Question

我有两个用于管理员和角色的表，与第三个表assignments（多对多关系）相关联，包含字段role_id，administrator_id和一些额外字段{{ 1}}和created_at，我想自动填充：

updated_at

但是当我为管理员分配角色时

assignments = db.Table('assignments',
    db.Column('role_id', db.Integer, db.ForeignKey('roles.id')),
    db.Column('administrator_id', db.Integer,
              db.ForeignKey('administrators.id')),
    db.Column('created_at', db.DateTime, server_default=db.func.now()),
    db.Column('updated_at', db.DateTime, server_default=db.func.now(),
              onupdate=db.func.now()),
    db.ForeignKeyConstraint(['administrator_id'], ['administrators.id']),
    db.ForeignKeyConstraint(['role_id'], ['roles.id'])
)

class Administrator(db.Model, UserMixin):
    __tablename__ = 'administrators'

    id = Column(Integer, primary_key=True, server_default=text("nextval('administrators_id_seq'::regclass)"))
    email = Column(String(255), nullable=False, unique=True, server_default=text("''::character varying"))
    name = Column(String(255))
    surname = Column(String(255))

    roles = db.relationship('Role', secondary=assignments,
                            backref=db.backref('users', lazy='dynamic'))


class Role(db.Model):
    __tablename__ = 'roles'

    id = Column(Integer, primary_key=True, server_default=text("nextval('roles_id_seq'::regclass)"))
    name = Column(String(255))

它因以下错误而中断：

admin.roles = [role1]
db.session.add(admin)
db.session.commit()

有没有办法为IntegrityError: (psycopg2.IntegrityError) null value in column "created_at" violates not-null constraint DETAIL: Failing row contains (1265, 19, 3, null, null). [SQL: 'INSERT INTO assignments (role_id, administrator_id) VALUES (%(role_id)s, %(administrator_id)s)'] [parameters: {'administrator_id': 19, 'role_id': 3}]表格中的created_at和updated_at字段设置默认值？

Answer 1

使用default和onupdate参数代替server_default和server_onupdate：

db.Column('created_at', db.DateTime, default=db.func.now()),
db.Column('updated_at', db.DateTime, default=db.func.now(),
          onupdate=db.func.now()),

Answer 2

试试这个

db.Column('created_at', db.DateTime, server_default=text("now()"))

设置关系表的server_default值

2 个答案: