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From Kathiresan S <kathiresanselva...@gmail.com>
Subject Re: UDF - Access Tuple Column Values By Name
Date Wed, 06 May 2015 13:14:19 GMT
Hi Jaime,

In my case, the number of arguments passed to the custom function will be
different in different scenarios. I think UDF is designed to take fixed
number of arguments, i believe (also, I see number of arguments column in
SYSTEM.FUNCTION table).

Another question - As we have the row (tuple) at this point of the code
(evaluate method) with all the values in it, why can't we pass the
expression list to the evaluate method from
PhoenixResultSet(RowProjector->columnProjectors), so we could access any
column we want from the tuple? Am i missing something?

Thanks,
Kathir

On Wed, May 6, 2015 at 8:43 AM, Jaime Solano <jdjsolano@gmail.com> wrote:

> Hi Kathir,
>
> I don't know if that's posible, but seems like the better approach is to
> just define your function to take two arguments.
>
> What do you think?
>
> Best,
> -Jaime
> On May 6, 2015 7:50 AM, "Kathiresan S" <kathiresanselvaraj@gmail.com>
> wrote:
>
>> Hi,
>>
>> In UDF, in the implemented evaluate(tuple,ptr) method, i could access the
>> expression object of the columns passed to the UDF, by invoking
>> *getChildren.get(index)*. and then by invoking
>> expression.evaluate(tuple,ptr), i can get the value copied to the ptr
>> object. But, how do i access other elements of the tuple by passing its
>> column name. I don't have access to the expression object of other columns
>> in the select query within the UDF implementation method. Please suggest
>> what we should do to get the value of other columns from the tuple by
>> passing the column name.
>>
>> For eg.
>>
>> CREATE TABLE TESTTABLE (ID VARCHAR, NAME VARCHAR, PREFIX VARCHAR)
>>
>> CREATE FUNCTION MYFUNCTION(VARCHAR) RETURNS VARCHAR WITH 'com.test.CF'
>> using jar '/tmp/cf.jar'
>>
>> SELECT ID,MYFUNCTION(NAME),PREFIX FROM TESTTABLE
>>
>> MYFUNCTION - is expected to concatenate PREFIX columns value and the NAME
>> columns value in each row.
>>
>> In the evaluate method, as i pass the NAME column as argument to the
>> function, i get the expression object of it by invoking
>> nameExpr=getChildren.get(0) and then by invoking
>> nameExpr.evaluate(tuple,ptr) i can have the value copied to ptr. In this
>> case, is there a way to access the prefix columns value from the tuple, as
>> its also present in the SELECT clause.
>>
>> Thanks,
>> Kathir
>>
>

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