Horton

Re: Bug in nbtree optimization to skip > operator comparisons (or < comparisons in backwards scans)

Peter Geoghegan <pg@bowt.ie>

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From: Peter Geoghegan <pg@bowt.ie>
To: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Cc: Alexander Korotkov <aekorotkov@gmail.com>, Heikki Linnakangas <hlinnaka@iki.fi>, Matthias van de Meent <boekewurm+postgres@gmail.com>
Date: 2023-12-06T01:45:41Z
Lists: pgsql-hackers

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On Tue, Dec 5, 2023 at 4:41 PM Peter Geoghegan <pg@bowt.ie> wrote:
> "In general, when inequality keys are present, the initial-positioning
> code only promises to position before the first possible match, not
> exactly at the first match, for a forward scan; or after the last
> match for a backward scan."
>
> My test case mostly just demonstrates how to reproduce the scenario
> described by this sentence.

I just realized that my test case wasn't quite minimized correctly. It
depended on a custom function that was no longer created.

Attached is a revised version that uses btint84cmp instead.

-- 
Peter Geoghegan

Commits

  1. Fix an oversight in refactoring in 06b10f80ba4.

  2. Make RangeTblEntry dump order consistent

  3. Improvements and fixes for e0b1ee17dc

  4. Remove BTScanOpaqueData.firstPage

  5. Optimize nbtree backward scan boundary cases.

  6. Skip checking of scan keys required for directional scan in B-tree