From: | Atri Sharma <atri(dot)jiit(at)gmail(dot)com> |
---|---|
To: | Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> |
Cc: | Vik Fearing <vik(dot)fearing(at)dalibo(dot)com>, PG Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: median and percentile function implementation |
Date: | 2013-08-26 16:50:56 |
Message-ID: | CAOeZVicY7vVHHcnqHfe2KwLzFcVgXO_84oebcx7et-QAG5goDA@mail.gmail.com |
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Lists: | pgsql-hackers |
On Mon, Aug 26, 2013 at 10:15 PM, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> wrote:
> Hello
>
> very nice! I tested it and works very well.
>
> And I looking for implementation in core.
>
> Two notes:
>
> * should to support string_agg and array_agg
>
> Regards
>
> Pavel
>
>
>
> 2013/8/26 Vik Fearing <vik(dot)fearing(at)dalibo(dot)com>
>>
>> On 08/26/2013 02:39 PM, Pavel Stehule wrote:
>> > Hello
>> >
>> > Three years ago we worked on implementation of median function.
>> >
>> >
>> > http://www.postgresql.org/message-id/AANLkTimRksUOgGsK7-gTXnvJJGL-1QvuqxidusZQwep6@mail.gmail.com
>> >
>> >
>> > Can we implement this function now?
>> >
>> > There are a few opened questions:
>> >
>> > * immutable parameters of aggregate functions
>> >
>> > * effective implementation when data are in memory
>> >
>> > * effective implementation when data are out of memory
>> >
>> > * effective implementation for usage as window function - running
>> > median.
>> >
>> > Better than before, we can choose between hashing and sorting based
>> > aggregation. But tuplesort implementation is not right for using as
>> > window function. Second issue can be a not possible reusing of
>> > tuplesort for more final functions - median, percentile in one query.
>> >
>> > Ideas how to solve this task? Can we move forward in some points?
>>
>> Take a look at the standard-compliant WITHIN GROUP that is currently in
>> development for 9.4.
>>
>> http://www.postgresql.org/message-id/2b8b55b8ba82f83ef4e6070b95fb0cd0@news-out.riddles.org.uk
>>
>> --
>> Vik
>>
>
Thanks a ton!
We will definitely look at supporting at the two functions you mentioned.
Regards,
Atri
--
Regards,
Atri
l'apprenant
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