Re: Add LZ4 compression in pg_dump

From: Michael Paquier <michael(at)paquier(dot)xyz>
To: Justin Pryzby <pryzby(at)telsasoft(dot)com>
Cc: gkokolatos(at)pm(dot)me, Rachel Heaton <rachelmheaton(at)gmail(dot)com>, Greg Stark <stark(at)mit(dot)edu>, pgsql-hackers(at)lists(dot)postgresql(dot)org
Subject: Re: Add LZ4 compression in pg_dump
Date: 2022-03-29 07:27:32
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On Sat, Mar 26, 2022 at 01:14:41AM -0500, Justin Pryzby wrote:
> See 0001 and the manpage.
> + 'pg_dump: compression is not supported by tar archive format');
> When I submitted a patch to support zstd, I spent awhile trying to make
> compression work with tar, but it's a significant effort and better done
> separately.

Wow. This stuff is old enough to vote (c3e18804), dead since its
introduction. There is indeed an argument for removing that, it is
not good to keep around that that has never been stressed and/or
used. Upon review, the cleanup done looks correct, as we have never
been able to generate .dat.gz files in for a dump in the tar format.

+ command_fails_like(
+ [ 'pg_dump', '--compress', '1', '--format', 'tar' ],
This addition depending on HAVE_LIBZ is a good thing as a reminder of
any work that could be done in 0002. Now that's waiting for 20 years
so I would not hold my breath on this support. I think that this
could be just applied first, with 0002 on top of it, as a first

+ compress_cmd => [
Patch 0001 is missing and update of pg_dump's Makefile to pass down
this environment variable to the test scripts, no?

+ compress_cmd => [
+ '-f',
+ '-k', '-d',
-f and -d are available everywhere I looked at, but is -k/--keep a
portable choice with a gzip command? I don't see this option in
OpenBSD, for one. So this test is going to cause problems on those
buildfarm machines, at least. Couldn't this part be replaced by a
simple --test to check that what has been compressed is in correct
shape? We know that this works, based on our recent experiences with
the other tests.

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