Mongo - 与整个阵列完全匹配

Question

我的文件看起来像这样：

{"arr":["a","b","c"]},
{"arr":["a","b","x"]},
{"arr":["c","b","a"]},
{"arr":["a","b","c"]}

我想调用distinct来获取所有唯一数组，但是，默认情况下查询数组匹配元素，这意味着：

db.getCollection("mycoll").distinct("arr",{});

返回：

["a","b","c","x"]

而不是

[["a","b","c"],
 ["a","b","x"],
 ["c","b","a"]]

如何查询不同的数组？或者，我也希望得到每个结果的出现次数：

{["a","b","c"] : 2,
 ["a","b","x"] : 1,
 ["c","b","a"] : 1}

Answer 1

您可以在汇总管道中使用$group arr和$sum。

 db.mycoll.aggregate({$group:{_id:"$arr", count:{$sum:1}}})