Horton

Re: Add LZ4 compression in pg_dump

Justin Pryzby <pryzby@telsasoft.com>

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From: Justin Pryzby <pryzby@telsasoft.com>
To: Michael Paquier <michael@paquier.xyz>
Cc: Tomas Vondra <tomas.vondra@enterprisedb.com>, gkokolatos@pm.me, shiy.fnst@fujitsu.com, pgsql-hackers@lists.postgresql.org, Rachel Heaton <rachelmheaton@gmail.com>
Date: 2023-04-12T22:52:40Z
Lists: pgsql-hackers 
On Thu, Apr 13, 2023 at 07:23:48AM +0900, Michael Paquier wrote:
> On Tue, Apr 11, 2023 at 08:19:59PM -0500, Justin Pryzby wrote:
> > On Wed, Apr 12, 2023 at 10:07:08AM +0900, Michael Paquier wrote:
> >> Yes, this comment gives no value as it stands.  I would be tempted to
> >> follow the suggestion to group the whole code block in a single ifdef,
> >> including the check, and remove this comment.  Like the attached
> >> perhaps?
> > 
> > +1
> 
> Let me try this one again, as the previous patch would cause a warning
> under --without:-zlib as user_compression_defined would be unused.  We
> could do something like the attached instead.  It means doing twice
> parse_compress_specification() for the non-zlib path, still we are
> already doing so for the zlib path.
> 
> If there are other ideas, feel free.

I don't think you need to call parse_compress_specification(NONE).
As you wrote it, if zlib is unavailable, there's no parse(NONE) call,
even for directory and custom formats.  And there's no parse(NONE) call
for plan format when zlib is available.

The old way had preprocessor #if around both the "if" and "else" - is
that what you meant ?

If you don't insist on calling parse(NONE), the only change is to remove
the empty #else, which was my original patch.

"if no compression specification has been specified" is redundant with
"by default", and causes "not the others" to dangle.

If I were to rewrite the comment, it'd say:

+        * When gzip is available, custom and directory formats are compressed by
+        * default

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,