LazyQueriesProblem.rb

@users = User.where(:page_owner         => true).order("updated_at DESC").limit(100) if params[:page_owner]
@users = User.where(:page_owner_request => true}.order("updated_at DESC").limit(100) if params[:page_owner_request]
@users = User.where(:deleted            => true}.order("updated_at DESC").limit(100) if params[:deleted]
@users = @users || User.all

LazyQueriesSolution.rb

@users = User.order("updated_at DESC").limit(100)
@users = @users.where(:page_owner         => true) if params[:page_owner]
@users = @users.where(:page_owner_request => true) if params[:page_owner_request]
@users = @users.where(:deleted            => true) if params[:deleted]