class PrimaryGroupLookup def initialize(user_ids=[]) @user_ids = user_ids.tap(&:compact!).tap(&:uniq!).tap(&:flatten!) end # Lookup primary group for a given user id def [](user_id) users[user_id] end private def self.lookup_columns @lookup_columns ||= %i{id name flair_url flair_bg_color flair_color} end def users @users ||= user_lookup_hash end def user_lookup_hash users_with_primary_group = User.where(id: @user_ids) .where.not(primary_group_id: nil) .select(:id, :primary_group_id) group_lookup = {} group_ids = users_with_primary_group.map(&:primary_group_id).compact Group.where(id: group_ids).select(self.class.lookup_columns) .each { |g| group_lookup[g.id] = g } hash = {} users_with_primary_group.each do |u| hash[u.id] = group_lookup[u.primary_group_id] end hash end end