Re: logical decoding/replication: new functions pg_ls_logicaldir and pg_ls_replslotdir

On Fri, Oct 22, 2021 at 9:26 PM Justin Pryzby <pryzby(at)telsasoft(dot)com> wrote:
> I concluded that it's better to add a function to list metadata of an arbitrary
> dir, rather than adding more functions to handle specific, hardcoded dirs:
> https://www.postgresql.org/message-id/flat/20191227170220(dot)GE12890(at)telsasoft(dot)com

I just had a quick look at the pg_ls_dir_metadata() patch(I didn't
look at the other patches). While it's a good idea to have a single
function for all the PGDATA directories, I'm not sure if one would
ever need the info like type, change, creation path etc. If we do
this, the function will become the linux equivalent command. I don't
see the difference between modification and change time stamps. For
debugging or analytical purposes in production environments, one would
majorly look at the file name, it's size on the disk, modification
time (to decide whether the file is stale or not, creation time (to
decide how old is the file), file/directory(maybe?). I'm not sure if
your patch has a recursive option for pg_ls_dir_metadata(), if it has,
I think it's more complex from a usability perspective.

And the functions like pg_ls_tmpdir, pg_ls_tmpdir, pg_ls_waldir etc.
(existing) and pg_ls_logicaldir, pg_ls_replslotdir (yet to have) will
provide the better usability compared to a generic function. Having
said this, I don't oppose having a generic function returning the file
name, file size, modification time, creation time, but not other info,
please. If one is interested in knowing the other information file
type, path etc. they can go run linux/windows/OS commands.

In summary what I think at this point is:
1) pg_ls_logicaldir, pg_ls_replslotdir - better for usability and
serving special purpose like their peers
2) modify pg_ls_dir such that it returns the file name, file size,
modification time, creation time, for directories, to be simple, it
shouldn't go recursively over all the directories, it should just
return the directory name, size, modification time, creation time.

If okay, I'm ready to spend time implementing them.

Thoughts?

Regards,
Bharath Rupireddy.