Re: [PG19]pg_verifybackup never finishes on a gzip-compressed tar backup

> On Oct 6, 2026, at 09:15, shihao zhong <zhong950419(at)gmail(dot)com> wrote:
>
> Hi hackers,
>
> I used Opus to analyze the new features in PG 19.
> It found that pg_verifybackup never finishes on a tar-format
> backup taken with pg_basebackup -Ft -z.
>
> I had manually proved that by hand.
>
> On REL_19_STABLE:
>
> pg_basebackup -D /tmp/verify_targz.66809/bk -c fast -Ft -z
> pg_verifybackup /tmp/verify_targz.66809/bk
> # still running after 20 s, killing pg_waldump
> pg_verifybackup: error: WAL parsing failed for timeline 1
> pg_verifybackup -n /tmp/verify_targz.66809/bk
> backup successfully verified
> rewrite pg_wal.tar.gz as a single gzip member
> pg_verifybackup /tmp/verify_targz.66809/bk
> backup successfully verified
>
> With WAL streaming, pg_basebackup ends the gzip stream before and
> after every tar header, so pg_wal.tar.gz is a chain of gzip members.
> astreamer_gzip_decompressor_content() loops until avail_in is zero.
> After the first member inflate() keeps returning Z_STREAM_END and
> takes no more input, so the loop never ends. The loop runs in
> pg_waldump, and pg_verifybackup waits for it.
>
> Patches attached. 0001 calls inflateReset() when inflate() returns
> Z_STREAM_END, so the next member is read. 0002 adds a --gzip case to
> the tar test in 007_wal.pl and is optional.
>
> Thanks,
> Shihao
>
> <v1-0001-Handle-concatenated-gzip-members-in-astreamer-gzi.patch><v1-0002-Add-test-for-pg_verifybackup-on-a-gzip-compressed.patch>

Look like a dup of https://www.postgresql.org/message-id/5962B878-C43D-4EBC-9E95-1F945CE5E586%40gmail.com.

Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/