如何查询 mongodb 以查找包含来自另一个数组的两个元素的数组

Question

假设我在 mongo 中有以下文件：

{_id: 0, tags: ['first', 'second', 'third', fourth']},
{_id: 1, tags: ['fifth', 'seventh', 'first', second']},
{_id: 2, tags: ['eigth', 'awesometh', 'fancyth']},
{_id: 3, tags: ['fourth', 'fifteenth', 'something']},

我想从以下数组中查找包含两个或多个的文档：['first', 'second', third', 'fourth', 'fifteenth']

到目前为止，我唯一的想法是为每个组合生成一个带有子句的巨型查询，如下所示：

{$or: [
    {tags: {$in: ['first', 'second']}},
    {tags: {$in: ['second', 'third']}},
    {tags: {$in: ['first', 'third']}},
    ...etc...
  ]
}

这显然不是一个优雅的解决方案。有没有更好的办法？

Answer 1

您可以使用aggregate 管道执行此操作，该管道使用$setIntersection 查找匹配的tags，然后使用$size 对它们进行计数：

var tags = ['first', 'second', 'third', 'fourth', 'fifteenth'];
db.test.aggregate([
    // Project the original doc along with a count of the tag matches
    {$project: {
        _id: 0,
        matches: {$size: {$setIntersection: ['$tags', tags]}},
        doc: '$$ROOT'
    }},
    // Filter to just those docs with at least 2 matches
    {$match: {matches: {$gte: 2}}}
])

输出

{ "matches": 4, "doc": { "_id": 0, "tags": ["first", "second", "third", "fourth"] }}
{ "matches": 2, "doc": { "_id": 1, "tags": ["fifth", "seventh", "first", "second"] }}
{ "matches": 2, "doc": { "_id": 3, "tags": ["fourth", "fifteenth", "something"] }}