在Flask-sqlalchemy和Postgresql中使用JSON Type

Question

背景: 我正在构建一个Flask应用程序,我已将数据存储到postgresql数据库和JSON列类型中.

任务: 在我的视图函数中,我想从JSON列的{Key:Value}订购数据库查询

完成:我已成功通过使用以下命令在psql命令行执行此查询,例如:

select*from target where cast(product - >>'profit'as float)> 100 order by cast(product - >>'salesrank'as integer)asc;

问题:我无法在我的代码中复制此查询(请参阅下面的额外信息部分中的模型代码)

from app import app, db
from models import Target 

data = Target.query.order_by(Target.product['salesrank'])

收到错误 - ProgrammingError:(ProgrammingError)无法识别类型json的排序运算符LINE 2:FROM target ORDER BY target.product - >'salesrank'^ HINT:使用显式排序运算符或修改查询.'SELECT target.id AS target_id,target.store AS target_store,target.product AS target_product,target.asin AS target_asin,target.date AS target_date \nFROM target ORDER BY target.product - >%(product_1)s \n LIMIT% (param_1)s'{'product_1':'salesrank','param_1':1}

额外信息 我的目标模型设置如下:

#models.py
from app import db
from sqlalchemy.dialects.postgresql import JSON
import datetime

class Target(db.Model):
    __tablename__ = 'target'

    id = db.Column(db.Integer)
    store = db.Column(db.String())
    product = db.Column(JSON)
    asin = db.Column(db.String(), primary_key=True)
    date = db.Column(db.DateTime, default=datetime.datetime.utcnow())

我的App.py文件,我定义了Flask和Sqlalchemy

from flask import Flask
import os
from flask.ext.sqlalchemy import SQLAlchemy
from flask_bootstrap import Bootstrap

app = Flask(__name__)
app.config.from_object(os.environ['APP_SETTINGS'])
db = SQLAlchemy(app)
Bootstrap(app)

import views
from app import app
from models import Result

if __name__ == '__main__':
    app.run(host='192.168.1.5', port=5000, debug=True)

感谢您提供任何帮助!

Answer 1

查看SQLAchemy文档中的JSON数据类型,看起来您应该能够使用该.cast方法:

from sqlalchemy.types import Integer

from app import app, db
from models import Target 

# SQLAlchemy 1.1+
data = Target.query.order_by(Target.product['salesrank'].astext.cast(Integer))

# SQLAlchemy < 1
data = Target.query.order_by(Target.product['salesrank'].cast(Integer))