Doris学习笔记-Java自定义UDAF

项目最近需要做一些数据统计方面的东西，发现数据字段都是很长一串数字的字符串，Doris自带的函数无法对其进行相应的运算操作，需要扩展实现相关的操作运算。

主要参考官方的文档资料完成相关的自定义扩展。需要注意的是在使用Java代码编写UDAF时，有一些必须实现的函数(标记required)和一个内部类State。

• SUM求和运算函数

public class Sum {
   

    //Need an inner class to store data
    /*required*/
    public static class State {
   
        /*some variables if you need */
        public BigDecimal sum;
    }

    /*required*/
    public State create() {
   
        /* here could do some init work if needed */
        State state = new State();
        state.sum = new BigDecimal(0);
        return state;
    }

    /*required*/
    public void destroy(State state) {
   
        /* here could do some destroy work if needed */
    }

    /*Not Required*/
    public void reset(State state) {
   
        /*if you want this udaf function can work with window function.*/
        /*Must impl this, it will be reset to init state after calculate every window frame*/
        /**
        state.sum = new BigDecimal(0);
        **/
    }

    /*required*/
    //first argument is State, then other types your input
    public void add(State state, String value) throws Exception {
   
        try {
   
            /* here doing update work when input data*/
            if (null != value && !"".equals(value)) {
   
                state.sum = state.sum.add(new BigDecimal(value));
            }
        } catch (Exception e) {
   
            log.info(e.getMessage());
        }
    }

    /*required*/
    public void serialize(State state, DataOutputStream out)  {
   
        /* serialize some data into buffer */
        try {
   
            out.writeUTF(state.sum.toString());
        } catch (Exception e) {
   
            /* Do not throw exceptions */
            log.info(e.getMessage());
        }
    }

    /*required*/
    public void deserialize(State state, DataInputStream in)  {
   
        /* deserialize get data from buffer before you put */
        String value = "0";
        try {
   
            value = in.readUTF();
        } catch (Exception e) {
   
            /* Do not throw exceptions */
            log.info(e.getMessage());
        }
        state.sum = new BigDecimal(value);
    }

    /*required*/