Re: Confusing error message with too-large file in pg_basebackup

On Fri, Nov 20, 2015 at 9:37 AM, Josh Berkus <josh(at)agliodbs(dot)com> wrote:
> pg_basebackup: could not get transaction log end position from server:
> ERROR: archive member "core" too large for tar format

That's a backend-side error.

> This was very confusing to the user, because they weren't requesting tar
> format, and even setting -Fp got the same error message. I can only
> hypothesize that tar is used somewhere under the hood.

Exactly, when a base backup is taken through the replication protocol,
backend always sends it in tar format for performance reasons. It is
then up to pg_basebackup to decide if the output should be untared or
not.

> pg_basebackup doesn't need to work under these circumstances, but maybe
> we could give a less baffling error message?

We would need to let the backend know about the output format expected
by the caller of BASE_BACKUP by extending the command in the
replication protocol. It does not sound like a good idea to me just to
make some potential error messages more verbose.
--
Michael