Re: Add LZ4 compression in pg_dump

------- Original Message -------
On Friday, January 27th, 2023 at 6:23 PM, Justin Pryzby <pryzby(at)telsasoft(dot)com> wrote:

>
>
> On Thu, Jan 26, 2023 at 12:22:45PM -0600, Justin Pryzby wrote:
>
> > That commit also added this to pg-dump.c:
> >
> > + case PG_COMPRESSION_ZSTD:
> > + pg_fatal("compression with %s is not yet supported", "ZSTD");
> > + break;
> > + case PG_COMPRESSION_LZ4:
> > + pg_fatal("compression with %s is not yet supported", "LZ4");
> > + break;
> >
> > In 002, that could be simplified by re-using the supports_compression()
> > function. (And maybe the same in WriteDataToArchive()?)
>
>
> The first patch aims to minimize references to ".gz" and "GZIP" and
> ZLIB. pg_backup_directory.c comments still refers to ".gz". I think
> the patch should ideally change to refer to "the compressed file
> extension" (similar to compress_io.c), avoiding the need to update it
> later.
>
> I think the file extension stuff could be generalized, so it doesn't
> need to be updated in multiple places (pg_backup_directory.c and
> compress_io.c). Maybe it's useful to add a function to return the
> extension of a given compression method. It could go in compression.c,
> and be useful in basebackup.
>
> For the 2nd patch:
>
> I might be in the minority, but I still think some references to "gzip"
> should say "zlib":
>
> +} GzipCompressorState;
> +
> +/* Private routines that support gzip compressed data I/O */
> +static void
> +DeflateCompressorGzip(ArchiveHandle *AH, CompressorState *cs, bool flush)
>
> In my mind, three things here are misleading, because it doesn't use
> gzip headers:
>
> | GzipCompressorState, DeflateCompressorGzip, "gzip compressed".
>
> This comment is about exactly that:
>
> * underlying stream. The second API is a wrapper around fopen/gzopen and
> * friends, providing an interface similar to those, but abstracts away
> * the possible compression. Both APIs use libz for the compression, but
> * the second API uses gzip headers, so the resulting files can be easily
> * manipulated with the gzip utility.
>
> AIUI, Michael says that it's fine that the user-facing command-line
> options use "-Z gzip" (even though the "custom" format doesn't use gzip
> headers). I'm okay with that, as long as that's discussed/understood.
>

Thank you for the input Justin. I am currently waiting for input from a
third person to get some conclusion. I thought that it should be stated
before my inactiveness is considered as indifference, which is not.

Cheers,
//Georgios

> --
> Justin