Re: [PATCH] Incremental sort (was: PoC: Partial sort)

From: James Coleman <jtc331(at)gmail(dot)com>
To: Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>
Cc: Justin Pryzby <pryzby(at)telsasoft(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Michael Paquier <michael(at)paquier(dot)xyz>, Rafia Sabih <rafia(dot)pghackers(at)gmail(dot)com>, Peter Geoghegan <pg(at)bowt(dot)ie>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Shaun Thomas <shaun(dot)thomas(at)2ndquadrant(dot)com>, Dmitry Dolgov <9erthalion6(at)gmail(dot)com>, Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru>, PostgreSQL Developers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>, Andreas Karlsson <andreas(at)proxel(dot)se>
Subject: Re: [PATCH] Incremental sort (was: PoC: Partial sort)
Date: 2020-04-07 23:50:26
Message-ID: CAAaqYe9+krh8swV2tvZA2N0QgbjRSsaYw5JgmfM9pjgnTVRyMw@mail.gmail.com
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On Tue, Apr 7, 2020 at 7:02 PM Tomas Vondra
<tomas(dot)vondra(at)2ndquadrant(dot)com> wrote:
>
> On Mon, Apr 06, 2020 at 11:25:21PM -0500, Justin Pryzby wrote:
> >On Mon, Apr 06, 2020 at 09:57:22PM +0200, Tomas Vondra wrote:
> >> I've pushed the fist part of this patch series - I've reorganized it a
> >
> >I scanned through this again post-commit. Find attached some suggestions.
> >
>
> Thanks. The typo fixes seem clear, except for this bit:
>
> * If we've set up either of the sort states yet, we need to reset them.
> * We could end them and null out the pointers, but there's no reason to
> * repay the setup cost, and because ???? guard setting up pivot comparator
> * state similarly, doing so might actually cause a leak.
>
> I can't figure out what ???? should be. James, do you recall what this
> should be?

Yep, it's ExecIncrementalSort. If you look for the block guarded by
`if (fullsort_state == NULL)` you'll see the call to
preparePresortedCols(), which sets up the pivot comparator state
referenced by this comment.

James

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