SQLAlchemy 没有为多列 UniqueConstraint 生成正确的 SQL 语句 [英] SQLAlchemy not producing proper SQL statement for multi column UniqueConstraints

问题描述

以下是我尝试在 sqlalchemy 中实现多列唯一约束时所做的两种不同尝试，由于未生成正确的 SQL 语句，这两种尝试似乎都失败了.

尝试:

from sqlalchemy import Column, Integer, String, Text, ForeignKey, DateTime, create_engine, UniqueConstraint, Boolean来自 sqlalchemy.orm 的导入关系、backref、sessionmaker从 sqlalchemy.ext.declarative 导入 declarative_base从 sqlalchemy.interfaces 导入 PoolListener导入 sqlalchemy类外键监听器(池监听器):定义连接(自我，dbapi_con，con_record):db_cursor = dbapi_con.execute('pragma foreign_keys=ON')engine = create_engine(r"sqlite:///" + r"d:\\foo.db",listeners=[ForeignKeysListener()], echo = True)会话 = sessionmaker(绑定 = 引擎)ses = 会话()Base = declarative_base()打印 sqlalchemy.__version__类 Foo(Base):__tablename__ = "foo"id = 列(整数，primary_key=True)虚拟 = 列(整数，唯一 = 真)班级酒吧(基地):__tablename__ = "bar"id = 列(整数，primary_key=True)baz = Column(Integer, ForeignKey("foo.id"))qux = Column(Integer, ForeignKey("foo.id"))UniqueConstraint("baz", "qux")类 Cruft(Base):__tablename__ = "cruft"id = 列(整数，primary_key=True)bar = Column(Integer, ForeignKey("foo.id"))qux = Column(Integer, ForeignKey("foo.id"))__table_args = (UniqueConstraint("bar", "qux"),)Base.metadata.create_all(引擎)

输出:

<预><代码>>>>0.8.22013-05-09 16:25:42,677 信息 sqlalchemy.engine.base.Engine PRAGMA table_info("foo")2013-05-09 16:25:42,677 信息 sqlalchemy.engine.base.Engine ()2013-05-09 16:25:42,677 信息 sqlalchemy.engine.base.Engine PRAGMA table_info("bar")2013-05-09 16:25:42,677 信息 sqlalchemy.engine.base.Engine ()2013-05-09 16:25:42,677 信息 sqlalchemy.engine.base.Engine PRAGMA table_info("cruft")2013-05-09 16:25:42,677 信息 sqlalchemy.engine.base.Engine ()2013-05-09 16:25:42,677 信息 sqlalchemy.engine.base.Engine创建表 foo (id 整数非空，虚拟整数，主键 (id),独一无二(假人))2013-05-09 16:25:42,677 信息 sqlalchemy.engine.base.Engine ()2013-05-09 16:25:42,767 信息 sqlalchemy.engine.base.Engine COMMIT2013-05-09 16:25:42,769 信息 sqlalchemy.engine.base.Engine创建表格栏(id 整数非空，巴兹整数，qux整数，主键 (id),外键 (baz) 参考 foo (id),外键 (qux) 参考 foo (id))2013-05-09 16:25:42,769 信息 sqlalchemy.engine.base.Engine ()2013-05-09 16:25:42,838 信息 sqlalchemy.engine.base.Engine COMMIT2013-05-09 16:25:42,839 信息 sqlalchemy.engine.base.Engine创建表 cruft (id 整数非空，酒吧整数，qux整数，主键 (id),外键(bar) REFERENCES foo (id),外键 (qux) 参考 foo (id))2013-05-09 16:25:42,839 信息 sqlalchemy.engine.base.Engine ()2013-05-09 16:25:42,917 信息 sqlalchemy.engine.base.Engine COMMIT

有什么建议吗?

解决方案

在声明性表配置中使用 UniqueConstraint 时，需要使用 __table_args__ 属性(注意both 名称的两侧:

class Bar(Base):__tablename__ = "bar"__table_args__ = (UniqueConstraint("baz", "qux"),)id = 列(整数，primary_key=True)baz = Column(Integer, ForeignKey("foo.id"))qux = Column(Integer, ForeignKey("foo.id"))类 Cruft(Base):__tablename__ = "cruft"__table_args__ = (UniqueConstraint("bar", "qux"),)id = 列(整数，primary_key=True)bar = Column(Integer, ForeignKey("foo.id"))qux = Column(Integer, ForeignKey("foo.id"))

属性必须是元组或字典.

现在创建这两个表的结果是:

2013-05-09 13:38:44,180 INFO sqlalchemy.engine.base.Engine创建表 cruft (id 整数非空，酒吧整数，qux整数，主键 (id),唯一 (bar, qux),外键(bar) REFERENCES foo (id),外键 (qux) 参考 foo (id))...2013-05-09 13:38:44,181 信息 sqlalchemy.engine.base.Engine创建表格栏(id 整数非空，巴兹整数，qux整数，主键 (id),独特 (baz, qux),外键 (baz) 参考 foo (id),外键 (qux) 参考 foo (id))

另请参阅 在使用声明性 ORM 扩展时设置约束部分定义约束和索引一章.

Below are the two different attempts I have made in trying to achieve a multi-column unique constraint in sqlalchemy, both of which seems to have failed since a proper SQL statement is not being produced.

The attempts:

from sqlalchemy import Column, Integer, String, Text, ForeignKey, DateTime, create_engine, UniqueConstraint, Boolean
from sqlalchemy.orm import relationship, backref, sessionmaker
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.interfaces import PoolListener
import sqlalchemy

class ForeignKeysListener(PoolListener):
    def connect(self, dbapi_con, con_record):
        db_cursor = dbapi_con.execute('pragma foreign_keys=ON')

engine = create_engine(r"sqlite:///" + r"d:\\foo.db",
                       listeners=[ForeignKeysListener()], echo = True)
Session = sessionmaker(bind = engine)
ses = Session()
Base = declarative_base()
print sqlalchemy.__version__
class Foo(Base):
    __tablename__ = "foo"

    id = Column(Integer, primary_key=True)
    dummy = Column(Integer, unique = True)
class Bar(Base):
    __tablename__ = "bar"
    id = Column(Integer, primary_key=True)
    baz = Column(Integer, ForeignKey("foo.id"))
    qux = Column(Integer, ForeignKey("foo.id"))
    UniqueConstraint("baz", "qux")

class Cruft(Base):
    __tablename__ = "cruft"

    id = Column(Integer, primary_key=True)
    bar = Column(Integer, ForeignKey("foo.id"))
    qux = Column(Integer, ForeignKey("foo.id"))
    __table_args = (UniqueConstraint("bar", "qux"),)
Base.metadata.create_all(engine)

The output:

>>> 0.8.2
2013-05-09 16:25:42,677 INFO sqlalchemy.engine.base.Engine PRAGMA table_info("foo")
2013-05-09 16:25:42,677 INFO sqlalchemy.engine.base.Engine ()
2013-05-09 16:25:42,677 INFO sqlalchemy.engine.base.Engine PRAGMA table_info("bar")
2013-05-09 16:25:42,677 INFO sqlalchemy.engine.base.Engine ()
2013-05-09 16:25:42,677 INFO sqlalchemy.engine.base.Engine PRAGMA table_info("cruft")
2013-05-09 16:25:42,677 INFO sqlalchemy.engine.base.Engine ()
2013-05-09 16:25:42,677 INFO sqlalchemy.engine.base.Engine 
CREATE TABLE foo (
    id INTEGER NOT NULL, 
    dummy INTEGER, 
    PRIMARY KEY (id), 
    UNIQUE (dummy)
)


2013-05-09 16:25:42,677 INFO sqlalchemy.engine.base.Engine ()
2013-05-09 16:25:42,767 INFO sqlalchemy.engine.base.Engine COMMIT
2013-05-09 16:25:42,769 INFO sqlalchemy.engine.base.Engine 
CREATE TABLE bar (
    id INTEGER NOT NULL, 
    baz INTEGER, 
    qux INTEGER, 
    PRIMARY KEY (id), 
    FOREIGN KEY(baz) REFERENCES foo (id), 
    FOREIGN KEY(qux) REFERENCES foo (id)
)


2013-05-09 16:25:42,769 INFO sqlalchemy.engine.base.Engine ()
2013-05-09 16:25:42,838 INFO sqlalchemy.engine.base.Engine COMMIT
2013-05-09 16:25:42,839 INFO sqlalchemy.engine.base.Engine 
CREATE TABLE cruft (
    id INTEGER NOT NULL, 
    bar INTEGER, 
    qux INTEGER, 
    PRIMARY KEY (id), 
    FOREIGN KEY(bar) REFERENCES foo (id), 
    FOREIGN KEY(qux) REFERENCES foo (id)
)


2013-05-09 16:25:42,839 INFO sqlalchemy.engine.base.Engine ()
2013-05-09 16:25:42,917 INFO sqlalchemy.engine.base.Engine COMMIT

Any suggestions?

解决方案

When using a UniqueConstraint in a declarative table configuration, you need to specify it using the __table_args__ attribute (note the underscores on both sides of the name:

class Bar(Base):
    __tablename__ = "bar"
    __table_args__ = (UniqueConstraint("baz", "qux"),)

    id = Column(Integer, primary_key=True)
    baz = Column(Integer, ForeignKey("foo.id"))
    qux = Column(Integer, ForeignKey("foo.id"))

class Cruft(Base):
    __tablename__ = "cruft"
    __table_args__ = (UniqueConstraint("bar", "qux"),)

    id = Column(Integer, primary_key=True)
    bar = Column(Integer, ForeignKey("foo.id"))
    qux = Column(Integer, ForeignKey("foo.id"))

The attribute must be either a tuple or a dictionary.

Creating these two tables now results in:

2013-05-09 13:38:44,180 INFO sqlalchemy.engine.base.Engine 
CREATE TABLE cruft (
    id INTEGER NOT NULL, 
    bar INTEGER, 
    qux INTEGER, 
    PRIMARY KEY (id), 
    UNIQUE (bar, qux), 
    FOREIGN KEY(bar) REFERENCES foo (id), 
    FOREIGN KEY(qux) REFERENCES foo (id)
)

...

2013-05-09 13:38:44,181 INFO sqlalchemy.engine.base.Engine 
CREATE TABLE bar (
    id INTEGER NOT NULL, 
    baz INTEGER, 
    qux INTEGER, 
    PRIMARY KEY (id), 
    UNIQUE (baz, qux), 
    FOREIGN KEY(baz) REFERENCES foo (id), 
    FOREIGN KEY(qux) REFERENCES foo (id)
)

Also see the Setting up Constraints when using the Declarative ORM Extension section of the Defining Constraints and Indexes chapter.

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