Re: Incorrect result of bitmap heap scan.

Matthias van de Meent <boekewurm+postgres@gmail.com>

From: Matthias van de Meent <boekewurm+postgres@gmail.com>

To: Peter Geoghegan <pg@bowt.ie>, Tom Lane <tgl@sss.pgh.pa.us>

Cc: Andres Freund <andres@anarazel.de>, 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>

Date: 2025-03-05T11:12:57Z

Lists: pgsql-hackers

Attachments

v5-0002-isolationtester-showing-broken-index-only-bitmap-.patch (application/octet-stream) patch v5-0002
v5-0001-Remove-HeapBitmapScan-s-skip_fetch-optimization.patch (application/octet-stream) patch v5-0001

On Sun, 2 Mar 2025 at 01:35, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>
> Peter Geoghegan <pg@bowt.ie> writes:
> > Is everybody in agreement about committing and back patching this fix,
> > which simply disables the optimization altogether?
> > I myself don't see a better way, but thought I'd ask before proceeding
> > with review and commit.
>
> If you don't see a clear path forward, then "disable" is the only
> reasonable choice for the back branches.  Maybe we'll find a fix
> in future, but it seems unlikely that it'd be back-patchable.

Agreed.

Here's patch v5 for the master branch (now up to f4694e0f), with no
interesting changes other than fixing apply conflicts caused by
bfe56cdf.

Kind regards,

Matthias van de Meent
Neon (https://neon.tech)

Commits

Add test for HeapBitmapScan's broken skip_fetch optimization
- 24da5b239a4b 18.0 landed
Remove HeapBitmapScan's skip_fetch optimization
- 459e7bf8e2f8 18.0 landed
- b9ec8125d167 13.21 landed
- 4934d38759cd 14.18 landed
- 77d90d6d6334 15.13 landed
- 980727b84107 16.9 landed
- 78cb2466f752 17.5 landed
Allow bitmap scans to operate as index-only scans when possible.
- 7c70996ebf09 11.0 cited