Re: refactoring basebackup.c

On Mon, Jan 31, 2022 at 6:11 AM Jeevan Ladhe
<jeevan(dot)ladhe(at)enterprisedb(dot)com> wrote:
> I had an offline discussion with Dipesh, and he will be working on the
> lz4 client side decompression part.

OK. I guess we should also be thinking about client-side LZ4
compression. It's probably best to focus on that before worrying about
ZSTD, even though ZSTD would be really cool to have.

>> - In the new test case you set decompress_flags but according to the
>> documentation I have here, -m is for multiple files (and so should not
>> be needed here) and -d is for decompression (which is what we want
>> here). So I'm confused why this is like this.
>
> As explained earlier in the tap test the 'lz4 -d base.tar.lz4' command was
> throwing the decompression to stdout. Now, I have removed the '-m',
> added '-d' for decompression, and also added the target file explicitly in
> the command.

I don't see the behavior you describe here. For me:

[rhaas ~]$ lz4 q.lz4
Decoding file q
q.lz4 : decoded 3785 bytes
[rhaas ~]$ rm q
[rhaas ~]$ lz4 -m q.lz4
[rhaas ~]$ ls q
q
[rhaas ~]$ rm q
[rhaas ~]$ lz4 -d q.lz4
Decoding file q
q.lz4 : decoded 3785 bytes
[rhaas ~]$ rm q
[rhaas ~]$ lz4 -d -m q.lz4
[rhaas ~]$ ls q
q

In other words, on my system, the file gets decompressed with or
without -d, and with or without -m. The only difference I see is that
using -m makes it happen silently, without printing anything on the
terminal. Anyway, I wasn't saying that using -m was necessarily wrong,
just that I didn't understand why you had it like that. Now that I'm
more informed, I recommend that we use -d -m, the former to be
explicit about wanting to decompress and the latter because it either
makes it less noisy (on my system) or makes it work at all (on yours).
It's surprising that the command behavior would be different like that
on different systems, but it is what it is. I think any set of flags
we put here is better than adding more logical in perl, as it keeps
things simpler.

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