How do I update a nested array in an existing elasticsearch document with logstash? -

How do I update a nested array in an existing elasticsearch document with logstash? -

let's have existing document in next index

visitors-20150412

{ "_index" : "visitors-20150412", "_type" : "visitor", "_id" : "62df20c58f008fea", "_source" : { "id" : "62df20c58f008fea", "ip" : "123.456.789.0", "referrer" : "google", "pages" : [] }

and have log of "pages" visitor went want logstash read through , add together "pages" array. page document might this:

{ "visitorid" : "62df20c58f008fea", "url" : "http://www.example.com/whatever", "title" : "page title" }

how setup logstash configuration file append "page" original visitors document _id "62df20c58f008fea"?

elasticsearch logstash