Hi again,
While testing the complicated relationship from the other thread, I
noticed that I was generating a lot of queries that I couldn't
immediately explain. After a bit of digging, it turned out that it was
due to my use of code based on the "versioned objects" example at
http://docs.sqlalchemy.org/en/rel_0_9/_modules/examples/versioned_history/history_meta.html.
In the test script below we have 3 classes. Users belong to Companies,
and Companies reference a single Terms row. In the example, only the
Company class is versioned.
The test script inserts a single user, company and terms row, then in
new transaction loads the company and adds a new user. If you look at
the SQL output, you should see that it loads the company.terms
relationship, which doesn't seem like it should be necessary.
I think it's due to the following code from history_meta.py:
if not obj_changed:
# not changed, but we have relationships. OK
# check those too
for prop in obj_mapper.iterate_properties:
if isinstance(prop, RelationshipProperty) and \
attributes.get_history(obj, prop.key).has_changes():
for p in prop.local_columns:
if p.foreign_keys:
obj_changed = True
break
if obj_changed is True:
break
I can't figure out the circumstances when this should be necessary -
can someone explain it to me?
Thanks a lot,
Simon
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