Trigger question, is compare on non existing previous item value possible?

[toj]

Hi

Im trying to trigger if the previous item value is not the same as "current/last" item value, but trigger only fires if there is a item value in history aka if a previous item value exists.
In my world a item value that does not exists should not be equal to one that does, is what im trying to do just not possible in zabbix?

# My Trigger
count(/Zabbix server/log[/var/log/my.log],#1,"regexp","ERROR")>0 and last(/Zabbix server/log[/var/log/my.log],#1)<>last(/Zabbix server/log[/var/log/my.log],#2)

// Torben

[cyber]

How long you keep history, so you end up having no more than one value there?
Otherwise its quite understandable, that you cannot make proper calculation if some values are unknown... There are some cases, where it works, but not in this case, I think...

https://www.zabbix.com/documentation/current/en/manual/config/triggers/expression#expressions-with-unknown-operands

[cyber]

How long you keep history, so you end up having no more than one value there?
Otherwise its quite understandable, that you cannot make proper calculation if some values are unknown... There are some cases, where it works, but not in this case, I think...

https://www.zabbix.com/documentation/current/en/manual/config/triggers/expression#expressions-with-unknown-operands

[toj]

Ok, that ofc. makes sense.

Thanks a lot for the anwser.