Doris学习笔记-Java自定义UDAF-Toy模板网

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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*/
    public void merge(State state, State rhs) throws Exception {
        /* merge data from state */
        if (null == rhs || null == rhs.sum || null == state) {
            return;
        }
        try {
            BigDecimal sum = state.sum;
            if (null == sum) {
                sum = new BigDecimal(0);
            }
            state.sum = sum.add(rhs.sum);
        } catch (Exception e) {
            log.info(e.getMessage());
        }
    }

    /*required*/
    //return Type you defined
    public String getValue(State state) throws Exception {
        /* return finally result */
        return null == state || null == state.sum ? "0" : state.sum.toString();
    }

}

AVG平均数运算函数

public class Avg {

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

    /*required*/
    public State create() {
        /* here could do some init work if needed */
        State state = new State();
        state.sum = new BigDecimal(0);
        state.count = 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));
                state.count += 1;
            }
        } 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());
            out.writeInt(state.count);
        } 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";
        Integer count = 0;
        try {
            value = in.readUTF();
            count = in.readInt();
        } catch (Exception e) {
            /* Do not throw exceptions */
            log.info(e.getMessage());
        }
        state.sum = new BigDecimal(value);
        state.count = count;
    }

    /*required*/
    public void merge(State state, State rhs) throws Exception {
        /* merge data from state */
        if (null == rhs || null == rhs.sum || null == state) {
            return;
        }
        try {
            BigDecimal sum = state.sum;
            sum = null == sum ? new BigDecimal(0) : sum;
            state.sum = sum.add(rhs.sum);
            Integer count = state.count;
            count = null == count ? 0 : count;
            state.count = count + rhs.count;
        } catch (Exception e) {
            log.info(e.getMessage());
        }
    }

    /*required*/
    //return Type you defined
    public String getValue(State state) throws Exception {
        /* return finally result */
        return null == state || null == state.sum || null == state.count ? "0" :
            state.sum.divide(new BigDecimal(state.count)).toString();
    }

}

MAX最大值运算函数

public class Max {

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

    /*required*/
    public State create() {
        /* here could do some init work if needed */
        State state = new State();
        state.max = 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)) {
                BigDecimal valueBd = new BigDecimal(value);
                state.max = state.max.compareTo(valueBd) == -1 ? valueBd : state.max;
            }
        } catch (Exception e) {
            log.info(e.getMessage());
        }
    }

    /*required*/
    public void serialize(State state, DataOutputStream out)  {
        /* serialize some data into buffer */
        try {
            out.writeUTF(state.max.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.max = new BigDecimal(value);
    }

    /*required*/
    public void merge(State state, State rhs) throws Exception {
        /* merge data from state */
        if (null == rhs || null == rhs.max || null == state) {
            return;
        }
        try {
            BigDecimal sum = state.max;
            if (null == sum) {
                sum = new BigDecimal(0);
            }
            state.max = state.max.compareTo(rhs.max) == -1 ? rhs.max : state.max;
        } catch (Exception e) {
            log.info(e.getMessage());
        }
    }

    /*required*/
    //return Type you defined
    public String getValue(State state) throws Exception {
        /* return finally result */
        return null == state || null == state.max ? "0" : state.max.toString();
    }

}

项目打成jar包，上传至每个FE、BE节点。
创建函数命令

CREATE FUNCTION 
name ([,...])
[RETURNS] rettype
PROPERTIES (["key"="value"][,...])  

CREATE AGGREGATE FUNCTION
name ([,...])
[RETURNS] rettype
PROPERTIES (["key"="value"][,...])

PROPERTIES中symbol表示的是包含UDF类的类名，这个参数是必须设定的。
PROPERTIES中file表示的包含用户UDF的jar包，这个参数是必须设定的。
PROPERTIES中type表示的 UDF 调用类型，默认为 Native，使用 Java UDF时传 JAVA_UDF。
PROPERTIES中always_nullable表示的 UDF 返回结果中是否有可能出现NULL值，是可选参数，默认值为true。
name: 一个function是要归属于某个DB的，name的形式为dbName.funcName。当dbName没有明确指定的时候，就是使用当前session所在的db作为dbName。

CREATE GLOBAL AGGREGATE FUNCTION udaf_sum(string) RETURNS string PROPERTIES (
"file"="file:///home/doris/udf/doris-udaf-1.0.0.jar",
"symbol"="com.doris.udaf.func.Sum",
"always_nullable"="true",
"type"="JAVA_UDF"
);

"file"="http://ip:port/xxxxxx.jar", 当在多机环境时也可以使用http的方式下载jar包。必须让每个BE节点都能获取到jar包; 否则将会返回错误状态信息"Couldn't open file ......"。
"always_nullable"可选属性, 如果在计算中对出现的NULL值有特殊处理，确定结果中不会返回NULL，可以设为false，这样在整个查询计算过程中性能可能更好些。

DROP GLOBAL FUNCTION udaf_sum(string);

SHOW CREATE FUNCTION udaf_sum(string);

官方提供的使用须知
1、不支持复杂数据类型（HLL，Bitmap）。
2、当前允许用户自己指定JVM最大堆大小，配置项是jvm_max_heap_size。配置项在BE安装目录下的be.conf全局配置中，默认512M，如果需要聚合数据，建议调大一些，增加性能，减少内存溢出风险。
3、char类型的udf在create function时需要使用String类型。
4、由于jvm加载同名类的问题，不要同时使用多个同名类作为udf实现，如果想更新某个同名类的udf，需要重启be重新加载classpath。
官方还提供远程UDAF的文档资料，有需求的话可以参考示例。
还有一点就是发现自定义的UDAF无法在物料视图里面使用。

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