Implement SUNIONSTORE volatile find keys for Ohm

find_in.rb

      def keys(hash)
        model.debug("#{model.name}.find: #{key} : #{hash}")
        [].tap do |keys|
          hash.each do |attr, values|
            # nb: String is Enumerable in 1.8.x...
            attr_type = model.types[attr]
            if !(Enumerable === values) || ( attr_type && attr_type < Enumerable && attr_type != String )
              Array(values).each do |v|
                keys << model.index_key_for(attr, v)
              end
            else
              keys << union_key_for(attr,values)
            end
          end
        end.uniq
      end
      
      def union_key_for(attr, values)
        model.debug "union_key_for: #{attr}: #{values}"
        source = values.map {|v| model.index_key_for(attr, v) }
        target = source.reduce(&:*)
        apply(:sunionstore, source.shift, source, target)
        target
      end