Re: Aborted pg_dump run empties existing archive file

On Thu, May 26, 2016 at 2:48 PM, Ken Winter <ken(at)sunward(dot)org> wrote:

> I just discovered that a run of pg_dump that gets aborted empties any
> pre-existing backup file of the same name. It happens whether the run was
> deliberately canceled by the user or just failed because of a bad password
> (as in the example below).
>
> ~/dba$ pg_dump --host=localhost -U ken --format=c
> --file=mess_development.bak --no-owner --no-privileges mess_development
> Password: <CORRECT PASSWORD ENTERED>
>
> ~/dba$ ls -l mess_development.bak
> -rw-rw-r-- 1 ken ken *87070* May 26 14:20 mess_development.bak
>
> ~/dba$ pg_dump --host=localhost -U ken --format=c
> --file=mess_development.bak --no-owner --no-privileges mess_development
> Password: <BAD PASSWORD ENTERED>
> pg_dump: [archiver (db)] connection to database "mess_development" failed:
> FATAL: password authentication failed for user "ken"
> FATAL: password authentication failed for user "ken"
>
> ~/dba$ ls -l mess_development.bak
> -rw-rw-r-- 1 ken ken *0* May 26 14:21 mess_development.bak
>
> ~/dba$
>
> This is troubling because I can imagine a disaster scenario where one
> loses one's previous backup and, perhaps because of a forgotten password,
> can't generate a new one. (This scenario hasn't happened to *me* yet,
> but seems like it could.) In general, a failed run of a piece of software
> should leave everything unchanged. So maybe this is a bug that needs to be
> fixed?
>
> ~ Ken
>
>
>
>
>
>...a run of pg_dump that gets aborted empties any pre-existing backup file
of the same name

This is standard behavior. By using the same output file name, you are
telling the O/S to overwrite/delete that file and replace with new
information.
Most DBA's usually specify a date(and/or time) as a suffix to prevent that
probleb and keep several versions of backup.

Not that it in this case, but it is considered good procedure to report the
PostgreSQL version and O/S when contacting this list for support.
Please consider that for future correspondence.

--
*Melvin Davidson*
I reserve the right to fantasize. Whether or not you
wish to share my fantasy is entirely up to you.