Steps to reproduce:

1. Create a calculated item prototype like:

min(last_foreach(/*/onuPonRxOpticalPower[0]?[tag="CTO:{$CTO}"]))

1. Apply the new item to the template (5k+ hosts!)

Result:
Utilization of history poller data collector processes go to 100%
Load on database increased.

Expected:
The same as any other calculated item: get it from Cache, instead of polling the database.