Re: Teach pg_receivewal to use lz4 compression

On Tue, Jun 29, 2021 at 8:15 PM <gkokolatos(at)pm(dot)me> wrote:
>
> Hi,
>
> The program pg_receivewal can use gzip compression to store the received WAL.
> This patch teaches it to be able to use lz4 compression if the binary is build
> using the -llz4 flag.

+1 for the idea

Some comments/suggestions on the patch

1.
@@ -90,7 +91,8 @@ usage(void)
printf(_(" --synchronous flush write-ahead log immediately
after writing\n"));
printf(_(" -v, --verbose output verbose messages\n"));
printf(_(" -V, --version output version information, then exit\n"));
- printf(_(" -Z, --compress=0-9 compress logs with given
compression level\n"));
+ printf(_(" -I, --compress-program use this program for compression\n"));

Wouldn't it be better to call it compression method instead of
compression program?

2.
+ printf(_(" -Z, --compress=0-9 compress logs with given
compression level (available only with compress-program=zlib)\n"));

I think we can somehow use "acceleration" parameter of lz4 compression
to map on compression level, It is not direct mapping but
can't we create some internal mapping instead of completely ignoring
this option for lz4, or we can provide another option for lz4?

3. Should we also support LZ4 compression using dictionary?

--
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com