Horton

Re: Add LZ4 compression in pg_dump

Alexander Law <exclusion@gmail.com>

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From: Alexander Lakhin <exclusion@gmail.com>
To: gkokolatos@pm.me
Cc: Tomas Vondra <tomas.vondra@enterprisedb.com>, "shiy.fnst@fujitsu.com" <shiy.fnst@fujitsu.com>, Michael Paquier <michael@paquier.xyz>, Justin Pryzby <pryzby@telsasoft.com>, "pgsql-hackers@lists.postgresql.org" <pgsql-hackers@lists.postgresql.org>, Rachel Heaton <rachelmheaton@gmail.com>
Date: 2023-03-11T18:00:00Z
Lists: pgsql-hackers 
Hi Georgios,

11.03.2023 13:50, gkokolatos@pm.me wrote:
> I can not answer about the buildfarms. Do you think that adding an explicit
> check for this warning in meson would help? I am a bit uncertain as I think
> that type-limits are included in extra.
>
> @@ -1748,6 +1748,7 @@ common_warning_flags = [
>     '-Wshadow=compatible-local',
>     # This was included in -Wall/-Wformat in older GCC versions
>     '-Wformat-security',
> +  '-Wtype-limits',
>   ]
I'm not sure that I can promote additional checks (or determine where
to put them), but if some patch introduces a warning of a type that wasn't
present before, I think it's worth to eliminate the warning (if it is
sensible) to keep the source code check baseline at the same level
or even lift it up gradually.
I've also found that the same commit introduced a single instance of
the analyzer-possible-null-argument warning:
CPPFLAGS="-Og -fanalyzer -Wno-analyzer-malloc-leak -Wno-analyzer-file-leak 
-Wno-analyzer-null-dereference -Wno-analyzer-shift-count-overflow 
-Wno-analyzer-free-of-non-heap -Wno-analyzer-null-argument 
-Wno-analyzer-double-free -Wanalyzer-possible-null-argument" ./configure 
--with-lz4 -q && make -s -j8
compress_io.c: In function ‘hasSuffix’:
compress_io.c:158:47: warning: use of possibly-NULL ‘filename’ where non-null 
expected [CWE-690] [-Wanalyzer-possible-null-argument]
   158 |         int                     filenamelen = strlen(filename);
       | ^~~~~~~~~~~~~~~~
   ‘InitDiscoverCompressFileHandle’: events 1-3
...

(I use gcc-11.3.)
As I can see, many existing uses of strdup() are followed by a check for
null result, so maybe it's a common practice and a similar check should
be added in InitDiscoverCompressFileHandle().
(There also a couple of other warnings introduced with the lz4 compression
patches, but those ones are not unique, so I maybe they aren't worth fixing.)

>> It is a good thing that the restore fails with bad input. Yet it should
>> have failed earlier. The attached makes certain it does fail earlier.
>>
Thanks! Your patch definitely fixes the issue.

Best regards,
Alexander

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,