Horton

Re: Add LZ4 compression in pg_dump

Justin Pryzby <pryzby@telsasoft.com>

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From: Justin Pryzby <pryzby@telsasoft.com>
To: gkokolatos@pm.me
Cc: Michael Paquier <michael@paquier.xyz>, Tomas Vondra <tomas.vondra@enterprisedb.com>, pgsql-hackers@lists.postgresql.org, Rachel Heaton <rachelmheaton@gmail.com>
Date: 2023-02-08T02:37:18Z
Lists: pgsql-hackers 
On Tue, Jan 31, 2023 at 09:00:56AM +0000, gkokolatos@pm.me wrote:
> > 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.

I'm not sure what there is to lose by making the names more accurate -
especially since they're private/internal-only.

Tomas marked himself as a committer, so maybe could comment.

It'd be nice to also come to some conclusion about whether -Fc -Z gzip
is confusing (due to not actually using gzip).

BTW, do you intend to merge this for v16 ?  I verified in earlier patch
versions that tests all pass with lz4 as the default compression method.
And checked that gzip output is compatible with before, and that old
dumps restore correctly, and there's no memory leaks or other errors.

-- 
Justin

Commits

  1. Advance input pointer when LZ4 compressing data

  2. Null-terminate the output buffer of LZ4Stream_gets

  3. Rework code defining default compression for dir/custom formats in pg_dump

  4. pg_dump: Use only LZ4 frame format for compression

  5. Minor comment improvements for compress_lz4

  6. Unify buffer sizes in pg_dump compression API

  7. Improve type handling in pg_dump's compress file API

  8. Improve wording in pg_dump compression docs

  9. Fix condition in pg_dump TAP test

  10. Add LZ4 compression to pg_dump

  11. Introduce a generic pg_dump compression API

  12. Prepare pg_dump internals for additional compression methods

  13. Fix behavior with pg_restore -l and compressed dumps

  14. Add 250c8ee07ed to git-blame-ignore-revs

  15. Provide test coverage in pg_dump for default behaviors with compression

  16. Switch pg_dump to use compression specifications

  17. Refactor code parsing compression option values (-Z/--compress)

  18. meson: Add some missing env settings for tests of pg_dump and pg_verifybackup

  19. Extend TAP tests of pg_dump to test for compression with gzip

  20. Clean up some dead code in pg_dump with tar format and gzip compression

  21. Add TAP test in pg_dump with --format=tar and --compress

  22. Replace BASE_BACKUP COMPRESSION_LEVEL option with COMPRESSION_DETAIL.

  23. Refactor the pg_dump zlib code from pg_backup_custom.c to a separate file,