Re: [WIP PATCH] Index scan offset optimisation using visibility map

From: Andrey Borodin <x4mmm(at)yandex-team(dot)ru>
To: Michail Nikolaev <michail(dot)nikolaev(at)gmail(dot)com>
Cc: "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: [WIP PATCH] Index scan offset optimisation using visibility map
Date: 2018-03-02 05:58:43
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Hi, Michail!

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

> 20 февр. 2018 г., в 11:45, Andrey Borodin <x4mmm(at)yandex-team(dot)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

And few thoughts about plan cost estimation. Plz check create_limit_path() logic on cost estimation. I don't think you have enough 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.


Best regards, Andrey Borodin.

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