Question

I’m using python-storm as orm. The many-to-many reference set is giving me headaches 🙁

These are the relevant objects:

class Author(object):
    __storm_table__ = "author"
    id = Int(primary=True)
    name = Unicode()
    institution_id = Int()
    institution = Reference(institution_id, Institution.id)

    def __init__(self, name):
        self.name = name


class Paper(object):
    __storm_table__ = "paper"
    id = Int(primary=True)
    name = Unicode()
    conference_id = Int()
    conference = Reference(conference_id, Conference.id)

    def __init__(self, name):
        self.name = name

class AuthorPapers(object):
    __storm_table__ = "authorpapers"
    __storm_primary__ = "author_id", "paper_id"
    author_id = Int()
    paper_id = Int()

The respective sqlite table look like this

store.execute("CREATE TABLE if not exists author (id INTEGER PRIMARY KEY, name VARCHAR, institution_id INTEGER, FOREIGN KEY (institution_id) REFERENCES institution(id))")

store.execute("CREATE TABLE if not exists paper (id INTEGER PRIMARY KEY, name VARCHAR, conference_id INTEGER, FOREIGN KEY (conference_id) REFERENCES conference(id))")

store.execute("CREATE TABLE if not exists authorpapers (author_id INTEGER, paper_id INTEGER, PRIMARY KEY (author_id, paper_id))")

Now say if a have two author the collaborated on a paper

a = Author(u"Steve Rogers")
b = Author(u"Captain America")

and a paper

p6 = Paper(u"Bunga Bunga")

So now I want to associate both author to the paper using

Author.papers = ReferenceSet(Author.id, AuthorPapers.author_id, Paper.id, AuthorPapers.paper_id)

and doing this

a.papers.add(p6)
b.papers.add(p6)

This is btw it says it is supposed to work in the storm tutorial…but I get

  File "/usr/lib64/python2.7/site-packages/storm/references.py", line 376, in add
    self._relation2.link(remote, link, True)
  File "/usr/lib64/python2.7/site-packages/storm/references.py", line 624, in link
    pairs = zip(self._get_local_columns(local.__class__),
  File "/usr/lib64/python2.7/site-packages/storm/references.py", line 870, in _get_local_columns
    for prop in self.local_key)
  File "/usr/lib64/python2.7/site-packages/storm/references.py", line 870, in <genexpr>
    for prop in self.local_key)
  File "/usr/lib64/python2.7/site-packages/storm/properties.py", line 53, in __get__
    return self._get_column(cls)
  File "/usr/lib64/python2.7/site-packages/storm/properties.py", line 97, in _get_column
    attr = self._detect_attr_name(cls)
  File "/usr/lib64/python2.7/site-packages/storm/properties.py", line 82, in _detect_attr_name
    raise RuntimeError("Property used in an unknown class")
RuntimeError: Property used in an unknown class

And I’m not really able to make sense of this right now.

Answer 1

I’m not really, familiar with storm, but looking at the documentation example, looks like is just an issue related to the order in which the arguments to ReferenceSet are passed. I tried to use this:

Author.papers = ReferenceSet(Author.id, AuthorPapers.author_id, AuthorPapers.paper_id, Paper.id)

instead of this:

Author.papers = ReferenceSet(Author.id, AuthorPapers.author_id, Paper.id, AuthorPapers.paper_id)

and no exception was raised.