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Hive >> mail # dev >> Custom UserDefinedFunction in Hive


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Re: Custom UserDefinedFunction in Hive
Hi Jan,
I figured that out, it is working fine for me now. The only question I have
is, if I am doing like this-

SELECT * FROM REALTIME where dt= yesterdaydate('yyyyMMdd') LIMIT 10;

Then the above query will be evaluated as below right?

SELECT * FROM REALTIME where dt= ‘20120806’ LIMIT 10;

So that means it will look for data in the corresponding dt partition
*(20120806)
*only right as above table is partitioned on dt column ? And it will not
scan the whole table right?**

*Raihan Jamal*

On Mon, Aug 6, 2012 at 10:56 PM, Jan Dolinár <[EMAIL PROTECTED]> wrote:

> Hi Jamal,
>
> Check if the function really returns what it should and that your data are
> really in yyyyMMdd format. You can do this by simple query like this:
>
> SELECT dt, yesterdaydate('yyyyMMdd') FROM REALTIME LIMIT 1;
>
> I don't see anything wrong with the function itself, it works well for me
> (although I tested it in hive 0.7.1). The only thing I would change about
> it would be to optimize it by calling 'new' only at the time of
> construction and reusing the object when the function is called, but that
> should not affect the functionality at all.
>
> Best regards,
> Jan
>
>
>
>
> On Tue, Aug 7, 2012 at 3:39 AM, Raihan Jamal <[EMAIL PROTECTED]>wrote:
>
>> *Problem*
>>
>> I created the below UserDefinedFunction to get the yesterday's day in the
>> format I wanted as I will be passing the format into this below method from
>> the query.
>>
>>
>>
>> *public final class YesterdayDate extends UDF {*
>>
>> * *
>>
>> *                public String evaluate(final String format) { *
>>
>> *                                DateFormat dateFormat = new
>> SimpleDateFormat(format); *
>>
>> *                                Calendar cal = Calendar.getInstance();*
>>
>> *                                cal.add(Calendar.DATE, -1);     *
>>
>> *                                return
>> dateFormat.format(cal.getTime()).toString(); *
>>
>> *                } *
>>
>> *}*
>>
>>
>>
>>
>>
>> So whenever I try to run the query like below by adding the jar to
>> classpath and creating the temporary function yesterdaydate, I always get
>> zero result back-
>>
>>
>>
>> hive> create temporary function *yesterdaydate* as
>> 'com.example.hive.udf.YesterdayDate';
>>
>> OK
>>
>> Time taken: 0.512 seconds
>>
>>
>>
>> Below is the query I am running-
>>
>>
>>
>> *hive> SELECT * FROM REALTIME where dt= yesterdaydate('yyyyMMdd') LIMIT
>> 10;*
>>
>> *OK*
>>
>> * *
>>
>> And I always get zero result back but the data is there in that table for
>> Aug 5th.**
>>
>>
>>
>> What wrong I am doing? Any suggestions will be appreciated.
>>
>>
>>
>>
>>
>> NOTE:- As I am working with Hive 0.6 so it doesn’t support variable
>> substitution thing, so I cannot use hiveconf here and the above table has
>> been partitioned on dt(date) column.**
>>
>
>