SQLalchemy primaryjoin 属性在 Python 3.4 中不起作用（使用 Python 2.7 起作用）

Question

我最近尝试将我们的代码从 Python 2.7 升级到 Python 3.4。

在 Python 2.7 中这很简单：

class Maatje(CommonColumns):
    koppelvoorstellen = db.relationship("Koppelvoorstel",
                        primaryjoin="or_(Maatje.id == Koppelvoorstel.deelnemerID," \
                        + "Maatje.id == Koppelvoorstel.vrijwilligerID)",
                        cascade="all,delete-orphan")

但是使用 Python 3.4（和从源代码编译的 mod_wsgi 4.4 针对 Python 3.4）我在 Apache 2.4 错误日志中尝试查询 Maatje 时遇到错误：

[wsgi:error] [pid 6169] sqlalchemy.exc.ProgrammingError:      
(mysql.connector.errors.ProgrammingError) 1064 (42000): You have an     
error in your SQL syntax; check the manual that corresponds to your 
MySQL server version for the right syntax to use near '%(param_1)s = 
koppelvoorstel.`vrijwilligerID`' at line 3 [SQL: 'SELECT 
koppelvoorstel.id AS koppelvoorstel_id, koppelvoorstel.aangemaakt AS     
koppelvoorstel_aangemaakt, koppelvoorstel.gewijzigd AS 
koppelvoorstel_gewijzigd, koppelvoorstel.etag AS koppelvoorstel_etag, 
koppelvoorstel.`deelnemerID` AS `koppelvoorstel_deelnemerID`,    
koppelvoorstel.`vrijwilligerID` AS `koppelvoorstel_vrijwilligerID`, 
koppelvoorstel.akkoordvrijwilliger AS 
koppelvoorstel_akkoordvrijwilliger, koppelvoorstel.akkoorddeelnemer AS 
koppelvoorstel_akkoorddeelnemer, 
koppelvoorstel.redenafwijzingvrijwilliger AS 
koppelvoorstel_redenafwijzingvrijwilliger, 
koppelvoorstel.redenafwijzingdeelnemer AS 
koppelvoorstel_redenafwijzingdeelnemer, koppelvoorstel.stopdatum AS 
koppelvoorstel_stopdatum, koppelvoorstel.redenstoppenvrijwilliger AS 
koppelvoorstel_redenstoppenvrijwilliger, 
koppelvoorstel.redenstoppendeelnemer AS 
koppelvoorstel_redenstoppendeelnemer \\nFROM koppelvoorstel \\nWHERE %
(param_1)s = koppelvoorstel.`deelnemerID` OR %(param_1)s = 
koppelvoorstel.`vrijwilligerID`'] [parameters: {'param_1': 1}]

对我来说看起来像是完全有效的 SQL（我假设 \\n 将成为换行符）。我尝试了使用 phpMyAdmin（不带 \n）并填写了参数（a one）的 SQL 查询，它理解了查询并得出了有效的结果。

我尝试过以其他形式编写primaryjoin，例如不带字符串、带or_ 和带“|”作为或运算符。还尝试了in_-operator。

我正在使用带有 mod_wsgi 4.4、SQLalchemy 1.0.12 和 Flask-SQLalchemy 2.1 的 Ubuntu 14.04。

我正在使用python3-mysql.connector（用于 MySQL 连接器/Python 的 Ubuntu 软件包）。

如果我删除了一个相等比较（不管是哪一个）并且不使用or_-operator，那么它不会引发错误。但我都需要使用or_-operator。

2016 年 3 月 6 日： 现在我已经将问题隔离了一点。用python2.7运行以下代码没有问题：

from flask import Flask
from flask_sqlalchemy import SQLAlchemy

app = Flask(__name__)
app.config['SQLALCHEMY_ECHO'] = True
app.config['SQLALCHEMY_DATABASE_URI'] = 'mysql+mysqlconnector://username:password@127.0.0.1/primaryjoindb'
db = SQLAlchemy(app)

class Coupleproposal(db.Model):
    __tablename__ = 'coupleproposal'
    id = db.Column(db.Integer, primary_key=True)
    participantID = db.Column(db.Integer, db.ForeignKey('buddy.id'), nullable = False)
    volunteerID = db.Column(db.Integer, db.ForeignKey('buddy.id'), nullable = False)

    participant = db.relationship("Buddy", foreign_keys=[participantID])
    volunteer = db.relationship("Buddy", foreign_keys=[volunteerID])
    __table_args__ = (db.UniqueConstraint('participantID', 'volunteerID', name='_couple_uc'),)

class Buddy(db.Model):
    __tablename__ = 'buddy'
    id = db.Column(db.Integer, primary_key=True)
    coupleproposals = db.relationship("Coupleproposal", \
                    primaryjoin="(Buddy.id == Coupleproposal.participantID) | (Buddy.id == Coupleproposal.volunteerID)", \
                    cascade="all,delete-orphan")

db.create_all()
b1 = Buddy()
b2 = Buddy()
db.session.add(b1)
db.session.add(b2)
cp1 = Coupleproposal(participantID=1, volunteerID=1)
db.session.add(cp1)
db.session.commit()
for aBuddy in db.session.query(Buddy).all():
    print(aBuddy.id)
    print(aBuddy.coupleproposals)

但是用python3.4运行代码会抛出这个错误：

sqlalchemy.exc.ProgrammingError: (mysql.connector.errors.ProgrammingError) 1064 (42000): 你的 SQL 语法有错误；检查与您的 MySQL 服务器版本相对应的手册，以在第 3 行的 '%(param_1)s = coupleproposal.volunteerID' 附近使用正确的语法 [SQL: 'SELECT coupleproposal.id AS coupleproposal_id, coupleproposal.participantID AS coupleproposal_participantID, coupleproposal.volunteerID AS coupleproposal_volunteerID \nFROM coupleproposal \nWHERE %(param_1)s = coupleproposal.participantID OR %(param_1)s = coupleproposal.volunteerID'] [参数：{'param_1' : 1}]

Answer 1

如果我使用不同的连接器，如 pymysql，它会起作用。在这里回答（不是我，而是 SQLalchemy 的回购所有者）：https://bitbucket.org/zzzeek/sqlalchemy/issues/3669/primaryjoin-attribute-with-or_-operator