from flask import Flask
from flask_sqlalchemy import SQLAlchemy, SignallingSession, get_state
from sqlalchemy import orm


class RoutingSession(SignallingSession):
  def get_bind(self, mapper=None, clause=None):
    state = get_state(self.app)

    # 判斷讀寫(xiě)操作
    if self._flushing: # 寫(xiě)操作 ,使用主數(shù)據(jù)庫(kù)
      print("寫(xiě)入數(shù)據(jù)")
      return state.db.get_engine(self.app, bind='master')
    else: # 讀操作, 使用從數(shù)據(jù)庫(kù)
      print('讀取數(shù)據(jù)')
      return state.db.get_engine(self.app, bind='slave')


class RoutingSQLAlchemy(SQLAlchemy):
  def create_session(self, options):
    return orm.sessionmaker(class_=RoutingSession, db=self, **options)


app = Flask(__name__)
# 設(shè)置數(shù)據(jù)庫(kù)的連接地址
app.config['SQLALCHEMY_DATABASE_URI'] = 'mysql://root:mysql@192.168.105.134:3306/demo'
# 設(shè)置數(shù)據(jù)庫(kù)的綁定地址
app.config['SQLALCHEMY_BINDS'] = {
  'master': "mysql://root:mysql@192.168.105.134:3306/demo",
  'slave': "mysql://root:mysql@192.168.105.134:8306/demo"
}
# 設(shè)置是否追蹤數(shù)據(jù)庫(kù)變化  一般不會(huì)開(kāi)啟, 影響性能
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
# 設(shè)置是否打印底層執(zhí)行的SQL語(yǔ)句
app.config['SQLALCHEMY_ECHO'] = False

# 創(chuàng)建數(shù)據(jù)庫(kù)連接對(duì)象
db = RoutingSQLAlchemy(app)

# 用戶表 一
class User(db.Model):
  __tablename__ = 't_user'
  id = db.Column(db.Integer, primary_key=True)
  name = db.Column(db.String(20), unique=True)


@app.route('/')
def index():
  # 增加數(shù)據(jù)
  user1 = User(name='zs')
  db.session.add(user1)
  db.session.commit()

  # 查詢數(shù)據(jù)
  users = User.query.all()
  print(users)
  return "index"

if __name__ == '__main__':
  # 刪除所有繼承自db.Model的表
  db.drop_all()
  # 創(chuàng)建所有繼承自db.Model的表
  db.create_all()
  app.run(debug=True)