ActiveRecord group by count

AR_group_and_count.rb

Rental.group(:vhs).count #=>

#{<Vhs:0x00007f8d5e2bf0f0 id: 17, serial_number: "MAX-luqovgdk8e7tl", movie_id: 9 => 1,
 #<Vhs:0x00007f8d4f81a4a0 id: 29, serial_number: "BABA-t6k24krzqclts", movie_id: 13 =>2,
 #<Vhs:0x00007f8d4f854538 id: 11, serial_number: "BABA-begvxe7ai0rc6", movie_id: 13 =>3}