It’s now possible to associate routing values with aliases. This feature can be used together with filtering aliases in order to avoid unnecessary shard operations.

The following command creates a new alias "alias1" that points to index "test". After "alias1" is created, all operations with this alias are automatically modified to use value "1" for routing.

$ curl -XPOST 'http://localhost:9200/_aliases' -d '
{
    "actions" : [
        {
            "add" : {
                 "index" : "test",
                 "alias" : "alias1",
                 "routing" : "1"
            }
        }
    ]
}'

It’s also possible to specify different routing values for searching and indexing operations:

$ curl -XPOST 'http://localhost:9200/_aliases' -d '
{
    "actions" : [
        {
            "add" : {
                 "index" : "test",
                 "alias" : "alias2",
                 "search-routing" : "1,2",
                 "index-routing" : "2"
            }
        }
    ]
}'

As shown in the example above, search routing may contain several values separated by comma. Index routing can contain only a single value.

If an operation that uses routing alias also has a routing parameter, an intersection of both alias routing and routing specified in the parameter is used. For example the following command will use "2" as a routing value:

$ curl -XGET 'http://localhost:9200/alias2/_search?q=user:kimchy&routing=2,3'