Question

我有注释的版本控制系统

class Annotation(db.Model):
    id = db.Column(db.Integer, primary_key=True)

class AnnotationVersion(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    book_id = db.Column(db.Integer, db.ForeignKey("book.id"))
    previous_id = db.Column(db.Integer, db.ForeignKey("post_version.id"), default=None)
    pointer_id = db.Column(db.Integer, db.ForeignKey("annotation.id"))
    current = db.Column(db.Boolean, index=True)
    first_line_num = db.Column(db.Integer)
    last_line_num = db.Column(db.Integer)

class Line(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    book_id = db.Column(db.Integer, db.ForeignKey("book.id")
    line = db.Column(db.String(255))

我在Annotation类上具有以下两种关系：

lines = db.relationship("Line", secondary="annotation_version",
        primaryjoin="and_(Annotation.id==AnnotationVersion.pointer_id,"
            "AnnotationVersion.current==True)",
        secondaryjoin="and_(Line.l_num>=AnnotationVersion.first_line_num,"
            "Line.l_num<=AnnotationVersion.last_line_num,"
            "Line.book_id==AnnotationVersion.book_id)",
        viewonly=True, uselist=True)
context = db.relationship("Line", secondary="annotation_version",
        primaryjoin="and_(Annotation.id==AnnotationVersion.pointer_id,"
            "AnnotationVersion.current==True)",
        secondaryjoin="and_(Line.l_num>=AnnotationVersion.first_line_num-5,"
            "Line.l_num<=AnnotationVersion.last_line_num+5,"
            "Line.book_id==AnnotationVersion.book_id)",
        viewonly=True, uselist=True)

如您所见，上下文仅仅是first_line_num-5和last_line_num+5；换句话说，注释的上下文就是注释文本实际正文的前五行和后五行。

我正在尝试在实际的AnnotationVersion上定义相同的上下文关系：

context = db.relationship("Line",
    primaryjoin="and_(Line.l_num>=AnnotationVersion.first_line_num-5,"
        "Line.l_num<=AnnotationVersion.last_line_num+5,"
        "Line.book_id==AnnotationVersion.book_id)",
        viewonly=True, uselist=True)

但是这个确切的定义总是返回失败

sqlalchemy.exc.ArgumentError：无法找到任何相关的外部文件主要联接条件'line.l_num> =的关键列注解版本.first_line_num-：first_line_num_1和line.l_num <=注解version.last_line_num +：last_line_num_1 AND line.book_id =注解version.book_id'关于关系 AnnotationVersion.context。确保引用列是与ForeignKey或ForeignKeyConstraint关联，或被注释在带有foreign（）注释的连接条件中。

如果我删除了+5或-5，它将起作用。但是，一旦我同时定义了两者，就会收到该错误。

到底是什么原因导致此特殊故障？如您所见，它仅在primaryjoin条件中定义时才会发生，因为它完美地用作secondaryjoin条件。

Answer 1

Ilja Everila对文档的引用帮助解决了它。我要做的就是指定foreign_key参数：

context = db.relationship("Line",
    primaryjoin="and_(Line.l_num>=AnnotationVersion.first_line_num-5,"
        "Line.l_num<=AnnotationVersion.last_line_num+5,"
        "Line.book_id==AnnotationVersion.book_id)",
        foreign_keys=[first_line_num, last_line_num],
        viewonly=True, uselist=True)

primaryjoin和_中的两个算术运算会导致失败

1 个答案: