From: Tom Lane <tgl@sss.pgh.pa.us>
To: Gavin Flower <GavinFlower@archidevsys.co.nz>
cc: pgsql-hackers@lists.postgresql.org
Subject: Re: Add proper planner support for ORDER BY / DISTINCT aggregates
In-reply-to: <17027322-8a85-5803-c86a-4025f6155980@archidevsys.co.nz>
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Comments: In-reply-to Gavin Flower <GavinFlower@archidevsys.co.nz>
	message dated "Sat, 03 Jul 2021 08:37:40 +1200"
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Date: Fri, 02 Jul 2021 16:51:51 -0400
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Gavin Flower <GavinFlower@archidevsys.co.nz> writes:
> On 2/07/21 8:39 pm, David Rowley wrote:
>> That's a good question. There was an argument in [1] that mentions
>> that there might be a group of people who rely on aggregation being
>> done in a certain order where they're not specifying an ORDER BY
>> clause in the aggregate.  If that group of people exists, then it's
>> possible they might be upset in the scenario that you describe.

> So I think that pg has no obligation to protect the sensibilities of 
> naive users in this case, especially at the expense of users that want 
> queries to complete as quickly as possible.  IMHO

I agree.  We've broken such expectations in the past and I don't
have much hesitation about breaking them again.

			regards, tom lane