Question

我已经尝试了sqlalchemy create tables中提到的解决方案，并且还提到了烧瓶文档http://flask-sqlalchemy.pocoo.org/2.1/contexts/。我在使用create_all（）创建数据库表时遇到问题。这是我的代码。

>>> from flask import Flask
>>> app = Flask('myflaskapp')
>>> from flask_sqlalchemy import SQLAlchemy
>>> app.url_map.strict_slashes = False
>>> app.config['SQLALCHEMY_DATABASE_URI'] = 'postgresql+psycopg2://my_dbuser:my_dbuser_password@localhost/my_dev_db'
>>> app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
>>> from myflaskapp.models import AdRequest, AdResult
>>> AdRequest.__table__
Table('ad_request', MetaData(bind=None), Column('id', Integer(), table=<ad_request>, primary_key=True, nullable=False), Column('status', String(length=10), table=<ad_request>, default=ColumnDefault('NEW')), Column('status_msg', String(length=100), table=<ad_request>, default=ColumnDefault('')), Column('query_str', String(length=100), table=<ad_request>), schema=None)
>>> db = SQLAlchemy(app)
>>> db.engine
Engine(postgresql+psycopg2://my_dbuser:***@localhost/my_dev_db)
>>> db.metadata.create_all(db.engine)
>>> db.engine
Engine(postgresql+psycopg2://my_dbuser:***@localhost/my_dev_db)
>>> db
<SQLAlchemy engine=postgresql+psycopg2://my_dbuser:***@localhost/my_dev_db>
>>> db.session.commit()

在postgres控制台上，“\ dt”不会列出因运行create_all而应创建的新表ad_request。

此外，我添加了调试，如下app ['SQLALCHEMY_ECHO'] = True，我得到以下输出，我无法破译。

>>> app.config['SQLALCHEMY_ECHO']=True
>>> from models import *
>>> with app.app_context():
...   db.create_all()
... 
2017-07-17 10:24:09,766 INFO sqlalchemy.engine.base.Engine select relname from pg_class c join pg_namespace n on n.oid=c.relnamespace where pg_catalog.pg_table_is_visible(c.oid) and relname=%(name)s
2017-07-17 10:24:09,766 INFO sqlalchemy.engine.base.Engine {'name': 'ad_request'}
2017-07-17 10:24:09,768 INFO sqlalchemy.engine.base.Engine select relname from pg_class c join pg_namespace n on n.oid=c.relnamespace where pg_catalog.pg_table_is_visible(c.oid) and relname=%(name)s
2017-07-17 10:24:09,769 INFO sqlalchemy.engine.base.Engine {'name': 'ad_result'}
2017-07-17 10:24:09,772 INFO sqlalchemy.engine.base.Engine 
CREATE TABLE ad_request (
    id SERIAL NOT NULL, 
    status VARCHAR(10), 
    status_msg VARCHAR(100), 
    query_str VARCHAR(100), 
    PRIMARY KEY (id)
)
2017-07-17 10:24:09,772 INFO sqlalchemy.engine.base.Engine {}
2017-07-17 10:24:09,779 INFO sqlalchemy.engine.base.Engine COMMIT
2017-07-17 10:24:09,780 INFO sqlalchemy.engine.base.Engine 
CREATE TABLE ad_result (
    id SERIAL NOT NULL, 
    uuid_s VARCHAR(50), 
    score FLOAT, 
    ad_request_id INTEGER, 
    PRIMARY KEY (id), 
    FOREIGN KEY(ad_request_id) REFERENCES ad_request (id)
)
2017-07-17 10:24:09,780 INFO sqlalchemy.engine.base.Engine {}
2017-07-17 10:24:09,784 INFO sqlalchemy.engine.base.Engine COMMIT

我注意到AdRequest。表显示表格（'ad_request'，MetaData（bind =无），... 如何将AdRequest绑定到db.metadata？以下是我的models.py

# models.py
from flask_sqlalchemy import SQLAlchemy
from flask_marshmallow import Marshmallow


db = SQLAlchemy()
ma = Marshmallow()


class AdRequest(db.Model):
    id = db.Column(db.Integer, primary_key=True, autoincrement=True)
    status = db.Column(db.String(10), default="NEW")
    status_msg = db.Column(db.String(100), default="")
    query_str = db.Column(db.String(100))

    def __init__(self, query_str):
        self.query_str = query_str

    def __repr__(self):
        return '<AdRequest %r, %r, %r, %r>' % (self.id, self.query_str, self.status, self.status_msg)

    def as_dict(self):
        return {'id': self.id,
                'query_str': self.query_str,
                'status': self.status,
                'status_msg': self.status_msg,
                }


class AdResult(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    uuid_s = db.Column(db.String(50))
    score = db.Column(db.Float)
    ad_request_id = db.Column(db.Integer, db.ForeignKey('ad_request.id'))

    def __init__(self, uuid_s, score, ad_request_id):
        self.uuid_s = uuid_s
        self.score = score
        self.ad_request_id = ad_request_id

    def __repr__(self):
        return '<AdResult %r, %r, %s>' % (self.id, self.uuid_s, self.ad_request_id)


class AdRequestSchema(ma.Schema):
    class Meta:
        # Fields to expose
        fields = ('id', 'status', 'status_msg', 'query_str')

Answer 1

对于SQLAlchemy来说，顺序很重要。在声明模型和使用它们时，必须使用相同的SQLAlchemy实例。在您提供的示例中，您创建了两次数据库 - 一次在模型文件中，一次在Python控制台中。

只需创建一个名为 database.py 的单独文件，其中包含两行：

from flask_sqlalchemy import SQLAlchemy
db = SQLAlchemy()

然后在您的模型中导入它并将其用作模型的基础：

from database import db

class AdRequest(db.Model):
    id = db.Column(db.Integer, primary_key=True, autoincrement=True)

# rest of your models file

使用以下命令创建您的应用：

from flask import Flask
from database import db
from models import AdRequest, AdResult

app = Flask('myflaskapp')
app.url_map.strict_slashes = False

app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///test.db'
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False

with app.app_context():
    db.init_app(app)    # this is important!
    db.create_all()

如果有帮助，请告诉我。

编辑：您可以通过运行它来检查我的代码是否有效，并检查是否创建了test.db文件。如果文件存在，但您仍有问题，可能是PostgreSQL特定问题。

sqlalchemy如何将元数据绑定到表

1 个答案: