在MongoDB中查找文档，该文档的数组字段是查询数组的子集 [英] Find Documents in MongoDB whose with an array field is a subset of a query array

问题描述

假设我插入了一组文档，每个文档都有一个array字段.我想找到所有文档，使它们的array字段是查询数组的子集.例如，如果我有以下文档，

Suppose I have a insert a set of documents each with an array field. I would like to find all documents such that their array field is a subset of a query array. For example, if I have the following documents,

collection.insert([
  {
     'name': 'one',
     'array': ['a', 'b', 'c']
  },
  {
     'name': 'two',
     'array': ['b', 'c', 'd']
  },
  {
     'name': 'three',
     'array': ['b', 'c']
  }
])

并且我查询collection.find({'array': {'$superset': ['a', 'b', 'c']})，我希望看到文档one和three，因为['a', 'b', 'c']和['b', 'c']都是['a', 'b', 'c']的子集.换句话说，我想做Mongo $all查询的反函数，该查询选择所有文档，以便查询数组是文档array字段的子集.这可能吗?如果可以，怎么办?

and I query collection.find({'array': {'$superset': ['a', 'b', 'c']}), I would expect to see documents one and three as ['a', 'b', 'c'] and ['b', 'c'] are both subsets of ['a', 'b', 'c']. In other words, I'd like to do the inverse of Mongo's $all query, which selects all documents such that the query array is a subset of the document's array field. Is this possible? and if so, how?

推荐答案

有一种简单的方法可以通过聚合框架或查找查询来实现.

There is a simple way to do this with aggregation framework or with a find query.

查找查询很简单，但是您必须使用$ elemMatch运算符:

Find query is simple, but you have to use $elemMatch operator:

> db.collection.find({array:{$not:{$elemMatch:{$nin:['a','b','c']}}}}, {_id:0,name:1})

请注意，这表明我们不希望匹配一个数组，该数组的元素(同时)不等于"a"，"b"或"c".我添加了一个投影，该投影仅返回结果文档的名称字段，该字段是可选的.

Note that this indicates that we want to not match an array which has an element which is (at the same time) not equal to 'a', 'b' or 'c'. I added a projection which only returns the name field of the resultant document which is optional.

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