Re: Yet another fast GiST build

From: Heikki Linnakangas <hlinnaka(at)iki(dot)fi>
To: Andrey Borodin <x4mmm(at)yandex-team(dot)ru>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Justin Pryzby <pryzby(at)telsasoft(dot)com>, Darafei Komяpa Praliaskouski <me(at)komzpa(dot)net>, Pavel Borisov <pashkin(dot)elfe(at)gmail(dot)com>, Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, Michael Paquier <michael(at)paquier(dot)xyz>, Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Yet another fast GiST build
Date: 2020-10-07 12:38:20
Message-ID: 6dda35ae-6760-2349-6589-c6bc87d23d1c@iki.fi
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On 07/10/2020 15:27, Andrey Borodin wrote:
> Here's draft patch with implementation of sortsupport for ints and floats.

> +static int
> +gbt_int4_cmp(Datum a, Datum b, SortSupport ssup)
> +{
> + int32KEY *ia = (int32KEY *) DatumGetPointer(a);
> + int32KEY *ib = (int32KEY *) DatumGetPointer(b);
> +
> + if (ia->lower == ib->lower)
> + {
> + if (ia->upper == ib->upper)
> + return 0;
> +
> + return (ia->upper > ib->upper) ? 1 : -1;
> + }
> +
> + return (ia->lower > ib->lower) ? 1 : -1;
> +}

We're only dealing with leaf items during index build, so the 'upper'
and 'lower' should always be equal here, right? Maybe add a comment and
an assertion on that.

(It's pretty sad that the on-disk representation is identical for leaf
and internal items, because that wastes a lot of disk space, but that's
way out of scope for this patch.)

- Heikki

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