this is follow-up from ZBX-4363

Without such default limit this method is potential performance killer.

Maybe the "limit" parameter should be required but not the optional?

If it missing I suggest the default limit = 1000
or a limit taken form global frontend configuration option "Search/Filter elements limit" <- it used at the moment in history of latest data page.

To discard any limits an user could specify "limit":0

Optionally:
if the limit is reached then we could return additional field in result which will inform user that there are additional values for requested period - see ZBX-3296