Currently, aggregated calculations only work with numeric vectors. *_foreach functions skip non-numeric items, which may lead to strange results. For example, count(last_foreach(/*/key)) returns 0 if there are items key on hosts with history but all are strings.

ZBXNEXT-8355 makes this limitation more pronounced because the new count() and count_foreach() filters could be used to filter string data (e.g. count(last_foreach(/*/system.uname),"regexp","ubuntu")) if vectors in aggregated calculations supported non-numerics.