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I am using rails 3 with mongoid. I have a collection of Stocks with an embedded collection of Prices : class Stock include Mongoid::Document field :name, :type => String field :code, :type => Integer embeds_many :prices class Price include Mongoid::Document field :date, :type => DateTime field :value, :type => Float embedded_in :stock, :inverse_of => :prices I would like to get the stocks whose the minimum price since a given date is lower than a given price p, and then be able to sort the prices for each stock. But it looks like Mongodb does not allow to do it. Because this will not work: @stocks = Stock.Where(:prices.value.lt => p) Also, it seems that mongoDB can not sort embedded objects. So, is there an alternative in order to accomplish this task ? Maybe i should put everything in one collection so that i could easily run the following query: @stocks = Stock.Where(:prices.lt => p) But i really want to get results grouped by stock names after my query (distinct stocks with an array of ordered prices for example). I have heard about map/reduce with the group function but i am not sure how to use it correctly with Mongoid. http://www.mongodb.org/display/DOCS/Aggregation The equivalent in SQL would be something like this: SELECT name, code, min(price) from Stock WHERE price<p GROUP BY name, code Thanks for your help.

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