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Date: Tue, 24 Sep 2019 09:06:27 -0300
From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Cc: 9erthalion6@gmail.com, florisvannee@optiver.com,
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Subject: Re: Index Skip Scan
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Precedence: bulk

On 2019-Sep-24, Kyotaro Horiguchi wrote:

> Sorry, it's not a boolean. A tristate value. From the definition
> (Back, NoMove, Forward) = (-1, 0, 1), (dir1 == -dir2) if
> NoMovement did not exist. If it is not guranteed,
> 
> (dir1 != 0 && dir1 == -dir2) ?

Maybe just add ScanDirectionIsOpposite(dir1, dir2) with that
definition? :-)

-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services