What happens when a streaming expression is sent to an alias

[Ufuk YILMAZ]

When you send an expression to an alias named "myAlias" pointing to N 
number of collections, each having M number of replicas, how does it 
work? Is the same expression executed in all of the NxM machines at the 
same time? Or a random node is selected from the NxM replica's nodes? Or 
something else?

curl -L -X POST 'http://node1:8983/solr/myAlias/stream' -H 
'Content-Type: application/x-www-form-urlencoded' --data-urlencode 
'expr=echo(1)'