Hive自定义UDF函数

将科学计数法转成decimal

编写java

package cn.bdp.udf;

import org.apache.hadoop.hive.ql.exec.Description;
import org.apache.hadoop.hive.ql.exec.UDF;
import java.math.BigDecimal;

@Description(name = "number_convert",
        value = "_FUNC_(string) - Convert a string to bigDecimal ，return str.")
public class NumberConvertUDF extends UDF {

    public String evaluate(String str) {
        if (str == null) {
            return "0";
        }
        try {
            BigDecimal bd = new BigDecimal(str);
            String result = bd.toPlainString();
            return result;
        } catch (Exception e) {
            return "0";
        }
    }
}

打包生成my_udf_jar.jar

创建自定义函数

# 将jar包上传到HDFS
hive> add jar /tmp/my_udf_jar.jar;

# 将jar包上传到HDFS
hive> create temporary function number_convert as 'cn.bdp.udf.NumberConvertUDF ';

hive> select number_convert("4.548820080129802E-4");

0.0004548820080129802

hive> select CAST( number_convert("4.548820080129802E-4") AS decimal(9,5) )  ;

0.00045

更新jar包操作

# 列出所有jar
hive> list jars;

# 删除对应的tmp
hive> delete jar /tmp/448a59e7-5ef8-4b76-8eed-ba04c73e126a_resources/udf-1.0.jar;

hive> DROP TEMPORARY FUNCTION number_convert;