Horton

Re: Add LZ4 compression in pg_dump

Tomas Vondra <tomas.vondra@enterprisedb.com>

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From: Tomas Vondra <tomas.vondra@enterprisedb.com>
To: Justin Pryzby <pryzby@telsasoft.com>
Cc: gkokolatos@pm.me, shiy.fnst@fujitsu.com, Michael Paquier <michael@paquier.xyz>, pgsql-hackers@lists.postgresql.org, Rachel Heaton <rachelmheaton@gmail.com>
Date: 2023-03-17T02:02:22Z
Lists: pgsql-hackers 

On 3/16/23 23:58, Justin Pryzby wrote:
> On Thu, Mar 16, 2023 at 11:30:50PM +0100, Tomas Vondra wrote:
>> On 3/16/23 01:20, Justin Pryzby wrote:
>>> But try reading the diff while looking for the cause of a bug.  It's the
>>> difference between reading 50, two-line changes, and reading a hunk that
>>> replaces 100 lines with a different 100 lines, with empty/unrelated
>>> lines randomly thrown in as context.
>>
>> I don't know, maybe I'm doing something wrong or maybe I just am bad at
>> looking at diffs, but if I apply the patch you submitted on 8/3 and do
>> the git-diff above (output attached), it seems pretty incomprehensible
>> to me :-( I don't see 50 two-line changes (I certainly wouldn't be able
>> to identify the root cause of the bug based on that).
> 
> It's true that most of the diff is still incomprehensible...
> 
> But look at the part relevant to the "empty-data" bug:
> 

Well, yeah. If you know where to look, and if you squint just the right
way, then you can see any bug. I don't think I'd be able to spot the bug
in the diff unless I knew in advance what the bug is.

That being said, I don't object to moving the function etc. Unless there
are alternative ideas how to fix the empty-data issue, I'll get this
committed after playing with it a bit more.


regards

-- 
Tomas Vondra
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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,