Re: Add LZ4 compression in pg_dump

On 2/25/23 15:05, Justin Pryzby wrote:
> On Fri, Feb 24, 2023 at 11:02:14PM -0600, Justin Pryzby wrote:
>> I have some fixes (attached) and questions while polishing the patch for
>> zstd compression. The fixes are small and could be integrated with the
>> patch for zstd, but could be applied independently.
>
> One more - WriteDataToArchiveGzip() says:
>
> + if (cs->compression_spec.level == 0)
> + pg_fatal("requested to compress the archive yet no level was specified");
>
> That was added at e9960732a.
>
> But if you specify gzip:0, the compression level is already enforced by
> validate_compress_specification(), before hitting gzip.c:
>
> | pg_dump: error: invalid compression specification: compression algorithm "gzip" expects a compression level between 1 and 9 (default at -1)
>
> 5e73a6048 intended that to work as before, and you *can* specify -Z0:
>
> The change is backward-compatible, hence specifying only an integer
> leads to no compression for a level of 0 and gzip compression when the
> level is greater than 0.
>
> $ time ./src/bin/pg_dump/pg_dump -h /tmp regression -t int8_tbl -Fp --compress 0 |file -
> /dev/stdin: ASCII text
>

FWIW I agree we should make this backwards-compatible - accept "0" and
treat it as no compression.

Georgios, can you prepare a patch doing that?

regards
--
Tomas Vondra
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