text: from flask_sqlalchemy import SQLAlchemy
  from config import HASH_LEN
  
  db = SQLAlchemy()
  
  
  class Url(db.Model):
      __tablename__ = "urls"
  
      hash = db.Column(db.String(HASH_LEN), unique=True, primary_key=True)
      forward_to = db.Column(db.Text(), unique=True, primary_key=True)
      visited_times = db.Column(db.Integer, default=0)
  