具有限制的Graphql-ruby分页会生成n + 1个查询

如何解决具有限制的Graphql-ruby分页会生成n + 1个查询

想象一下，您拥有某项的用户和订阅。您需要对用户的订阅进行分页。每个用户都有不同数量的订阅。这是我想到的第一件事：

users = User.where(id:[array]).index_by(&:id) # find users and make an object with id as a key
subs = Subs.where(user_id: [array]).limit(3).offset(1) # find subs for all users what we need
subs.forEach{|s| users[s[:id]].subs <<  s} # build graphql response

但是它不起作用，因为它通常限制所有用户，但我们需要每个用户。 输出应如下所示：

{
 users: [
  {
    id: 1,subs: [sub1,sub2] // this user has only two elements and it's like an end of pagination
  },{
    id: 2,subs: [sub3,sub4,sub5] // this user has more items on next page
  }
 ]
}

Graphql默认情况下为每个用户进行子查询以使其真实，但n + 1。有没有什么方法可以使它在没有n + 1的情况下并通过cpu和内存使用进行优化？

解决方法

在这里解决https://elixirforum.com/t/how-to-do-pagination-in-a-nested-graphql-query-with-dataloader-batch-load/25282也许对某人有帮助。这样的查询应该带有分区。

  def query(queryable,params) do
   case params do
      %{chapters: true,offset: offset,first: first} ->
        last = offset + first
        query = from r in queryable,select: r,select_merge: %{chapter_number: fragment("row_number() over (PARTITION by parent_id order by \"name\")")}
        from r in subquery(query),select: %Wikisource.Book{id: r.id,name: r.name,info: r.info,preface: r.preface,info_html: r.info_html,preface_html: r.preface_html},where: r.chapter_number >= ^offset and r.chapter_number < ^last
      %{order_by: order_by,offset: from,first: size} -> from record in queryable,order_by: ^order_by,offset: ^from,limit: ^size