Mpdreamz/NEST — pull request #391 by jjherbst (2013-11-19 19:16:56+00:00)
Title: Added ExecuteOnPrimaryFirst read preference.

Added another read preference; "_primary_first"
"The operation will go and be executed on the primary shard, and if not available (failover), will execute on other shards."

http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/search-request-preference.html