无法使用flask-sqlalchemy创建自动增量主键 [英] unable to create autoincrementing primary key with flask-sqlalchemy
问题描述
class Region(db.Model):
__tablename__ ='regions'
id = db.Column(db.Integer,primary_key = True,autoincrement = True)
name = db.Column(db.String(100))
parent_id = db.Column(db.Integer ,db.ForeignKey('regions.id'))
parent = db.relationship('Region',remote_side = id,primaryjoin =('Region.parent_id == Region.id'),backref ='sub- (db.DateTime,default = db.func.now())
deleted_at = db.Column(db.DateTime)
$ c $上面的代码创建了我的表,但是不会使 id
自动增量。所以,如果在我的插入查询中,我错过了 id
字段,它给了我这个错误
错误:列ID中的空值违反了非空约束
所以我改变了 id
声明看起来像这样
id = db.Column(db.Integer,db.Sequence('
同样的错误。上面的代码有什么问题?
解决方案上面的代码没有问题。事实上,你甚至不需要 autoincrement = True
或 db.Sequence('seq_reg_id',start = 1,increment = 1) / code>,因为SQLAlchemy会自动将未标记为FK的第一个 Integer
PK列设置为 autoincrement = True
。
在这里,我已经根据你的设置了一个工作设置。 SQLAlechemy的ORM将负责生成id和填充对象,如果您使用您定义的基于Declarative Base的类来创建对象实例。
from flask import Flask
from flask.ext.sqlalchemy import SQLAlchemy
$ b $ app = Flask(__ name__)
app。调试=真
的app.config [ 'SQLALCHEMY_DATABASE_URI'] = '的PostgreSQL://用户:密码@本地/ TESTDB'
的app.config [ 'SQLALCHEMY_ECHO'] = TRUE
分贝= SQLAlchemy的(app)
class Region(db.Model):
__tablename__ ='regions'
id = db.Column(db.Integer,primary_key = True)
name = db.Column(db.String(100))
db.drop_all()
db.create_all()
region = Region(name = Over the Thar')
app.logger.info(region.id)#目前无,持续之前
db.session.add(region)
db.session.commit ()
app.logger.info(region.id)#被赋予一个id后为1
$ b region2 = Region(name ='Yet Another Up Yar')
db.session.add(region2)
db.session.commit()
app .logger.info(region2.id)#和2
if __name__ =='__main__':
app.run(port = 9001)
I want my model's primary key to be an autoincrementing integer. Here is how my model looks like
class Region(db.Model):
__tablename__ = 'regions'
id = db.Column(db.Integer, primary_key=True, autoincrement=True)
name = db.Column(db.String(100))
parent_id = db.Column(db.Integer, db.ForeignKey('regions.id'))
parent = db.relationship('Region', remote_side=id, primaryjoin=('Region.parent_id==Region.id'), backref='sub-regions')
created_at = db.Column(db.DateTime, default=db.func.now())
deleted_at = db.Column(db.DateTime)
The above code creates my table but does not make id
autoincrementing. So if in my insert query I miss the id
field it gives me this error
ERROR: null value in column "id" violates not-null constraint
So I changed the id
declaration to look like this
id = db.Column(db.Integer, db.Sequence('seq_reg_id', start=1, increment=1),
primary_key=True)
Still the same error. What is wrong with the code above?
解决方案 Nothing is wrong with the above code. In fact, you don't even need autoincrement=True
or db.Sequence('seq_reg_id', start=1, increment=1),
as SQLAlchemy will automatically set the first Integer
PK column that's not marked as a FK as autoincrement=True
.
Here, I've put together a working setup based on yours. SQLAlechemy's ORM will take care of generating id's and populating objects with them if you use the Declarative Base based class that you've defined to create instances of your object.
from flask import Flask
from flask.ext.sqlalchemy import SQLAlchemy
app = Flask(__name__)
app.debug = True
app.config['SQLALCHEMY_DATABASE_URI'] = 'postgresql://user:password@localhost/testdb'
app.config['SQLALCHEMY_ECHO'] = True
db = SQLAlchemy(app)
class Region(db.Model):
__tablename__ = 'regions'
id = db.Column(db.Integer, primary_key=True)
name = db.Column(db.String(100))
db.drop_all()
db.create_all()
region = Region(name='Over Yonder Thar')
app.logger.info(region.id) # currently None, before persistence
db.session.add(region)
db.session.commit()
app.logger.info(region.id) # gets assigned an id of 1 after being persisted
region2 = Region(name='Yet Another Up Yar')
db.session.add(region2)
db.session.commit()
app.logger.info(region2.id) # and 2
if __name__ == '__main__':
app.run(port=9001)
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