检查数组中的每个元素是否符合条件 [英] Check if every element in array matches condition

问题描述

我有一组文档:

date: Date
users: [
  { user: 1, group: 1 }
  { user: 5, group: 2 }
]

date: Date
users: [
  { user: 1, group: 1 }
  { user: 3, group: 2 }
]

我想对该集合进行查询，以查找我的用户数组中的每个用户 ID 都在另一个数组 [1, 5, 7] 中的所有文档.在这个例子中，只有第一个文档匹配.

I would like to query against this collection to find all documents where every user id in my array of users is in another array, [1, 5, 7]. In this example, only the first document matches.

我能找到的最佳解决方案是:

The best solution I've been able to find is to do:

$where: function() { 
  var ids = [1, 5, 7];
  return this.users.every(function(u) { 
    return ids.indexOf(u.user) !== -1;
  });
}

不幸的是，这似乎会影响性能，$where 文档中有说明:

Unfortunately, this seems to hurt performance is stated in the $where docs:

$where 评估 JavaScript，不能利用索引.

$where evaluates JavaScript and cannot take advantage of indexes.

如何改进此查询?

推荐答案

你想要的查询是这样的:

The query you want is this:

db.collection.find({"users":{"$not":{"$elemMatch":{"user":{$nin:[1,5,7]}}}}})

这表示找到所有不包含列表 1、5、7 之外元素的文档.

This says find me all documents that don't have elements that are outside of the list 1,5,7.

这篇关于检查数组中的每个元素是否符合条件的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！