watched_user_blog_ids=Blog.select("id").where("author_id in #{user_ids}").count==0?"-1":Blog.select("id").where("author_id in #{user_ids}").map{|blog|blog.id}.join(",")
watched_user_blog_ids=Blog.select("id").where("author_id in #{user_ids}").count==0?"":Blog.select("id").where("author_id in #{user_ids}").map{|blog|blog.id}.join(",")