Thanks for the patch, Dipesh.
I had a look at the patch and also tried to take the backup. I have
following suggestions and observations:
I get following error at my end:
$ pg_basebackup -D /tmp/zstd_bk -Ft -Xfetch --compress=server-zstd:7@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.
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?
+ if (ZSTD_isError(ret))
+ elog(ERROR,
+ "could not compress data: %s",
+ ZSTD_getErrorName(ret));
I think all of this can go on one line, but anyhow we have to improve
the error message here.
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?
Regards,
Jeevan Ladhe
On Mon, 14 Mar 2022 at 21:41, Dipesh Pandit <dipesh.pan...@gmail.com> wrote:
> Hi,
>
> I tried to implement support for parallel ZSTD compression. The
> library provides an option (ZSTD_c_nbWorkers) to specify the
> number of compression workers. The number of parallel
> workers can be set as part of compression parameter and if this
> option is specified then the library performs parallel compression
> based on the specified number of workers.
>
> User can specify the number of parallel worker as part of
> --compress option by appending an integer value after at sign (@).
> (-Z, --compress=[{client|server}-]{gzip|lz4|zstd}[:LEVEL][@WORKERS])
>
> Please find the attached patch v1 with the above changes.
>
> Note: ZSTD library version 1.5.x supports parallel compression
> by default and if the library version is lower than 1.5.x then
> parallel compression is enabled only the source is compiled with build
> macro ZSTD_MULTITHREAD. If the linked library version doesn't
> support parallel compression then setting the value of parameter
> ZSTD_c_nbWorkers to a value other than 0 will be no-op and
> returns an error.
>
> Thanks,
> Dipesh
>
