When I delete[*1] a mapped object (a Title()) that is on the many side
of a 1:m relationship (in sqlalchemy 0.8.0b2, Python 3.3), I get the
following error when I do a session.commit():
[...earlier part of traceback elided...]
File "/usr/local/lib/python3.3/site-packages/sqlalchemy/orm/sync.py",
line 53, in clear
(r, orm_util.state_str(dest))
AssertionError: Dependency rule tried to blank-out primary key column
'title.work' on instance '<Title at 0xb5130d8c>'
The relationship is set up as:
class Work: pass
class Title: pass
t_work = meta.tables['work']
sa.orm.mapper (Work, t_work,
properties={'titles': sa.orm.relationship (Title),
passive_deletes=True),
[...])
sa.orm.mapper (Title, meta.tables['title'])
The sqlalchemy "tables" are defined by calling
sqlalchemy.MetaData().reflect()
and the db tables "work" and "title" are defined in postgresql:
CREATE TABLE work (
id SERIAL PRIMARY KEY,
[...]
CREATE TABLE title (
work INT NOT NULL REFERENCES work(id) ON UPDATE CASCADE ON DELETE
CASCADE,
title SMALLINT NOT NULL DEFAULT 1,
PRIMARY KEY (work,title),
[...]
What does the error message mean? What rule? Why is SA trying
to "blank out" (whatever that means) some attributes on an object
that is going away anyway? But mostly: how do I fix?
----
[*1]
If it matters, I am deleting the Title() object like:
del Work.titles[2]
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