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From Riyafa Abdul Hameed <riy...@apache.org>
Subject Re: Creating aggregate functions
Date Wed, 19 Jul 2017 14:55:24 GMT
Hi again,

Any suggestions on this? Or anyone I can reach to who are not on this list
or not active on the list?

Thank you.

On 17 July 2017 at 17:18, Riyafa Abdul Hameed <riyafa@apache.org> wrote:

> Hi again,
>
> I think I can understand how to write the descriptor in the packages:
> org.apache.asterix.runtime.aggregates.std and  org.apache.asterix.runtime.aggregates.scalar.
> But I am not sure I understand how to write the descriptor in the package:
> org.apache.asterix.runtime.aggregates.serializable.std  because it
> requires setting a state in the init function that doesn't seem to have a
> pattern in the other descriptors.
> Also I don't seem to understand the reasons for implementing each of these
> descriptors for the aggregate functions.
>
> On 17 July 2017 at 16:56, Riyafa Abdul Hameed <riyafa.12@cse.mrt.ac.lk>
> wrote:
>
>> Hi all,
>>
>> I meant any explanation on the implementation of aggregate functions in
>> AsterixDB would be highly appreciated.
>>
>> Thank you.
>> Yours sincerely,
>> Riyafa
>>
>> On 16 July 2017 at 08:01, Riyafa Abdul Hameed <riyafa@apache.org> wrote:
>>
>>> Dear all,
>>>
>>> I am trying to create aggregate functions and I see there are more than
>>> one function descriptors for one single function.
>>> For example the function array_count(collection) has the following
>>> descriptors:
>>>
>>>
>>>    - ScalarCountAggregateDescriptor
>>>    - SerializableCountAggregateDescriptor
>>>    - CountAggregateDescriptor
>>>
>>> I am not sure I understand the difference between each of this. Can you
>>> please provide and example or point me to a documentation entry to learn
>>> how to properly implement aggregate functions?
>>>
>>> The function I am trying to implement is ST_Extent.
>>> <https://postgis.net/docs/manual-1.4/ST_Extent.html>
>>>
>>> Thank you.
>>>
>>> Yours sincerely,
>>>
>>> Riyafa
>>>
>>
>>
>>
>> --
>> Riyafa Abdul Hameed
>> Undergraduate, University of Moratuwa
>>
>> Email: riyafa.12@cse.mrt.ac.lk
>> Website: https://riyafa.wordpress.com/ <http://riyafa.wordpress.com/>
>> <http://facebook.com/riyafa.ahf>  <http://lk.linkedin.com/in/riyafa>
>> <http://twitter.com/Riyafa1>
>>
>
>

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