On Jun 26, 2008, at 11:12 AM, bukzor wrote:
>
> Sorry for being a pest, but I've looked at the documentation and
> really can't figure this out. If a mapped class is a node of our
> graph, where do I find the edges, and how do I get to the next node.
the mapper has a method called "iterate_properties" which returns all
MapperProperty objects it contains. Each PropertyLoader subclass
represents a relation() to another mapper.
so you can walk among relations as follows:
recursive = set()
def walk (cls):
print "cls:", cls
if cls in recursive:
return
recursive.add(cls)
mapper = class_mapper(cls)
for prop in mapper.iterate_properties:
if isinstance(prop, PropertyLoader):
print "key", prop.key
walk(prop.mapper.class_)
>
> Alternatively, should I do this at the table/sql level rather than the
> class/orm level?
it depends on what information you're interested in. the use case
here seems to be joining among configured relation()s so the ORM level
would be better.
> How did you yourself learn this? Is there some other reference I'm
> overlooking?
heres the docs for every API mentioned above:
http://www.sqlalchemy.org/docs/05/sqlalchemy_orm.html#docstrings_sqlalchemy.orm_modfunc_class_mapper
http://www.sqlalchemy.org/docs/05/sqlalchemy_orm_mapper.html#docstrings_sqlalchemy.orm.mapper_Mapper
http://www.sqlalchemy.org/docs/05/sqlalchemy_orm_interfaces.html#docstrings_sqlalchemy.orm.interfaces_MapperProperty
http://www.sqlalchemy.org/docs/05/sqlalchemy_orm_properties.html#docstrings_sqlalchemy.orm.properties_PropertyLoader
The same documentation can be had by using "pydoc <modulename>", i.e.
pydoc sqlalchemy.orm.mapperlib
I also think you should consider carefully if you truly need
automatic, implicit joining across arbitrarily long paths. Its a
feature we explicitly removed for its non-pythonicness and
unpredictable behavior.
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