Re: Add LZ4 compression in pg_dump

On Sun, Mar 27, 2022 at 12:06 PM Justin Pryzby <pryzby(at)telsasoft(dot)com> wrote:
> Maybe it should take an argument which specifies the default algorithm to use
> for input of a numeric "level". And reject such input if not specified, since
> wal_compression has never taken a "level", so it's not useful or desirable to
> have that default to some new algorithm.

That sounds odd to me. Wouldn't it be rather confusing if a bare
integer meant gzip for one case and lz4 for another?

> I could write this down if you want, although I'm not sure how/if you intend
> other people to use bc_algorithm and bc_algorithm. I don't think it's
> important to do for v15, but it seems like it could be done after featue
> freeze. pg_dump+lz4 is targetting v16, although there's a cleanup patch that
> could also go in before branching.

Well, I think the first thing we should do is get rid of enum
WalCompressionMethod and use enum WalCompression instead. They've got
the same elements and very similar names, but the WalCompressionMethod
ones just have names like COMPRESSION_NONE, which is too generic,
whereas WalCompressionMethod uses WAL_COMPRESSION_NONE, which is
better. Then I think we should also rename the COMPR_ALG_* constants
in pg_dump.h to names like DUMP_COMPRESSION_*. Once we do that we've
got rid of all the unprefixed things that purport to be a list of
compression algorithms.

Then, if people are willing to adopt the syntax that the
backup_compression.c/h stuff supports as a project standard (+1 from
me) we can go the other way and rename that stuff to be more generic,
taking backup out of the name.

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