如何在FlinkSQL中创建和使用自定义UDAF？

https://www.80wz.com/zb_users/upload/2025/05/20250528094638174839679814848.txt

// 通过TableEnvironment注册（Java代码）
StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
StreamTableEnvironment tableEnv = StreamTableEnvironment.create(env);
// 注册UDAF为临时函数
tableEnv.createTemporarySystemFunction("my_avg", MyAvgFunction.class);

-- 计算用户订单的平均金额
SELECT 
  user_id, 
  my_avg(amount) AS avg_amount 
FROM orders 
GROUP BY user_id;