Question

I don’t fully understand what rails scopes do. The rails query:

UserDesign.joins(:order_line_items)
     .where('order_line_items.created_at > ?',Date.today-1.month)
     .find(:all,
           :select=>'order_line_items.design_id as id,sum(order_line_items.quantity) as quantity',
           :group=>'order_line_items.design_id',
           :order=>'quantity desc'
     )

Returns the items:

 UserDesign Load (0.8ms)  SELECT order_line_items.design_id as id,sum(order_line_items.quantity) as quantity FROM "user_designs" INNER JOIN "order_line_items" ON "order_line_items"."design_id" = "user_designs"."id" WHERE (order_line_items.created_at > '2012-11-12') GROUP BY order_line_items.design_id ORDER BY quantity desc
+-----+----------+
| id  | quantity |
+-----+----------+
| 199 | 65       |
| 196 | 31       |
| 197 | 31       |
| 198 | 30       |
| 204 | 30       |
| 203 | 30       |
+-----+----------+

This is correct, but only two columns are included. The same query as a named scope yields:

UserDesign Load (0.7ms)  SELECT order_line_items.design_id as id,sum(order_line_items.quantity) as quantity FROM "user_designs" INNER JOIN "order_line_items" ON "order_line_items"."design_id" = "user_designs"."id" WHERE (order_line_items.created_at > '2012-11-12') GROUP BY order_line_items.design_id ORDER BY quantity desc
UserDesign Load (1.0ms)  SELECT "user_designs".* FROM "user_designs" 
+-----+-------+---
| id  | de... |...
+-----+-------+---
| 196 | aa... |...
| 199 | fd... |...
| 198 | as... |...
| 197 | as... |...
| 203 | Test  |...
| 204 | My... |...
+-----+-------+---

The SQL query is identical and all columns are returned, but they are not in the correct order. I would like to either

1. Use a named scope that is ordered correctly
2. wrap the plain query in a function but return all columns

Thanks!

EDIT:

For completeness, here’s the named scope:

scope :popular_this_month, lambda{
     joins(:order_line_items)
     .where('order_line_items.created_at > ?',Date.today-1.month)
     .find(:all,
           :select=>'order_line_items.design_id as id,sum(order_line_items.quantity) as quantity',
           :group=>'order_line_items.design_id',
           :order=>'quantity desc'
     )}

Answer 1

In the first case you’re passing a select option specifiying those 2 columns, so those two columns are what is returned. If you want more columns, list them (You can use table_name.* to get all the columns for a table)

In your second case you’re calling find inside your named scope, which doesn’t make any sense – a named scope is just a set of conditions and options, you shouldn’t be actually doing the find in there. I suspect in that case it’s ignoring all the options you’re passing to find.

You want something more along the lines of

scope :popular_this_month, lambda{
     joins(:order_line_items).
     where('order_line_items.created_at > ?',Date.today-1.month).
     select(...).
     order(...).
     group(...)}

which should result as the same behaviour as the first example.