Hi all,
I have a model with three classes, Job, Page and PageVersions. A job
has many pages and a page has many versions.
Now, I use a combined primary key for Page and PageVersions (see code
below) - and have "normal" relations to each other (job.pages,
page.job, page.versions, pageversion.page etc.)
Only one version of a page is "active", and is marked so with a
boolean attribute on PageVersion. I would like to add a property on
Page that points to that version (this would of course create a
circular reference) - something like page.currentversion - with a
corresponding Integer column "currentversion" on the pages table.
Is this possible with SA given the kind of combined keys I'm using?
The fallback solution is to do an eager-load on all pageversions
attached to a page and handle this with a regular python property.
Arnar
jobs = Table("jobs", __meta__,
Column("jobno", Unicode(15), primary_key=True),
Column("created", DateTime, nullable=False,
default=datetime.now))
class Job(object):
pass
mapper(Job, jobs)
pages = Table("pages", __meta__,
Column("jobno", Unicode(15), ForeignKey("jobs.jobno"),
primary_key=True),
Column("pagename", Unicode(30), primary_key=True),
Column("created", DateTime, nullable=False,
default=datetime.now))
class Page(object):
pass
mapper(Page, pages, properties={
'job': relation(Job, backref=backref('pages', cascade="all, delete-orphan"))
})
pageversions = Table("pageversions", __meta__,
Column("jobno", Unicode(15), primary_key=True,
ForeignKey("pages.jobno")),
Column("pagename", Unicode(30), primary_key=True,
ForeignKey("pages.pagename")),
Column("version", Integer, primary_key=True),
Column("created", DateTime, nullable=False,
default=datetime.now),
Column("active", Boolean, nullable=False, default=True))
class PageVersion(object):
pass
mapper(PageVersion, pageversions, properties={
'page': relation(Page,backref=backref('versions', cascade="all,
delete-orphan",
lazy=False,
order_by=pageversions.c.version))
})
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