On Mon, May 8, 2023 at 4:10 AM Evgeny Morozov
<postgresql3@realityexists.net> wrote:
> On 6/05/2023 11:13 pm, Thomas Munro wrote:
> > Would you like to try requesting FILE_COPY for a while and see if it eventually happens like that too?
> Sure, we can try that.
Maybe you could do some one way and some the other, so that we try to
learn more?
> Ubuntu 18.04.6
> Kernel 4.15.0-206-generic #217-Ubuntu SMP Fri Feb 3 19:10:13 UTC 2023
> x86_64 x86_64 x86_64 GNU/Linux
> zfsutils-linux package version 0.7.5-1ubuntu16.12 amd64
I tried for a few hours to reproduce this by trying to make as many
things as similar to yours as I could based on info in this thread
(Linux: up-to-date Ubuntu 18.04 in vagrant which has nearly the same
kernel 4.15.0-208-generic and a close but slightly different version
of ancient ZFS 0.7.5-1ubuntu15, not sure why, ZFS: mirror (I used a
pair of loopback files), recordsize=16kB, compression=lz4, PG:
compiled from tag REL_15_2, data_checksums=on, full_page_writes=off,
wal_recycle=off, wal_init_zero=off), with what I thought might be
roughly what you're doing (creating three DBs, two clones of the
first, with various modification at various points, with various
overlapping activities, and then checking for catalog corruption). No
cigar. Hrmph.
My first thought on this was along the lines of previous comments.
We are writing the initial pieces of the files for a new DATABASE.
Some flag is set, and then context is lost, and it ends up that a SAVE happens
to an existing DATABASE.
So, my thought was a parallel set of UPDATE "type" commands that would
cause those types of pages for a stable/existing DB to be updated/written.
It could be as simple as creating temp tables in the other database (since I believe pg_class was hit).
From a "rare" standpoint. That "feels" about right to me. It would pass serial tests (like you are running).
Just a thought. Maybe a simple background script creating temp tables in another DB.
Also, not sure if the OP has a set of things done after he creates the DB that may help?
Kirk