This replxx object is pretty heavy and in debug build may slow down [1]
(although I cannot confirm 0.5s delay for each query in debug build) the
client and besides it is not required since ClickHouse-Extras/replxx#10,
which changes the behaviour of history_save(), and now it will not
update current session anymore, only save the history to the disk.
[1]: https://github.com/ClickHouse/ClickHouse/pull/13086#issuecomment-667719026
By default replxx reload history from the file in
replxx::Replxx::history_save(), and this will overlaps current session
history with the history from other sessions, and this does not looks a
great idea (bash and other interpreters don't do this).
So to avoid this, use separate replxx::Replxx instance.
It is not easy to keep in mind that C-p/C-n is not
history-previous/history-next in replxx, thus it is pretty easy to
mistype.
Previous COMPLETE_NEXT/COMPLETE_PREV bindings has been binded to the
M-P/M-N (that was used for HISTORY_COMMON_PREFIX_SEARCH before, but it
also binded to M-p/M-n).
Plus clickhouse-client can be compiled with readline, so it is better to
make bindings the same.
