map_reduce_cf() is called with varying template parameters which each
have to be compiled separately. Unifying the internals to use types based
on std::any reduced the object size by 15% (115MB->99MB) with presumably
a commensurate decrease in compile time.
A version that used "I" instead of "std::any" (and thus merged the
internals only for callers that used the same result type) delivered
a 10% decrease in object size. While std::any is less safe, in this
case it is completely encapsulated.
Message-Id: <20180402213732.432-1-avi@scylladb.com>
cadd983856