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I have a postgres database that looks something like this:

      Table "public.entities"
    Column     |            Type             |                   Modifiers                    
---------------+-----------------------------+------------------------------------------------
 id            | bigint                      | not null default nextval('guid_seq'::regclass)
 type_id       | smallint                    | not null
 name          | character varying           | 
Indexes:
    "entities_pkey" PRIMARY KEY, btree (id)
Foreign-key constraints:
    "entities_parent_id_fkey" FOREIGN KEY (parent_id) REFERENCES entities(id)
    "entities_type_id_fkey" FOREIGN KEY (type_id) REFERENCES entity_types(id)
Referenced by:
    TABLE "posts" CONSTRAINT "posts_id_fkey" FOREIGN KEY (id) REFERENCES entities(id)
    TABLE "posts" CONSTRAINT "posts_subject_1_fkey" FOREIGN KEY (subject_1) REFERENCES entities(id)
    TABLE "posts" CONSTRAINT "posts_subject_2_fkey" FOREIGN KEY (subject_2) REFERENCES entities(id)

    Table "public.posts"
  Column   |  Type  | Modifiers 
-----------+--------+-----------
 id        | bigint | not null
 poster_id | bigint | 
 subject_1 | bigint | not null 
 subject_2 | bigint | not null 
Indexes:
    "posts_pkey" PRIMARY KEY, btree (id)
Foreign-key constraints:
    "posts_id_fkey" FOREIGN KEY (id) REFERENCES entities(id)
    "posts_poster_id_fkey" FOREIGN KEY (poster_id) REFERENCES users(id)
    "posts_subject_1_fkey" FOREIGN KEY (subject_1) REFERENCES entities(id)
    "posts_subject_2_fkey" FOREIGN KEY (subject_2) REFERENCES entities(id)

I'm trying to figure out how to define the orm object for "posts" to include all 3 of the foreign keys. Notice only id is a primary key. The others are just relationships between posts and entities that are not to be pk'd.

class PostModel(EntitiesModel):
    __tablename__ = 'posts'

    id = db.Column(db.BigInteger, db.ForeignKey(EntitiesModel.id), primary_key=True, nullable=False)
    poster_id = db.Column(db.BigInteger, db.ForeignKey(UserModel.id), nullable=False)

    subject_1 = db.Column(db.BigInteger, db.ForeignKey(EntitiesModel.id), nullable=False)
    subject_2 = db.Column(db.BigInteger, db.ForeignKey(EntitiesModel.id), nullable=False)

I've tried fiddling with it a bit, and besides disabling the foreign keys on subject_1 I can't seem to come up with a solution that doesn't result in this error:

AmbiguousForeignKeysError: Can't determine join between 'entities' and 'posts'; tables have more than one foreign key constraint relationship between them. Please specify the 'onclause' of this join explicitly.

Any thoughts?

4

1 に答える 1

14

最も重要な部分を省略したため、正確に何が問題を引き起こしているのかは完全には明確ではありません-その例外をスローするコードですが、クラスPostModelに関係プロパティを追加すると、次のように関係呼び出しにforeign_keysパラメーターを追加しようとするスローが発生します:

class PostModel(...):
    # ...
    subject1_id = Column(db.Column(db.BigInteger, db.ForeignKey(EntitiesModel.id), nullable=False)
    subject2_id = Column(db.Column(db.BigInteger, db.ForeignKey(EntitiesModel.id), nullable=False)
    subject1 = relationship(EntitiesModel, foreign_keys=subject1_id)
    subject2 = relationship(EntitiesModel, foreign_keys=subject2_id)
于 2013-06-07T19:13:04.813 に答える