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 ;)
