Re: wrong fds used for refilenodes after pg_upgrade relfilenode changes Reply-To:

On Wed, Feb 09, 2022 at 02:00:04PM -0800, Andres Freund wrote:
> On linux we can do so by a) checking if readlink(/proc/self/fd/$fd) points to
> a filename ending in " (deleted)", b) doing fstat(fd) and checking if st_nlink
> == 0.

You could also stat() the file in proc/self/fd/N and compare st_ino.  It
"looks" like a symlink (in which case that wouldn't work) but it's actually a
Very Special File.  You can even recover deleted, still-opened files that way..

PS. I didn't know pg_upgrade knew about Reply-To ;)