ruby on rails - Using `count` with scopes that have a select method -

i have scope --

scope :most_stock, -> {     joins(:stock_keeping_units).     select("items.*, count(stock_keeping_units.id) stock_keeping_unit_count").     group('items.id').     order('stock_keeping_unit_count desc').     where('stock_keeping_units.sold = false') } 

when run item.most_stock, works fine , dandy.

however, when run item.most_stock.count, following error -

pg::syntaxerror: error: syntax error @ or near "as" line 1

the generated sql query -

select count(items.*, count(stock_keeping_units.id) stock_keeping_unit_count) count_items_all_count_stock_keeping_units_id_as_stock_keeping_u, items.id items_id "items" inner join "stock_keeping_units" on "stock_keeping_units"."item_id" = "items"."id" , "stock_keeping_units"."deleted_at" null "items"."deleted_at" null , (stock_keeping_units.sold = false) group items.id order stock_keeping_unit_count desc

a work around use length

i'm curious know count didn't work here or should ideally work?