具有复杂匹配逻辑的sqlalchemy外键。

Question

I am trying to build a database with sqlalchemy.

I have two tables : flow and krbr .

from __future__ import print_function
import numpy as np
import pandas as pd
import sqlalchemy
from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String
import sqlalchemy_utils
from sqlalchemy_utils.types.ip_address import IPAddressType


Base = declarative_base()

## Define the tables schema

class Flow(Base):
    __tablename__ = 'flow'

    Id  = Column(Integer, primary_key=True)
    First = Column(Integer, index=True)
    Protocol  = Column(String(10))
    Src = Column(IPAddressType, index=True)
    SrcPort = Column(Integer)
    Dst = Column(IPAddressType, index=True)
    DstPort = Column(Integer)
    GroupId = Column(Integer)
    Port = Column(String(10))
    VPort = Column(Integer)
    IpTos = Column(String)
    VlanId = Column(String)
    VlanPri = Column(String)
    Application = Column(String(100))
    Packets = Column(Integer)
    Messages = Column(Integer)
    Bytes = Column(Integer)
    Last = Column(Integer)
    #LearnedIPs alertable 
    #LearnedIPs learned-ip
    #   u'LearnedIPs new-ips', u'LearnedIPs subnet-name',
    #   u'LearnedIPs timestamp-sec', u'LearnedIPs total-ips', u'SrcSubnet',
    #   u'DstSubnet'],
    # 'MPLS Exp'


class Krbr(Base):
    __tablename__ = 'krbr'
    Id  = Column(Integer, primary_key=True)
    Src = Column(IPAddressType, index=True)
    SrcPort = Column(Integer)
    Dst = Column(IPAddressType, index=True)
    DstPort = Column(Integer)
    TimeNs = Column(Integer)

To some of the rows in flow is associated one or more rows of krbr .

A row in krbr is associated with a row in flow if:

1) they have the same values of Src, Dst, SrcPort, DstPort

2) They are close in time. ie np.abs(Flow.first - Krbr.TimeNs/1000000000) < threshold

I am wondering what is the right approach to create a link between the two tables. ie given a row of one table I want to be able to get the rows of the other table.

I do not know much of sqlalchemy. I guess that I should define a foreign key but I do not know how to enforce such a complex relationship.

Answer 1

Here is a sample of 'Handling Multiple Join Paths':

from sqlalchemy import Integer, ForeignKey, String, Column
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import relationship

Base = declarative_base()

class Customer(Base):
    __tablename__ = 'customer'
    id = Column(Integer, primary_key=True)
    name = Column(String)

    billing_address_id = Column(Integer, ForeignKey("address.id"))
    shipping_address_id = Column(Integer, ForeignKey("address.id"))

    billing_address = relationship("Address")
    shipping_address = relationship("Address")

class Address(Base):
    __tablename__ = 'address'
    id = Column(Integer, primary_key=True)
    street = Column(String)
    city = Column(String)
    state = Column(String)
    zip = Column(String)

More info about 'Handling Multiple Join Paths' in you can find at SQLAlchemy 0.9 Documentation