Message-ID: <1ab1c1cb-05c0-f524-2deb-8670b1c139ce@gmail.com>
Date: Mon, 30 Jan 2023 15:02:37 +0530
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Thunderbird/102.4.2
Subject: Re: Todo: Teach planner to evaluate multiple windows in the optimal
 order
To: John Naylor <john.naylor@enterprisedb.com>
Cc: David Rowley <dgrowleyml@gmail.com>,
 pghackers <pgsql-hackers@lists.postgresql.org>,
 Vik Fearing <vik@postgresfriends.org>
References: <83d80853-a45c-d85c-68eb-59acfe7fb5fb@gmail.com>
 <2040c902-32b1-46c8-0b26-d3f43a16b9bb@gmail.com>
 <12f6ef19-e06e-8ea9-ad98-3fd92afb7f0b@gmail.com>
 <CAApHDvp=YnmEQ8Ceu5g4wPL-b5YKmhQ7A3Lya6x=6ga=LLHMFA@mail.gmail.com>
 <8d0b24ce-f8ba-cd63-82ae-be853b4067e8@gmail.com>
 <CAApHDvpigtPVJOJ4EmWOAODtPTccz=L_gdPXDVgG2Z=iSPfNmQ@mail.gmail.com>
 <b1df021b-e6c0-f26a-1d5a-bd07f765db62@gmail.com>
 <CAApHDvqVjeHg6UgeCvFOa-uCaEFix9C_3YaT2qxsMtjN4oKbNQ@mail.gmail.com>
 <4ef7f947-526b-c4ec-f7a0-8b4586e693e4@gmail.com>
 <CAApHDvra7JeUm+wRpS+XoYXun_9b601s6ujWVG+gOd_AP5cADw@mail.gmail.com>
 <8599211e-1ea9-8827-4b9b-adeb865656bd@gmail.com>
 <CAApHDvpAO5H_L84kn9gCJ_hihOavtmDjimKYyftjWtF69BJ=8Q@mail.gmail.com>
 <a1c1f93a-16f7-4f8a-4562-4b89dd2e371c@gmail.com>
 <5314d2fc-76b6-c4ea-c083-1ef11411e5be@gmail.com>
 <CAApHDvqh+qOHk4sbvvy=Qr2NjPqAAVYf82oXY0g=Z2hRpC2Vmg@mail.gmail.com>
 <47f5b0ff-f947-f4ea-3f22-2ad0317a5214@gmail.com>
 <CAFBsxsEW-eRv5GephFO-Y=vQs_MjaEKn-1wpf2=6V7EH+SpUjg@mail.gmail.com>
Content-Language: en-US
From: Ankit Kumar Pandey <itsankitkp@gmail.com>
In-Reply-To: <CAFBsxsEW-eRv5GephFO-Y=vQs_MjaEKn-1wpf2=6V7EH+SpUjg@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit
Archived-At: <https://www.postgresql.org/message-id/1ab1c1cb-05c0-f524-2deb-8670b1c139ce%40gmail.com>
Precedence: bulk


 > On 30/01/23 11:01, John Naylor wrote:

 > Since David referred to L3 size as the starting point of a possible 
configuration parameter, that's actually cache-conscious.

Okay, makes sense. I am correcting error on my part.


 > I'm not close enough to this thread to guess at the right direction 
(although I hope related work will help), but I have a couple general 
remarks:

 > 1. In my experience, academic papers like to test sorting with 
register-sized numbers or strings. Our sorttuples are bigger, have 
complex comparators, and can fall back to fields in the full tuple.
 > 2. That paper is over 20 years old. If it demonstrated something 
genuinely useful, some of those concepts would likely be implemented in 
the real-world somewhere. Looking for evidence of that might be a good 
exercise.
 > 3. 20 year-old results may not carry over to modern hardware.
 > 4. Open source software is more widespread in the academic world now 
than 20 years ago, so papers with code (maybe even the author's github) 
are much more useful to us in my view.
 > 5. It's actually not terribly hard to make sorting faster for some 
specific cases -- the hard part is keeping other inputs of interest from 
regressing.
 > 6. The bigger the change, the bigger the risk of regressing somewhere.

Thanks John, these inputs are actually what I was looking for. I will do 
more research based on these inputs and build up my understanding.


Regards,

Ankit