Re: Simplifications for error messages related to compression

On Tue, Dec 20, 2022 at 08:29:32PM -0600, Justin Pryzby wrote:
> - pg_fatal("not built with zlib support");
> + pg_fatal("this build does not support compression with %s", "gzip");
>
> I tried to say in the other thread that gzip != zlib.
>
> This message may be better for translation, but (for WriteDataToArchive
> et al) the message is now less accurate, and I suspect will cause some
> confusion.

Compression specifications use this term, so, like bbstreamer_gzip.c,
that does not sound like a big difference to me as everything depends
on HAVE_LIBZ, still we use gzip for all the user-facing terms.

> 5e73a6048 introduced a similar user-facing issue: pg_dump -Fc -Z gzip
> does not output a gzip.

We've never mentioned any compression method in the past docs, just
that things can be compressed.

> $ ./tmp_install/usr/local/pgsql/bin/pg_dump -h /tmp -Fc -Z gzip regression |xxd |head
> 00000000: 5047 444d 5001 0e00 0408 0101 0100 0000 PGDMP...........
>
> I'm okay with it if you think this is no problem - maybe it's enough to
> document that the output is zlib and not gzip.

Perhaps.

> Otherwise, one idea was to reject "gzip" with -Fc. It could accept
> integers only.

I am not sure what we would gain by doing that, except complications
with the code surrounding the handling of compression specifications,
which is a backward-compatible thing as it can handle integer-only
inputs.

> BTW I think it's helpful to include the existing participants when
> forking a thread.

Err, okay.. Sorry about that.
--
Michael