app/models/search_term_occurrence.rb
class SearchTermOccurrence < ApplicationRecord
belongs_to :search_term, optional: true
validates_presence_of :search_term
attr_accessible :search_term, :created_at, :total, :indexed
EXPIRATION_TIME = 1.year
scope :valid, -> { where "search_term_occurrences.created_at > ?", DateTime.now - EXPIRATION_TIME }
end