Horton

Re: Incorrect result of bitmap heap scan.

Peter Geoghegan <pg@bowt.ie>

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From: Peter Geoghegan <pg@bowt.ie>
To: Andres Freund <andres@anarazel.de>
Cc: Matthias van de Meent <boekewurm+postgres@gmail.com>, Andrew Dunstan <andrew@dunslane.net>, Melanie Plageman <melanieplageman@gmail.com>, Thomas Munro <thomas.munro@gmail.com>, Konstantin Knizhnik <knizhnik@garret.ru>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>, Alexander Kuzmenkov <akuzmenkov@timescale.com>, Tom Lane <tgl@sss.pgh.pa.us>, Heikki Linnakangas <hlinnaka@iki.fi>
Date: 2024-12-03T01:22:34Z
Lists: pgsql-hackers 
On Mon, Dec 2, 2024 at 3:56 PM Peter Geoghegan <pg@bowt.ie> wrote:
> I took what you wrote, and repurposed it to prove my old theory about
> GiST index-only scans being broken due to the lack of an appropriate
> interlock against concurrent TID recycling. See the attached patch.

I've moved discussion of this GiST bug over to the old 2021 thread
where I first raised concerns about the issue:

https://postgr.es/m/CAH2-Wz=jjiNL9FCh8C1L-GUH15f4WFTWub2x+_NucngcDDcHKw@mail.gmail.com

The GiST bug is actually causally unrelated to the bitmap index scan
bug under discussion, despite the high-level similarity. Seems best to
keep discussion of GiST on its own thread, for that reason.

-- 
Peter Geoghegan

Commits

  1. Add test for HeapBitmapScan's broken skip_fetch optimization

  2. Remove HeapBitmapScan's skip_fetch optimization

  3. Allow bitmap scans to operate as index-only scans when possible.