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Hive, mail # user - Hive UDAF extending UDAF class: iterate or evaluate method


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Re: Hive UDAF extending UDAF class: iterate or evaluate method
Sanjay Subramanian 2013-08-05, 18:45
Hi Ritesh

To help u get started , I am writing a simple HelloWorld-ish UDF that might help…If it doesn't please ask for more clarifications...

Good Luck
Thanks

sanjay

********************************************************************************
ToUpperCase.java
package com.sanjaysubramanian.utils.hive.udf;
import org.apache.hadoop.hive.ql.exec.UDF;
public final class ToUpperCase extends UDF{

    protected final Log logger = LogFactory.getLog(toUpperCase.class);
public String evaluate(final String inputString) {

     if (inputString != null){

return inputString.toUpper;

             }

             else {

return inputString;

    }

       }

}

********************************************************************************

Usage in a Hive script

hive -e "

create temporary function toupper  as 'com.sanjaysubramanian.utils.hive.udf.ToUpperCase';

SELECT
      first_name,
      toupper(first_name)
FROM
      company_names
"

***********************************************************************************

From: Ritesh Agrawal <[EMAIL PROTECTED]<mailto:[EMAIL PROTECTED]>>
Reply-To: "[EMAIL PROTECTED]<mailto:[EMAIL PROTECTED]>" <[EMAIL PROTECTED]<mailto:[EMAIL PROTECTED]>>
Date: Monday, August 5, 2013 9:41 AM
To: "[EMAIL PROTECTED]<mailto:[EMAIL PROTECTED]>" <[EMAIL PROTECTED]<mailto:[EMAIL PROTECTED]>>
Subject: Re: Hive UDAF extending UDAF class: iterate or evaluate method

Hi Lefty,

I used the wiki you sent to write my first version of UDAF. However, I found it to be utterly complex, especially for storing partial results as I am not very familiar with hive API. Then I found another example of UDAF in the hadoop the definitive guide book and it had much simpler code but using different method. Instead of using iterate it was using evaluate method and so I am getting confused.

Ritesh
On Sun, Aug 4, 2013 at 2:18 PM, Lefty Leverenz <[EMAIL PROTECTED]<mailto:[EMAIL PROTECTED]>> wrote:
You might find this wikidoc useful:  GenericUDAFCaseStudy<https://cwiki.apache.org/confluence/display/Hive/GenericUDAFCaseStudy>.

The O'Reilly book "Programming Hive" also has a section called "User-Defined Aggregate Functions" in chapter 13 (Functions), pages 172 to 176.

-- Lefty
On Sun, Aug 4, 2013 at 7:12 AM, Ritesh Agrawal <[EMAIL PROTECTED]<mailto:[EMAIL PROTECTED]>> wrote:
Hi all,

I am trying to write a UDAF function. I found an example that shows how to implement a UDAF in "Hadoop The Definitive Guide" book. However I am little confused. In the book, the author extends UDAF class and implements init, iterate, terminatePartial,  merge and terminate function. However looking at the hive docs (http://hive.apache.org/docs/r0.11.0/api/org/apache/hadoop/hive/ql/exec/UDAF.html), it seems I need to implement init, aggregate, evaluatePartial, aggregatePartial and evaluate function. Please let me know what are the write functions to implement.

Ritesh

--
Lefty
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