ESA 'Group by' issue

[lukaszczerwonka]

I have 2 events with alias_host array meta as below.

Event1: "alias.host":["google.com","outlook.com","bing.com"]

Event2: "alias.host":["msn.com","google.com","microsoft.com"]

Anyone have tip how to group by alias_host in ESA EPL rule? How to compare each one separately? In this example it should be grupped by google.com