We have a Zabbix environment that we migrated from version 3.0.5 to 4.2.2.

 Just after the migration we noticed a very different behavior in housekeeper, it started running for almost 4 hours and we detected that not all history and trends data was being deleted.

 Our approach to the problem was:

1) We stopped housekeeper and deleted data by manually;

2) We started housekeeper only for history and it started running for about 20/25 minutes and deleting all data needed.

3) We started housekeeper for history + trends and we had the same issue, housekeeping running almost 4 hours.

We found that after housekeeper starts it stays for almost 3 hours running this query: "select itemid,min(clock) from trends group by itemid"

After that query completes it starts deleting. We decided to disable housekeeper from trends and doing it manually. Is this is a known issue?  

Note:

we have some partitioned tables on our MariaDB Zabbix Database:

'trends','trends_uint','history','history_uint','history_str'