[sqlalchemy] Re: column_property with load_only and inheritance
Hi Michael, thank you for your quick response!
Yeah, it seems that I got confused about the "load_only" method - it
doesn't load at all. I've tried to put together an easier example to show
the problem. It seems that it is related to the joinedload.
import sqlalchemy.orm
import sqlalchemy.inspection
entity = model.session.query(
model.Asset
).options(
sqlalchemy.orm.joinedload(
'parent'
)
).first()
state = sqlalchemy.inspection.inspect(entity.parent)
for attribute in state.attrs:
is_loaded = (
attribute.loaded_value is not
sqlalchemy.orm.base.NO_VALUE
)
if is_loaded:
print attribute.key
And if I omit it, it load s fine. Here is a simplified version of my model:
class Context(Base):
'''Represent a context.'''
context_type = Column(Unicode(32), nullable=False)
__mapper_args__ = {
'polymorphic_on': context_type,
'polymorphic_identity': 'context'
}
@declared_attr
def __tablename__(cls):
return 'context'
name = Column(Unicode(255), default=u'', nullable=False)
@declared_attr
def id(cls):
return Column(CHAR(36), primary_key=True, default=lambda: str(uuid
()))
@classmethod
def __declare_last__(cls):
'''Return link expression query.'''
# Import this module.
from . import context
context = aliased(context.Context.__table__)
# My real use-case is more complicated and involves a lot of joinst
to other tables, but this example reproduces the
# issue.
cls.link = column_property(
sqlalchemy.select(
[context.c.name + ' ' + context.c.context_type],
from_obj=[context]
).where(
context.c.id == cls.id
).label('link')
)
class Task(Context):
'''Represent a task.'''
@declared_attr
def __tablename__(cls):
return 'task'
@declared_attr
def __table_args__(cls):
return {
'mysql_engine': 'InnoDB',
'mysql_charset': 'utf8'
}
taskid = Column(
types.CHAR(36),
ForeignKey('context.id'),
primary_key=True
)
__mapper_args__ = {
'polymorphic_identity': 'task'
}
class Asset(Base):
'''Represent an Asset.'''
@declared_attr
def __tablename__(cls):
return 'asset'
@declared_attr
def __table_args__(cls):
return {
'mysql_engine': 'InnoDB',
'mysql_charset': 'utf8'
}
context_id = sqlalchemy.Column(
sqlalchemy.CHAR(36), sqlalchemy.ForeignKey('context.id')
)
parent = relationship('Context', backref=backref('assets'))
I hope this example makes more sense. Can you see any obvious problems with
my approach and why it wouldn't work?
If I add the link as a declared_attr instead it does work:
@declared_attr
def link(cls):
return column_property(cls.name + ' ' + cls.context_type)
However, my real-life use-case link is more complicated and I need to do
imports that would cause circular import errors if I used declared_attr.
Best regards,
Mattias L
On Monday, November 2, 2015 at 3:16:07 PM UTC+1, Mattias Lagergren wrote:
>
> Hi,
>
> I'm trying to use load_only and joinedload on a relationship
> model.Asset.parent. The parent relation is polymorphic and can be either
> Task or Project with the common Base class called Context.
>
> import sqlalchemy.orm
> import sqlalchemy.inspection
>
> entity = model.session.query(
> model.Asset
> ).options(
> sqlalchemy.orm.joinedload('parent').load_only(
> 'context_type', 'name', 'link'
> )
> ).first()
>
> state = sqlalchemy.inspection.inspect(entity.parent)
> for attribute in state.attrs:
> is_loaded = (
> attribute.loaded_value is not
> sqlalchemy.orm.base.NO_VALUE
> )
> if is_loaded:
> print attribute.key
>
> # Output:
> id
> taskid
> name
> context_type
>
>
> The id, name and context_type is from Context. And taskid is primary key
> on the taskid and is a foreignkey to the context.id. As you can see
> "name" loads fine but "link" attribute is not loaded. The "link" column is
> added as a column_property to Context using a __declare_last__.
>
> These are simplified versions of the classes:
>
>
> class Context(Base):
> '''Represent a context.'''
> context_type = Column(Unicode(32), nullable=False)
>
> __mapper_args__ = {
> 'polymorphic_on': context_type,
> 'polymorphic_identity': 'context'
> }
>
> name = Column(Unicode(255), default=u'', nullable=False)
>
> @declared_attr
> def id(cls):
> return
[sqlalchemy] Re: N-Triples to MySQL
You probably need to ask this on an rdflib forum. Looking at your code, you're just tossing a SqlAlchemy engine into rdflib. You probably need to integrate some sort of plugin, such as https://github.com/RDFLib/rdflib-sqlalchemy -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.
[sqlalchemy] N-Triples to MySQL
Hey, I'm trying to convert a N-Triples/.nt file to MySQL,
with rdflib, sqlalchemy and mysql.connector with Python.
This is my code:
from rdflib import Graph
import sqlalchemy
#1.0.9
print(sqlalchemy.__version__)
engine = sqlalchemy.create_engine(
'mysql+mysqlconnector://root:@localhost:3306/ksaat', pool_recycle=3600)
connection = engine.connect()
#
print(connection)
g = Graph(engine, identifier="ksaat")
g.open(connection, create=True)
g.parse("input", format="nt")
g.store()
#3110284
print(len(g))
I'm getting this error message:
No plugin registered for
(Engine(mysql+mysqlconnector://root:***@localhost:3306/ksaat),
)
What can I do to make my code work?
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Re: [sqlalchemy] compare a object/instance against its data in the database
On 11/03/2015 03:21 PM, c.bu...@posteo.jp wrote: Is there a way to find out if a persistent sqlalchemy mapped object was modified? It means I recieve a object (persistent, with identiy) from the database. Then the user (maybe!) modify its data in a dialog-window. obj = session.query(MyClass).first() LetTheUserDoSomethingWithIt(obj) if obj.is_modified() Is there a way to find out if the object in memory/RAM was modified compared to its instance in the database itself? I don't want to compare each attribute against the data in the dialog-window. session.is_modified(obj) will do this for you: http://docs.sqlalchemy.org/en/rel_1_0/orm/session_api.html?highlight=is_modified#sqlalchemy.orm.session.Session.is_modified read the docs carefully, this method can be tricky. -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.
[sqlalchemy] SQLAlchemy: Database Access Using Python - Developer's Library book
I came across this during a search, and in the four different sites I've checked, I've seen four different release dates varying from 2008 to 2018, for example: http://www.amazon.com/SQLAlchemy-Database-Access-Developers-Library/dp/0132364670 (which has 2018 for the release date). So I'm curious... Is this a very old book (2008) or a book that has several years to be released (2018)? Does anyone actually know which of the various dates are most likely correct? :) (I've seen a few around May-June of 2016, which seems the most likely, but...) Given one of the authors of the book, I'm hoping I might be able to find out more here. :) -- Ken Lareau -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.
[sqlalchemy] compare a object/instance against its data in the database
Is there a way to find out if a persistent sqlalchemy mapped object was modified? It means I recieve a object (persistent, with identiy) from the database. Then the user (maybe!) modify its data in a dialog-window. obj = session.query(MyClass).first() LetTheUserDoSomethingWithIt(obj) if obj.is_modified() Is there a way to find out if the object in memory/RAM was modified compared to its instance in the database itself? I don't want to compare each attribute against the data in the dialog-window. -- -BEGIN PGP PUBLIC KEY BLOCK- Version: GnuPG v1 mQENBFQIluABCACfPwAhRAwFD3NXgv5CtVUGSiqdfJGVViVBqaKd+14E0pASA0MU G0Ewj7O7cGy/ZIoiZ0+lIEZmzJKHfuGwYhXjR/PhnUDrQIHLBvh9WuD6JQuULXfH kXtVm/i9wm76QAcvr2pwYgNzhcJntUHl2GcgnInYbZDeVmg+p9yIPJjuq73/lRS3 0/McgNoFOBhKK/S6STQuFyjr9OyJyYd1shoM3hmy+kg0HYm6OgQBJNg92WV9jwGe GzlipvEp2jpLwVsTxYir2oOPhfd9D1fC9F/l/3gXbfjd5GIIVrZFq2haZmoVeJ33 LJxo3RA5Tf9LoUeels1b4s9kFz6h7+AHERUpABEBAAG0IUNocmlzdGlhbiBCdWh0 eiA8YnVodHpAcG9zdGVvLmRlPokBPgQTAQIAKAUCVAiW4AIbAwUJAeEzgAYLCQgH AwIGFQgCCQoLBBYCAwECHgECF4AACgkQZLsXsAdRqOxNUAf/V/hDA5zGDpySuCEj DhjiVRK74J9Wd8gfH0WAf1Co5HZ24wZH8rgOIVIgXw8rWkOw/VA6xfdfT+64xjTY Fhkpbrk199nDzp72F7Jc4NC+x8xac2e3rK5ifSWhZx7L5A32pGYE+d16m3EEqImK D4gcZl38x9zdUnD4hHyXkIPz1uCfuMuGgWEnaUk4Wbj41CBZr3O0ABue6regV15U jaes8r+B8iCcY+0yP2kse+3iaCaMqNv5FgQZ9+b2Cql8pFkZJVtBVUw4GW3DWZJi du0O/YrC9TgS+xY9ht/MD2qSHwjcK1sdImjqBO7xP8TIOwKeYyDvGKnSO3EJ/sSA UPGEPrkBDQRUCJbgAQgA0k/Qg67CCUJE2/zuxBEoK4wLJpDRJzh8CQPZpjWx8VP0 KL892jwfxymXn8KNhuy1SgCBFSeV9jg4VZNWDlUGJc2lo82ajr9PzIsrQwu4lf0B zrUWV5hWepKu/kb8uSjx58YYfx0SFz4+9akX3Wwu9TUHntzL5Gk3Q26nnsr1xEJ+ VEumvCH9AE0Tk0K7dQpJ2/JcLuO+uhrpd/lHFDYVN5NsG3P015uFOkDI6N/xNFCj v95XNR93QlfKpK3qWlFGescfG+o/7Ub6s67/i/JoNbw0XgPEHmQfXpD7IHO4cu+p +ETb11cz+1mmi96cy98ID+uTiToJ8G//yD9rmtyxoQARAQABiQElBBgBAgAPBQJU CJbgAhsMBQkB4TOAAAoJEGS7F7AHUajs6sQH/iKs6sPc0vkRJLfbwrijZeecwCWF blo/jzIQ8jPykAj9SLjV20Xwqg3XcJyko8ZU6/zuRJq9xjlv9pZr/oVudQAt6v+h 2Cf4rKEjmau483wjMV2xjTXQhZi9+ttDbia4fgdmGtKsOicn5ae2fFXcXNPu3RiW sZKifWdokA6xqMW6iIG9YjjI5ShxngHWp2xfPscBFMDRtFOMags/Yx+YvwoyEZ4A dURYMFHFqpwILEc8hIzhRg1gq40AHbOaEdczS1Rr3T7/gS6eBs4u6HuY5g2Bierm lLjpspFPjMXwJAa/XLOBjMF2vsHPrZNcouNKkumQ36yq/Pm6DFXAseQDxOk= =PGP9 -END PGP PUBLIC KEY BLOCK- -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.
Re: [sqlalchemy] Created edge-case bug with `contains_eager`, can't reproduce
Ah ha!
I figured this out. It was a mix of a lazy eye and some peculiarities
between Postgres(live) and sqlite(test-case).
Given the query:
session.query(Foo).options(contains_eager('bar')).order_by(Foo.id.desc()).offset(0).limit(100).all()]
The SQL is (approx)
select foo.*, bar.* from foo, bar order by foo.id desc limit 100;
I didn't notice that there wasn't a `join` from foo to bar until I
reformatted the SQL.
SqlAlchemy just drops in the 'bar' on the query.
In such a case, shouldn't the library ideally:
• raise some error
or
• not add in the "join"
?
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