Question

当我尝试运行db.create_all()来创建MySQL表时，我收到以下错误：

sqlalchemy.exc.InternalError: (pymysql.err.InternalError) (1071, 'Specified key was too long; max key length is 767 bytes') [SQL: '\nCREATE TABLE post (\n\tid INTEGER NOT NULL AUTO_INCREMENT, \n\tblog_id INTEGER, \n\tuser_id INTEGER, \n\ttitle VARCHAR(80), \n\tbody TEXT, \n\timage VARCHAR(255), \n\tslug VARCHAR(256), \n\tpublish_date DATETIME, \n\tlive BOOL, \n\ttag_id INTEGER, \n\tPRIMARY KEY (id), \n\tFOREIGN KEY(blog_id) REFERENCES blog (id), \n\tFOREIGN KEY(user_id) REFERENCES user (id), \n\tUNIQUE (slug), \n\tCHECK (live IN (0, 1)), \n\tFOREIGN KEY(tag_id) REFERENCES tag (id)\n)\n\n']

如何解决此错误？我不确定问题的根源。我可以在我的开发环境中create_all()数据库，但不能在我的主机上。我认为它是服务器MySQL服务的列大小限制。我是否无效地编码表格内容？我是否错误地构建了模型？我试图更改settings.py：

DB_URI = "mysql+pymysql://%s:%s@%s/%s?charset=utf8" % (DB_USERNAME, DB_PASSWORD, DB_HOST, BLOG_DATABASE_NAME)

我还尝试SET @@global.innodb_large_prefix = 1;作为this question suggested。

模型

from my_app import db, uploaded_images
from datetime import datetime

class Blog(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(80))
    admin = db.Column(db.Integer, db.ForeignKey('user.id'))
    posts = db.relationship('Post', backref='blog', lazy='dynamic')

    def __init__(self, name, admin):
        self.name = name
        self.admin = admin

    def __repr__(self):
        return '<Name %r>' % self.name

class Post(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    blog_id = db.Column(db.Integer, db.ForeignKey('blog.id'))
    user_id = db.Column(db.Integer, db.ForeignKey('user.id'))
    title = db.Column(db.String(80))
    body = db.Column(db.Text)
    image = db.Column(db.String(255))
    slug = db.Column(db.String(256), unique=True)
    publish_date = db.Column(db.DateTime)
    live = db.Column(db.Boolean)

    tag_id = db.Column(db.Integer, db.ForeignKey('tag.id'))
    tag = db.relationship('Tag',
        backref=db.backref('posts', lazy='dynamic'))

    @property
    def imgsrc(self):
        return uploaded_images.url(self.image)

    def __init__(self, blog, user, title, body, tag, image=None, slug=None, publish_date=None, live=True):
            self.blog_id = blog.id
            self.user_id = user.id
            self.title = title
            self.body = body
            self.tag = tag
            self.image = image
            self.slug = slug
            if publish_date is None:
                self.publish_date = datetime.utcnow()
            self.live = live

    def __repr__(self):
        return '<Post %r>' % self.title


class Tag(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(50))

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

    def __repr__(self):
        return self.name

from my_app import db
from blog.models import Post
from datetime import datetime
import datetime


class User(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    fullname = db.Column(db.String(80))
    email = db.Column(db.String(35), unique=True)
    username = db.Column(db.String(25), unique=True)
    password = db.Column(db.String(60))
    paid_until = db.Column(db.DateTime, default=datetime.datetime.utcnow)

    posts = db.relationship('Post', backref='user', lazy='dynamic')

    def __init__(self, fullname, email, username, password):
        self.fullname = fullname
        self.email = email
        self.username = username
        self.password = password

    def __repr__(self):
        return '<User %r>' % self.username

谢谢。

Answer 1

嗯，这个实际上是由学生在课程中回答的。问题是slug上的索引（当您将其标记为UNIQUE时，它正在创建索引）。

因为它是一个varchar，MySQL中索引列的最大字符串长度是255.如果slug是utf8，那么我们需要假设更长的长度（255/3 =最多85个字符，因为每个utf8字符是3个字节）。

所以只需将slug上的varchar大小减少到少于256个字符（学生提到252个工作）。

这是问题的Stack Overflow discussion。

不能create_all Flask-SQLAlchemy - 指定的密钥太长了

模型

1 个答案: