how to show aggregation results on Rails 4 - ruby

Question

Syntax in mongodb:
db.orders.aggregate(
{$unwind: "$lines"},
{$group :
{_id: {sku: "$lines.sku", desc: "$lines.description"},
qty : {$sum : 1}}},{ $sort : { qty : -1}}
)
I want to to show the result of the above query on Rails.
I'm using Mongoid with Rails 4 and my Gemfile:
gem 'mongoid', github: 'mongoid/mongoid'
As I understand, the only way to write the query above is to install gem for moped driver.
So, my 1st question is how that line should be declared in the Gemfile for Rails 4 and Ruby 2.0 ?
I assume the query in moped would look like:
Order.collection.aggregate(
{"$unwind" => "$lines"},
{"$group" => {"_id" => {"sku" => "$lines.sku", desc => "$lines.description"},
qty => {"$sum" => 1}}},
{ "$sort" => { "qty" => -1}})
I would like to show results of this query, by clicking a button on the index page without passing parameters.
The 2nd question is that I can't figure out how to change controller and index view page to put a button that will call this query.
UPDATE
index method part of the controller as below:
def index
#orders = if params[:search]
Order.search(params[:search]).queryable.asc(:_id).paginate(:page => params[:page], :per_page => 20)
elsif params[:search_from] && params[:search_to]
Order.search_date(params[:search_from], params[:search_to]).queryable.asc(:_id).paginate(:page => params[:page], :per_page => 20)
else
Order.shipping_today(Date.today, Date.today).queryable.asc(:_id).paginate(:page => params[:page], :per_page => 20)
end
index.html.erb:
<h1>Date: <%= Date.today %></h1>
<%= form_tag orders_path, :method => 'get' do %>
<p>Order date range:<br>
<%= text_field_tag :search_from, params[:search_from] %> - <%= text_field_tag :search_to, params[:search_to] %>
<%= submit_tag "Search", :name => nil %>
</p>
<% end %>
<%= form_tag orders_path, :method => 'get' do %>
<p>
<%= text_field_tag :search, params[:search] %>
<%= submit_tag "Search", :name => nil %>
<%= link_to "Reset", orders_path %>
</p>
<% end %>
<%= form_tag orders_path, :method => 'get' do %>
<p>
<%= submit_tag "Statistics", :name => nil %>
</p>
<% end %>
<div class="digg_pagination">
<div class="page_info">
<%= page_entries_info #orders %>
</div>
<%= will_paginate #orders, :container => false %>
</div>
<br />
<table border = 1 >
<thead>
<tr>
<th>Shipping date</th>
<th>Order #</th>
<th>Ship to name</th>
<th>Tracking #</th>
<th>Shipped</th>
<th>Action</th>
<th></th>
</tr>
</thead>
<tbody>
<% #orders.each do |order| %>
<tr>
<td><%= order.shipping_date %></td>
<td><%= link_to order.order_number, order_path(order) %></td>
<td><%= order.ship_to_fname %></td>
<td><%= order.track_num %></td>
<td><%= order.ship_date %></td>
<td><%= link_to 'Edit', edit_order_path(order) %></td>
<td><%= link_to 'New', new_order_path(order) %></td>
<td><%= link_to 'Destroy', order, method: :delete, data: { confirm: 'Are you sure?' } %></td>
</tr>
<% end %>
</tbody>
</table>
<br />
<%= link_to 'New Order', new_order_path %>

Answer 1

The line in Gemfile that you wrote gem 'mongoid', github: 'mongoid/mongoid' should be enough for that query to work.
After aggregate commant you'll get an array with the result of the aggregation.
You can assign it to the instance variable in the controller and iterate on it in view.
For example:
# LinesController
def index
#lines = Order.collection.aggregate(
{"$unwind" => "$lines"},
{"$group" => {"_id" => {"sku" => "$lines.sku", desc => "$lines.description"},
qty => {"$sum" => 1}}},
{ "$sort" => { "qty" => -1}})
end
# lines/index.html.erb
<ul>
<% #lines.each do |line| %>
<li>
<b><%= line['_id']['sku'] %></b>
<%= line['qty'] %>
</li>
<% end %>
</ul>