Re: Regression failures after changing PostgreSQL blocksize

Hi,

Thank you all for providing invaluable information. Based on the answers,
it's clear that regression failures with custom block sizes are expected
and not necessarily indicative of functional bugs.
However, it creates doubts, so, can we add alternative test output files
for the changes caused by different block sizes? E.g: the attached poc
patch. Whether such an approach would be acceptable?

Which other compile time options are expected to cause test failures?

Regards,

Yasir Hussain Shah
Data Bene

On Thu, Feb 12, 2026 at 7:49 AM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> Zhang Mingli <zmlpostgres(at)gmail(dot)com> writes:
> >> On Thu, Feb 12, 2026 at 7:19 AM Yasir <yasir(dot)hussain(dot)shah(at)gmail(dot)com>
> wrote:
> >>> This produced so many regression failures. I'm wondering, are such
> failures typical/expected when altering the default block size?
>
> > Our experience shows that when changing the block size, most of the
> regression test differences are expected — they often reflect output
> variations (like buffer counts, cost estimates, or physical storage
> details) rather than functional bugs.
> > That said, it really needs to be examined case by case.
>
> Indeed. There is relevant documentation here:
>
> https://www.postgresql.org/docs/current/regress-evaluation.html
>
> (Some of that looks a bit out of date, ie differences we don't really
> expect to happen anymore. But plan changes and row-ordering changes
> are definitely expected if you change any parameter that affects
> planner cost estimates.)
>
> regards, tom lane
>