On Mon, May 24, 2021 at 2:50 PM Michael Paquier <michael@paquier.xyz> wrote: > > On Mon, May 24, 2021 at 12:04:37PM +1000, Greg Nancarrow wrote: > > Keep cfbot happy, use the PG14 patch as latest. > > This stuff is usually very tricky.
Agreed. That's why I was looking for experts in this snapshot-handling code, to look closer at this issue, check my proposed fix, come up with a better solution etc.
>Do we have a way to reliably > reproduce the report discussed here?
Using a recipe similar to what has been described above in the thread, I reliably reproduced the bug in many Postgres versions. (v.11, v.13 etc.).
1. Make & make install
2. Make check
3. run SubTransGetTopmostTransaction-rep.sh in the Postgres source code dir.
The test fails with coredumps in around 10 minutes. With applied fix has never failed yet.
(Though transaction snapshots kitchen is indeed tricky and I am not 100% sure the fix does right thing which is safe in all circumstances)