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>, shiy.fnst@fujitsu.com, pgsql-hackers@lists.postgresql.org, Rachel Heaton <rachelmheaton@gmail.com>
Date: 2023-02-25T14:05:53Z
Lists: pgsql-hackers

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On Fri, Feb 24, 2023 at 11:02:14PM -0600, Justin Pryzby wrote:
> I have some fixes (attached) and questions while polishing the patch for
> zstd compression.  The fixes are small and could be integrated with the
> patch for zstd, but could be applied independently.

One more - WriteDataToArchiveGzip() says:

+       if (cs->compression_spec.level == 0)
+           pg_fatal("requested to compress the archive yet no level was specified");

That was added at e9960732a.  

But if you specify gzip:0, the compression level is already enforced by
validate_compress_specification(), before hitting gzip.c:

| pg_dump: error: invalid compression specification: compression algorithm "gzip" expects a compression level between 1 and 9 (default at -1)

5e73a6048 intended that to work as before, and you *can* specify -Z0:

    The change is backward-compatible, hence specifying only an integer
    leads to no compression for a level of 0 and gzip compression when the
    level is greater than 0.

    $ time ./src/bin/pg_dump/pg_dump -h /tmp regression -t int8_tbl -Fp --compress 0 |file -
    /dev/stdin: ASCII text

Right now, I think that pg_fatal in gzip.c is dead code - that was first
added in the patch version sent on 21 Dec 2022.

-- 
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,