Detailed process of UDF implementation in hive

Source: Internet
Author: User

Hive udfs are similar to user-defined functions such as MySQL.

However, it needs to be written in Java instead of using traditional SQL.

To implement a UDF, follow these steps:

  1. Implement a Java class that inherits from UDF
  2. Compress the jar package and add it to the hive classpath.
  3. Generate a user-defined function and execute select
  4. Delete the temporary function just created

The UDF below is a function I added to the hive array.

Used to determine whether an array contains a value. This function is not available in hive standard functions.

package;import java.util.*;import org.apache.hadoop.hive.ql.exec.UDF;import;import;import; public final class ArrayContains extends UDF {   public BooleanWritable evaluate(ArrayList<String> arr,Text ele)    {        BooleanWritable rtn = new BooleanWritable(false);        if (arr == null || arr.size() < 1)        {            return rtn;        }        try {            String cstr = ele.toString();               for (String str : arr)            {                if (str.equals(cstr))                {                    rtn = new BooleanWritable(true);                    break;                }            }         } catch (Exception e) {            e.printStackTrace();        }         return rtn;    }}

Then execute the compilation and packaging:

Javac-classpath/opt/hadoop_client/hadoop/hadoop-0.20.2 + 228-core.jar:/opt/hadoop_client/hive/lib/hive-exec-0.5.0.jar src/COM/Sohu/hadoop/hive/UDF/arraycontains. java-d build
Jar-cvf hadooop-mc-udf.jar-C build.

Finally, execute the hive QL query:

Hive-e "add JAR/opt/fe-/ UDF/hadooop-mc-udf.jar; drop temporary function array_contains; create temporary function array_contains as 'com. sohu. hadoop. hive. UDF. arraycontains '; select SUV, channelid from pvlog_pre where array_contains (channelid, '2 ')"

Contact Us

The content source of this page is from Internet, which doesn't represent Alibaba Cloud's opinion; products and services mentioned on that page don't have any relationship with Alibaba Cloud. If the content of the page makes you feel confusing, please write us an email, we will handle the problem within 5 days after receiving your email.

If you find any instances of plagiarism from the community, please send an email to: and provide relevant evidence. A staff member will contact you within 5 working days.

A Free Trial That Lets You Build Big!

Start building with 50+ products and up to 12 months usage for Elastic Compute Service

  • Sales Support

    1 on 1 presale consultation

  • After-Sales Support

    24/7 Technical Support 6 Free Tickets per Quarter Faster Response

  • Alibaba Cloud offers highly flexible support services tailored to meet your exact needs.