As a preparation for ensuring access safety for column families
related maps, add tables_metadata, access to members of which
would be protected by rwlock.
some times we initialize a loop variable like
auto i = 0;
or
int i = 0;
but since the type of `0` is `int`, what we get is a variable of
`int` type, but later we compare it with an unsigned number, if we
compile the source code with `-Werror=sign-compare` option, the
compiler would warn at seeing this. in general, this is a false
alarm, as we are not likely to have a wrong comparison result
here. but in order to prevent issues due to the integer promotion
for comparison in other places. and to prepare for enabling
`-Werror=sign-compare`. let's use unsigned to silence this warning.
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
The definitions of virtual tables make up approximately a quarter of the
huge system_keyspace.cc file (almost 4K lines), pulling in a lot of
headers only used by them.
Move them to a separate source file to make system_keyspace.cc easier
for humans and compilers to digest.
This patch also moves the `register_virtual_tables()`,
`install_virtual_readers()` as well as the `virtual_tables` global.
Closes#14308
