Horton

Re: Add LZ4 compression in pg_dump

gkokolatos@pm.me

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From: gkokolatos@pm.me
To: Michael Paquier <michael@paquier.xyz>
Cc: Justin Pryzby <pryzby@telsasoft.com>, pgsql-hackers@lists.postgresql.org, Rachel Heaton <rachelmheaton@gmail.com>
Date: 2022-12-05T12:48:28Z
Lists: pgsql-hackers

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------- Original Message -------
On Monday, December 5th, 2022 at 8:05 AM, Michael Paquier <michael@paquier.xyz> wrote:


> 
> 
> On Sat, Dec 03, 2022 at 11:45:30AM +0900, Michael Paquier wrote:
> 
> > While this is correct in checking that the contents are compressed
> > under --with-zlib, this also removes the coverage where we make sure
> > that this command is able to complete under --without-zlib without
> > compressing any of the table data files. Hence my point from
> > upthread: this test had better not use compile_option, but change
> > glob_pattern depending on if the build uses zlib or not.
> 
> In short, I mean something like the attached. I have named the flag
> content_patterns, and switched it to an array so as we can check that
> toc.dat is always uncompression and that the other data files are
> always uncompressed.

I see. This approach is much better than my proposal, thanks. If you
allow me, I find 'content_patterns' to be slightly ambiguous. While is
true that it refers to the contents of a directory, it is not the
contents of the dump that it is examining. I took the liberty of proposing
an alternative name in the attached v16.

I also took the liberty of applying the test pattern when it the dump
is explicitly compressed.

> > In order to check this behavior with defaults_custom_format, perhaps
> > we could just remove the -Z6 from it or add an extra command for its
> > default behavior?
> 
> This is slightly more complicated as there is just one file generated
> for the compression and non-compression cases, so I have let that as
> it is now.

I was thinking a bit more about this. I think that we can use the list
TOC option of pg_restore. This option will first print out the header
info which contains the compression. Perl utils already support to 
parse the generated output of a command. Please find an attempt to do
so in the attached. The benefits of having some testing for this case
become a bit more obvious in 0004 of the patchset, when lz4 is
introduced.

Cheers,
//Georgios

> --
> Michael

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,