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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