mongodb - Mongo filter results by distinct field -

mongodb - Mongo filter results by distinct field -

i utilize ruby driver mongo : https://github.com/mongodb/mongo-ruby-driver

i have many documents in collection :

{ "_productid" => 10 .... } { "_productid" => 10 .... } { "_productid" => 12 .... }

what request documents distinct "_productid", mean want take first , lastly collection item in exemple.

@db['collection'].distinct('_productid')

http://docs.mongodb.org/manual/reference/method/db.collection.distinct/

http://wiki.summercode.com/mongodb_aggregation_functions_and_ruby_counting_and_grouping

mongodb