pg_restore -l has always been able to read the TOC data of a dump even
if its binary has no support for compression, for both compressed and
uncompressed dumps.
5e73a60 has introduced a backward-incompatible
behavior by switching a warning to a hard error in the code path reading
the header data of a dump, preventing the TOC items to be listed even if
pg_restore -l, with no support for compression, is used on a compressed
dump. Most modern systems should have support for zlib, but it can be
also possible that somebody relies on the past behavior when copying
over a dump where binaries are not built with zlib support (most likely
some WIN32 flavors these days, though most environments should provide
that).
There is no easy way to have a regression test for this pattern, as it
requires a mix of dump/restore commands with different compilation
options, with and without compression. One possibility I see here would
be to have a command-line option that enforces a non-compression check
for a build that supports compression, but that does not seem worth the
cost, either.
Reported-by: Justin Pryzby
Author: Georgios Kokolatos
Discussion: https://postgr.es/m/
20230125180020.GF22427@telsasoft.com