Re: [PATCH] distinct aggregates within a window function WIP

From: Eugen Konkov <kes-kes(at)yandex(dot)ru>
To: Andreas Karlsson <andreas(at)proxel(dot)se>, PostgreSQL-development <pgsql-hackers(at)postgreSQL(dot)org>
Subject: Re: [PATCH] distinct aggregates within a window function WIP
Date: 2020-04-22 07:05:19
Message-ID: 186624638.20200422100519@yandex.ru
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Hello Andreas,

Tuesday, April 21, 2020, 6:17:00 PM, you wrote:

> On 4/21/20 5:06 PM, Eugen Konkov wrote:
>> Hi. I read the thread.
>>
>> Probably this fiddle will be helpful for testing:
>>
>> https://dbfiddle.uk/?rdbms=postgres_12&fiddle=abe845142a5099d921d3729043fb8491
>>
>> I recently encountered a problem:
>> Why Window-specific functions do not allow DISTINCT to be used within the function argument list?
>>
>> sum( DISTINCT order_cost ) OVER ( PARTITION BY invoice_id ORDER BY invoice_id, group_id RANGE unbound preceeding and unbound following )
>>
>> behavior is quite deterministic:
>>
>> ORDER BY will create peers in partition
>> DISTINCT will get only one peer
>>
>> I resolve my problem via two subqueries, but it seems this logic may
>> be applied to window functions (did not check this for other functions thought)

> Sorry, I do not follow. What problem did you encounter?

Lack of DISTINCT for window function SUM

--
Best regards,
Eugen Konkov

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