazy-loading generates a query more complicated than necessary, having a LEFT OUTER JOIN on the VAT table too... Other times the lazy-loading query joins only Detail and Product. I think I'm doing something fishy here.. What could I check, to ensure that the lazy loading doesn't touch unneeded entities? Many thanks! (SQLAlchemy 0.6.6, PGSQL 8.3) -- 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] Re: overriding DeclarativeBase and descriptors
thanks, I will start experimenting ... On Mar 5, 4:52 pm, Michael Bayer mike...@zzzcomputing.com wrote: On Mar 5, 2011, at 10:43 AM, farcat wrote: Hi, I am trying to implement polymorphism and multiple inheritance by: - adding a column to the parent class/table indicating the table from which the (polymorphic) class attribute object can be queried - adding the attribute name and the parent id to the child table/class to be able to find the attribute object in this table Now i want to use a descriptor and/or override __getattr__/__setattr__/ __getattribute__ to insert or get the correct (polymorphic) object from the correct table. What I was wondering was e.g. whether using a descriptor will inhibit SA from functioning correctly. Any tips to implement what i am trying to do would be very welcome. SQLAlchemy uses descriptors for all the mapped attributes and has several avenues to augmenting them with your own descriptors. __getattribute__ and __setattr__ work as expected, as does __getattr__ although that only applies to names that otherwise don't exist on the object. We encourage an extremely simple approach to descriptor access which is to name the columns in one way, and the descriptor in another. The synonym construct does this as does the newer hybrid attribute approach. Set and delete events can also be intercepted using the events module (new in 0.7 - in 0.6 use AttributeExtension). Cheers, Lars -- 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 athttp://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] difference for type BigInteger between 0.6.6 and 0. 7.0b2
from sqlalchemy import *
meta = MetaData()
stx_setup = Table(stx_setup, meta,
Column('id', BigInteger(display_width=20), primary_key=True, autoincrement=T
rue),
Column('cost_center', Integer(display_width=1), index=True, nullable=True),
Column('AdministratorLicense', String(length=16), nullable=True),
Column('MDDOLicense', String(length=16), nullable=True),
Column('DONLicense', String(length=16), nullable=True),
Column('AssessorLicense', String(length=16), nullable=True),
Column('VendorNumber', String(length=4), nullable=True),
Column('ContractNumber', String(length=9), nullable=True),
Column('HospiceContractNumber', String(length=9), nullable=True),
Column('ServiceGroup', String(length=1), nullable=True),
)
The above code work in 0.6.6 and gives an following error in 0.7b2
Traceback (most recent call last):
File simple.py, line 6, in module
Column('id', BigInteger(display_width=20), primary_key=True,
autoincrement=True),
TypeError: __init__() got an unexpected keyword argument 'display_width'
Did not see anything in the 0.7 migration notes about this.
Is this a bug ?
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Re: [sqlalchemy] difference for type BigInteger between 0.6.6 and 0. 7.0b2
display_width is a MySQL option so you'd want to use
sqlalchemy.dialects.mysql.BIGINT / mysql.INTEGER for that. Not sure why
0.6.6's base BigInteger type allows it.
On Mar 7, 2011, at 5:38 PM, Mike Bernson wrote:
from sqlalchemy import *
meta = MetaData()
stx_setup = Table(stx_setup, meta,
Column('id', BigInteger(display_width=20), primary_key=True,
autoincrement=T
rue),
Column('cost_center', Integer(display_width=1), index=True, nullable=True),
Column('AdministratorLicense', String(length=16), nullable=True),
Column('MDDOLicense', String(length=16), nullable=True),
Column('DONLicense', String(length=16), nullable=True),
Column('AssessorLicense', String(length=16), nullable=True),
Column('VendorNumber', String(length=4), nullable=True),
Column('ContractNumber', String(length=9), nullable=True),
Column('HospiceContractNumber', String(length=9), nullable=True),
Column('ServiceGroup', String(length=1), nullable=True),
)
The above code work in 0.6.6 and gives an following error in 0.7b2
Traceback (most recent call last):
File simple.py, line 6, in module
Column('id', BigInteger(display_width=20), primary_key=True,
autoincrement=True),
TypeError: __init__() got an unexpected keyword argument 'display_width'
Did not see anything in the 0.7 migration notes about this.
Is this a bug ?
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[sqlalchemy] Declarative Class registry ?
Hello, Given a scenario where you're using declarative_base(...) and defining classes Is there a way to ask SA what the mapper class (declarative) is for a given table by inspecting something in metadata[table_name] ? cheers James -- 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.
