Re: [WIP PATCH] Index scan offset optimisation using visibility map - Mailing list pgsql-hackers

From Andrey Borodin
Subject Re: [WIP PATCH] Index scan offset optimisation using visibility map
Date
Msg-id 8C1D07DD-3D97-4466-B2BE-5EE6B563ECE5@yandex-team.ru
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In response to Re: [WIP PATCH] Index scan offset optimisation using visibility map  (Andrey Borodin <x4mmm@yandex-team.ru>)
Responses Re: [WIP PATCH] Index scan offset optimisation using visibility map  (Michail Nikolaev <michail.nikolaev@gmail.com>)
List pgsql-hackers
Hi, Michail!

Here are points that we need to address before advancing the patch.

> 20 февр. 2018 г., в 11:45, Andrey Borodin <x4mmm@yandex-team.ru> написал(а):
>
> Minor spots:
> There are some trailing whitespaces at line ends
>> Offset cannot be optimized because parallel execution
> I'd replace with
>> Offset cannot be optimized [in spite of | due to] parallel execution
>

> From my point of view, you should add to patch some words here
> https://www.postgresql.org/docs/current/static/indexes-index-only-scans.html

And few thoughts about plan cost estimation. Plz check create_limit_path() logic on cost estimation. I don't think you
haveenough information there to guess about possibility of IoS offset computation. 
> I do not know if it is possible to take into account this optimization in cost estimation.
> Does Limit node take cost of scanning into startup cost?

I'm marking patch as WoA, plz ping it to Need Review when done.

Thanks!

Best regards, Andrey Borodin.

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