in 7952200c, we changed the `selected_format` from `mc` to `me`,
but to be backward compatible the cluster starts with "md", so
when the nodes in cluster agree on the "ME_SSTABLE_FORMAT" feature,
the format selector believes that the node is already using "ME",
which is specified by `_selected_format`. even it is actually still
using "md", which is specified by `sstable_manager::_format`, as
changed by 54d49c04. as explained above, it was specified to "md"
in hope to be backward compatible when upgrading from an existign
installation which might be still using "md". but after a second
thought, since we are able to read sstables persisted with older
formats, this concern is not valid.
in other words, 7952200c introduced a regression which changed the
"default" sstable format from `me` to `md`.
to address this, we just change `sstable_manager::_format` to "me",
so that all sstables are created using "me" format.
a test is added accordingly.
Fixes#18995
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Closesscylladb/scylladb#19293
c429a8d8ae