Ref:
https://cwiki.apache.org/confluence/display/solr/Shards+and+Indexing+Data+in+SolrCloud
If an update specifies only the non-routed id, will SolrCloud select the
correct shard for updating?
If an update specifies a different route, will SolrCloud delete the
previous document with the same id but with the different routing? (Will
it effectively change which shard the document is stored on?)
Does the document id have to be unique ignoring the routing prefix? (Is
the routing prefix considered as part of the id for uniqueness?)
-Mike
