通过Flask-sqlalchemy中的订单号保持数据在db中的排序

如何解决通过Flask-sqlalchemy中的订单号保持数据在db中的排序

我有一个db（sqlite），其中包含防火墙和策略规则定义。而且我需要将每个记录保持在其防火墙中。我的防火墙和PolicyRule模型之间的关系是多对多的。所以我将等级（订单号）存储在关联模型中。即使我在记录中间插入数据，如何保持它们有序？

例如：

我以order_by的顺序获取记录：

1- Rule A 
2- Rule B 
3- Rule C 

然后我想在规则B和规则C之间添加规则D。所以我的下一个查询结果必须是这样的：

1- Rule A
2- Rule B
3- Rule D
4- Rule C

我需要知道规则的确切顺序，因为我将规则应用于iptables，并且iptables策略必须与用户完全相同的顺序。

这是我的模特：

class PolicyRule(db.Model):
    __tablename__ = 'policy_rule'
    id = db.Column(db.Integer(),primary_key=True)
    active = db.Column('is_active',db.Boolean(),nullable=False,server_default='1')
    name = db.Column(db.String(255,collation='NOCASE'),unique=True)
    rule_type = db.Column(db.String(255,nullable=False) # IPv4 or IPv6
    direction = db.Column(db.Text())
    action = db.Column(db.Text())
    comment = db.Column(db.Text())
    log = db.Column(db.Boolean(),server_default='1')
    firewalls = db.relationship("FwPolicyRules",back_populates="rule")

    # Foreign key assignments for relationships
    src_addr_id = db.Column(db.Integer(),db.ForeignKey(Address.id,ondelete='CASCADE'))
    dst_addr_id = db.Column(db.Integer(),ondelete='CASCADE'))
    src_service_id = db.Column(db.Integer(),db.ForeignKey(Service.id,ondelete='CASCADE'))
    dst_service_id = db.Column(db.Integer(),ondelete='CASCADE'))
    interface_id = db.Column(db.Integer(),db.ForeignKey(Interface.id,ondelete='CASCADE'))
    time_profile_id = db.Column(db.Integer(),db.ForeignKey(TimeProfile.id,ondelete='CASCADE'))
    
    # Relationship definitions for access the objects directly like "policy_rule.src_addr".
    src_addr = db.relationship("Address",foreign_keys=[src_addr_id],lazy='subquery',backref=db.backref("policy_src_addr",uselist=True))
    src_port = db.relationship("Service",foreign_keys=[src_service_id],backref=db.backref("policy_src_port",uselist=True))
    dst_addr = db.relationship("Address",foreign_keys=[dst_addr_id],backref=db.backref("policy_dst_addr",uselist=True))
    dst_port = db.relationship("Service",foreign_keys=[dst_service_id],backref=db.backref("policy_dst_port",uselist=True))
    interface = db.relationship("Interface",foreign_keys=[interface_id],backref=db.backref("policy_interface",uselist=True))
    time_profile = db.relationship("TimeProfile",foreign_keys=[time_profile_id],backref=db.backref("policy_time_profile",uselist=True))


class Firewall(db.Model):
    __tablename__ = 'firewall'
    id = db.Column(db.Integer(),primary_key=True)
    name = db.Column(db.String(255,unique=True)

    policy_rules = db.relationship("FwPolicyRules",back_populates="firewall",cascade="delete-orphan")
    nat_rules = db.relationship("FwNatRules",cascade="delete-orphan")
    routing_rules = db.relationship("FwRoutingRules",cascade="delete-orphan")

    interfaces = db.relationship('Interface',secondary=interfaces,backref=db.backref('used_firewalls',lazy=True,uselist=True))

class FwPolicyRules(db.Model):
    __tablename__ = 'fw_policy_rules'

    id = db.Column(db.Integer,primary_key=True)
    firewall_id = db.Column(db.Integer,db.ForeignKey('firewall.id',ondelete='cascade'))
    policy_rule_id = db.Column(db.Integer,db.ForeignKey('policy_rule.id',ondelete='cascade'))
    rank = db.Column(db.Integer,autoincrement=True)
    rule = db.relationship("PolicyRule",back_populates="firewalls",lazy='subquery')
    firewall = db.relationship("Firewall",back_populates="policy_rules",lazy='subquery')

编辑：我认为尽管有很多解释，但没人能完全理解我的问题。为了清楚起见，我想要这个的多对多版本： https://docs.sqlalchemy.org/en/13/orm/extensions/orderinglist.html

解决方法

最后我找到了孤独感

这是我使用python的方式：

我使用以下命令导入了订购列表：

from sqlalchemy.ext.orderinglist import ordering_list

，然后我修改了防火墙模型并添加了默认的order_by参数。之后， collection_class = ordering_list（'rank'）参数就完成了。

class Firewall(db.Model):
__tablename__ = 'firewall'
id = db.Column(db.Integer(),primary_key=True)
name = db.Column(db.String(255,collation='NOCASE'),nullable=False,unique=True)

policy_rules = db.relationship("FwPolicyRules",back_populates="firewall",lazy='subquery',cascade="save-update,merge,delete,delete-orphan",order_by="FwPolicyRules.rank",collection_class=ordering_list('rank'))
nat_rules = db.relationship("FwNatRules",order_by="FwNatRules.rank",collection_class=ordering_list('rank'))
routing_rules = db.relationship("FwRoutingRules",order_by="FwRoutingRules.rank",collection_class=ordering_list('rank'))

interfaces = db.relationship('Interface',secondary=interfaces,backref=db.backref('used_firewalls',lazy=True,uselist=True))

然后我就这样向防火墙添加新规则：

db.session.autoflush = False # This is important because of "cascade = delete-orphan" parameter. Otherwise PolicyRule will be deleted before its added.
new_rule = PolicyRule(...)
a = FwPolicyRules(rule=new_rule)
fw.policy_rules.insert(rank,a) # Alternatively you can use "fw.policy_rules.append(a)" for auto add rule to the end
db.session.autoflush = True
db.session.commit()

为了更改现有规则的顺序，我编写了一个函数：

def change_rule_rank(rule_rank,new_rank):
    db.session.autoflush = False
    rule_assoc = fw.policy_rules.pop(rule_rank)
    a = FwPolicyRules(rule=rule_assoc.rule)
    fw.policy_rules.insert(new_rank,a)
    db.session.autoflush = True
    db.session.commit()

希望它对某人有帮助。