Horton

Re: Yet another fast GiST build

Kyotaro Horiguchi <horikyota.ntt@gmail.com>

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From: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
To: x4mmm@yandex-team.ru
Cc: hlinnaka@iki.fi, me@komzpa.net, pashkin.elfe@gmail.com, thomas.munro@gmail.com, michael@paquier.xyz, a.korotkov@postgrespro.ru, pgsql-hackers@postgresql.org
Date: 2020-09-16T09:09:03Z
Lists: pgsql-hackers 
At Wed, 16 Sep 2020 12:27:09 +0500, "Andrey M. Borodin" <x4mmm@yandex-team.ru> wrote in 
> I was thinking that machine epsilon is near 1e-300, but I was
> wrong. It's actually near 1e-15.

FWIW, the mantissa of double is effectively 52+1 bits, about 15.9
digits. so 1+(1e-16) is basically indistincitve from
1+(2e-16). Actually two double precisions 1+2e-16 and 1+3e-16 are
indistinctive from each other.

> Actually, I just want to understand what changes between v18 and v19 changed on-page order of items. I look into patch diff and cannot figure it out. There are only logging changes. How this affects scan?

FWIW, I saw the same symptom by my another patch after adding a value
to POINT_TBL. (But I didn't pursue the cause further..)

regards.

-- 
Kyotaro Horiguchi
NTT Open Source Software Center

Commits

  1. Add sortsupport for gist_btree opclasses, for faster index builds.

  2. pageinspect: Fix relcache leak in gist_page_items().

  3. Fix test failure with wal_level=minimal.

  4. Enhance nbtree index tuple deletion.

  5. Fix portability issues in the new gist pageinspect test.

  6. Add functions to 'pageinspect' to inspect GiST indexes.

  7. Fix missing validation for the new GiST sortsupport functions.

  8. Fix compilation warning in xlog.c

  9. Set right-links during sorted GiST index build.

  10. Fix checksum calculation in the new sorting GiST build.

  11. Add support for building GiST index by sorting.