如何在 sqlalchemy 中应用自定义过滤器?我试过@hybrid_property 和@hybrid_method。但是,他们给出了错误。这是我的代码:
class Product(db.Model):
__tablename__ = 'products'
id = db.Column(db.Integer, primary_key=True)
owner_id = db.Column(db.Integer, db.ForeignKey('users.id'), nullable=False)
keywords = db.Column(db.String(64)) # keywords for ease of browsing
details = db.Column(db.Text)
removed = db.Column(db.Boolean, default=False)
@hybrid_method
def toKeywordLevenshteinDistance(self, keywords):
"""
:param user input product keywords
:return Levenshtein(user_input_keywords, product_keywords)
"""
return fuzz.partial_ratio(self.keywords, keywords)
@toKeywordLevenshteinDistance.expression
def toKeywordLevenshteinDistance(cls, keywords):
return func.fuzz.partial_ratio(cls.keywords, keywords)
>>> p=similarProducts('jrjk')
这是输出:
File "C:\Users\AllWatt\App\flask\myStoreEnv\lib\site-packages\sqlalchemy\engine\default.py",
line 608, in do_execute
cursor.execute(statement, parameters)
sqlalchemy.exc.OperationalError: (sqlite3.OperationalError) no such function: levenshtein
[SQL: SELECT products.id AS products_id, products.owner_id AS products_owner_id,
products.keywords AS products_keywords, products.details AS products_details,
products.removed AS products_removed, products."when" AS products_when FROM products
WHERE levenshtein(products.keywords, ?) > ?] [parameters: ('jrjk', 20)]
(Background on this error at: http://sqlalche.me/e/13/e3q8)
您可以使用事件侦听器在连接时向 sqlite 注册自定义函数。这是一个简单的例子:
from flask import Flask
from flask_sqlalchemy import SQLAlchemy
import sqlalchemy as sa
app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite://'
db = SQLAlchemy(app)
def doubleit(word):
return word * 2
@sa.event.listens_for(db.engine, 'connect')
def on_connect(dbapi_connection, connection_record):
dbapi_connection.create_function('doubleit', 1, doubleit)
@app.route('/<word>')
def word_doubler(word):
result = db.session.query(sa.func.doubleit(word))
return result.scalar()
if __name__ == '__main__':
app.run(debug=True)
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