在MongoDB中搜索数组并按匹配数排序 [英] In MongoDB search in an array and sort by number of matches

问题描述

问题是下一个:

获取带有标签的文档列表，按比赛总数排序

但是他们说使用Aggregation Framework可以实现，有可能吗?

But they say that is possible using Aggregation Framework, it's possible?

推荐答案

是的，可以使用Aggregation Framework.

Yes, it's possible using Aggregation Framework.

假设

• 此处使用的数据集与

• The dataset used here is the same used in Get documents with tags in list, ordered by total number of matches
• tags attribute is a set (no repeated elements)

查询

这种方法迫使您取消结果，并用未结束的结果重新评估匹配谓词，因此它的效率很低.

This approach forces you to unwind the results and reevaluate the match predicate with unwinded results, so its really inefficient.

db.test_col.aggregate(
    {$match: {tags: {$in: ["shirt","cotton","black"]}}}, 
    {$unwind: "$tags"}, 
    {$match: {tags: {$in: ["shirt","cotton","black"]}}}, 
    {$group: {
        _id:{"_id":1}, 
        matches:{$sum:1}
    }}, 
    {$sort:{matches:-1}}
);

预期结果

{
    "result" : [
        {
            "_id" : {
                "_id" : ObjectId("5051f1786a64bd2c54918b26")
            },
            "matches" : 3
        },
        {
            "_id" : {
                "_id" : ObjectId("5051f1726a64bd2c54918b24")
            },
            "matches" : 2
        },
        {
            "_id" : {
                "_id" : ObjectId("5051f1756a64bd2c54918b25")
            },
            "matches" : 1
        }
    ],
    "ok" : 1
}

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