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Re: pg_waldump: support decoding of WAL inside tarfile

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Thomas Munro <thomas.munro@gmail.com>
Cc: Tomas Vondra <tomas@vondra.me>, Andres Freund <andres@anarazel.de>, Michael Paquier <michael@paquier.xyz>, Andrew Dunstan <andrew@dunslane.net>, Amul Sul <sulamul@gmail.com>, Zsolt Parragi <zsolt.parragi@percona.com>, Robert Haas <robertmhaas@gmail.com>, Chao Li <li.evan.chao@gmail.com>, Anthonin Bonnefoy <anthonin.bonnefoy@datadoghq.com>, Fujii Masao <masao.fujii@gmail.com>, Jakub Wartak <jakub.wartak@enterprisedb.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2026-04-03T01:11:22Z
Lists: pgsql-hackers 
Thomas Munro <thomas.munro@gmail.com> writes:
> Thanks.  I'll go ahead and push v2 shortly, which includes Sami's
> change (with credit), unless you have any better ideas for that bit.

Not really.  I wondered for a bit if it was smart to create tar files
whose contents would appear root-owned, but it could only matter if
somebody extracted such a file as root, and I don't see a plausible
pathway for that to happen, since these are merely transient test
files.

We could dodge that hazard by using, say, "--owner=1" but I'm
not sure whether that'd introduce its own problems.  In any case,
walmethods.c's tar_open_for_write is already filling in zeroes
there.

			regards, tom lane

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Use size_t instead of Size in pg_waldump

  2. More tar portability adjustments.

  3. Further harden tests that might use not-so-compatible tar versions.

  4. Harden astreamer tar parsing logic against archives it can't handle.

  5. Fix pg_waldump/t/001_basic.pl with BSD tar on ZFS.

  6. Remove a low-value, high-risk optimization in pg_waldump.

  7. Fix misuse of simplehash.h hash operations in pg_waldump.

  8. Fix file descriptor leakages in pg_waldump.

  9. Fix poorly-sized buffers in astreamer compression modules.

  10. Remove read_archive_file()'s "count" parameter.

  11. Report detailed errors from XLogFindNextRecord() failures.

  12. Fix assorted bugs in archive_waldump.c.

  13. Remove nonfunctional tar file trailer size check.

  14. Fix finalization of decompressor astreamers.

  15. Move tar detection and compression logic to common.

  16. pg_verifybackup: Enable WAL parsing for tar-format backups

  17. pg_waldump: Add support for reading WAL from tar archives

  18. pg_waldump: Preparatory refactoring for tar archive WAL decoding.

  19. pg_waldump: Remove file-level global WalSegSz.

  20. pg_verifybackup: Verify tar-format backups.