Re: refactoring basebackup.c

On Tue, Mar 15, 2022 at 6:33 AM Jeevan Ladhe <jeevanladhe(dot)os(at)gmail(dot)com> wrote:
> I get following error at my end:
>
> $ pg_basebackup -D /tmp/zstd_bk -Ft -Xfetch --compress=server-zstd:7(at)4
> pg_basebackup: error: could not initiate base backup: ERROR: could not compress data: Unsupported parameter
> pg_basebackup: removing data directory "/tmp/zstd_bk"
>
> This is mostly because I have the zstd library version v1.4.4, which
> does not have default support for parallel workers. Maybe we should
> have a better error, something that is hinting that the parallelism is
> not supported by the particular build.

I'm not averse to trying to improve that error message, but honestly
I'd consider that to be good enough already to be acceptable. We could
think about trying to add an errhint() telling you that the problem
may be with your libzstd build.

> The regression for pg_verifybackup test 008_untar.pl also fails with a
> similar error. Here, I think we should have some logic in regression to
> skip the test if the parameter is not supported?

Or at least to have the test not fail.

> Also, just a thought, for the versions where parallelism is not
> supported, should we instead just throw a warning and fall back to
> non-parallel behavior?

I don't think so. I think it's better for the user to get an error and
then change their mind and request something we can do.

--
Robert Haas
EDB: http://www.enterprisedb.com