SNMP discovery - discarding netapp volumes based on their index value

[ivgenyr]

Hi everyone,
i have several NetApp installations which i would like to monitor ( amongst other devices).
The problem is that some of the volumes i have, are ISCSI, which means that they will appear full when monitored from the outside (SNMP).
The solution i came up with, is to monitore those volumes using ssh commands ( but that's a whole different topic).
So, at first i would like to not create items for those volumes.
If i run snmpwalk, i see that all ISCSI volumes are having SNMPINDEX of 1058..
Now, how do i add a rule to the discovery rule to not dicover those?
I managed to add a preprocessing rule to extract the snmpindex from the output using regex, but that's it...

[ivgenyr]

OK,
after doing some more digging, looks like the better option is to use Filters in the discovery rule.
The SNMP output i get looks like that:

[{"{#SNMPINDEX}":"4","{#VOLNAME}":""},
{"{#SNMPINDEX}":"1028","{#VOLNAME}":""},
{"{#SNMPINDEX}":"1034","{#VOLNAME}":"/"},
{"{#SNMPINDEX}":"1038","{#VOLNAME}":"/"},
{"{#SNMPINDEX}":"1042","{#VOLNAME}":"/labs_datastore01"}]

So what i want to do is to filter out the records where VOLNAME is empty ("").
I added a filter for macro {#VOLNAME} and regex pattern "", but it doesn't catch it. Tried also regex ^$ - same result.
Someone has an idea what am i missing here ?