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: gkokolatos@pm.me, Tom Lane <tgl@sss.pgh.pa.us>
Cc: Michael Paquier <michael@paquier.xyz>, Andrew Dunstan <andrew@dunslane.net>, Alexander Lakhin <exclusion@gmail.com>, Justin Pryzby <pryzby@telsasoft.com>, shiy.fnst@fujitsu.com, pgsql-hackers@lists.postgresql.org, Rachel Heaton <rachelmheaton@gmail.com>
Date: 2023-05-08T18:20:42Z
Lists: pgsql-hackers 

On 5/8/23 18:19, gkokolatos@pm.me wrote:
> 
> 
> 
> 
> 
> ------- Original Message -------
> On Monday, May 8th, 2023 at 3:16 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> 
> 
>>
>>
>> I wrote:
>>
>>> Michael Paquier michael@paquier.xyz writes:
>>>
>>>> While testing this patch, I have triggered an error pointing out that
>>>> the decompression path of LZ4 is broken for table data. I can
>>>> reproduce that with a dump of the regression database, as of:
>>>> make installcheck
>>>> pg_dump --format=d --file=dump_lz4 --compress=lz4 regression
>>
>>> Ugh. Reproduced here ... so we need an open item for this.
>>
>>
>> BTW, it seems to work with --format=c.
>>
> 
> Thank you for the extra tests. It seems that exists a gap in the test
> coverage. Please find a patch attached that is addressing the issue
> and attempt to provide tests for it.
> 

Seems I'm getting messages with a delay - this is mostly the same fix I
ended up with, not realizing you already posted a fix.

I don't think we need the local "in" variable - the pointer parameter is
local in the function, so we can modify it directly (with a cast).
WriteDataToArchiveLZ4 does it that way too.

The tests are definitely a good idea. I wonder if we should add a
comment to DEFAULT_IO_BUFFER_SIZE mentioning that if we choose to
increase the value in the future, we needs to tweak the tests too to use
more data in order to exercise the buffering etc. Maybe it's obvious?


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,