如何在MongoDB中检索对象内部的不同键 [英] How to retrieve distinct keys inside an object in MongoDB

问题描述

我在MongoDB中拥有这个:

I have this in MongoDB:

{ "_id" : ObjectId("58fb35531eb5df245d5d434f"), "name" : "d1.html", "indexation" : { "Citroen" : 1, "color" : 1, "Marca" : 1, "rojo" : 1 } }
{ "_id" : ObjectId("58fb35531eb5df245d5d4350"), "name" : "d2.html", "indexation" : { "blancos" : 1, "ocasión" : 1, "Madrid" : 1, "Coches" : 1, "rojo" : 1, "coches" : 1 } }
{ "_id" : ObjectId("58fb35531eb5df245d5d4351"), "name" : "d3.html", "indexation" : { "rojos" : 1, "Ocasión" : 1, "marcas" : 1, "Madrid" : 1, "blancas" : 1, "autos" : 1, "de" : 1 } }

您可以看到包含以上内容的图像:

You can see an image containing the above:

我想在每个文档的索引"对象中获取不同的键. 我想要得到的结果是:["Citroen", "color", "Marca", "rojo", "blancos", "ocasión", "Madrid", "Coches", "coches", "rojos", "Ocasión", "marcas", "blancas" "autos", "de"].

And I would like to get the distinct keys inside the object "indexation" in each document. The result I woul like to get is: ["Citroen", "color", "Marca", "rojo", "blancos", "ocasión", "Madrid", "Coches", "coches", "rojos", "Ocasión", "marcas", "blancas" "autos", "de"].

我正在尝试使用不同的(索引")，但是我得到了整个索引...

I'm trying with distinct ("indexation") but I get the whole indexation...

能否请您解释一下我要得到我想要的东西怎么办?

Could you explain to me what do I have to do to get what I want, please?

推荐答案

您可以使用新的 $ 3.4.4 中的objectToArrray 版本以转换所有键&值对放入文档数组，后跟$unwind& $group和$addToSet以获得不同的键

You can use new $objectToArrray in 3.4.4 version to convert all key & value pair into document arrays followed by $unwind & $group with $addToSet to get distinct keys

db.collection.aggregate([{$project: {indexation: {$objectToArray: "$indexation"}}}, {$unwind:"$indexation"}, {$group:{_id:null, keys:{$addToSet:"$indexation.k"}}}])

对于较低版本，您必须将indexation更新为如下所示，并使用

For lower version you've to update indexation to look like below and and use

db.collection.distinct("indexation.k")

 { "_id" : ObjectId("58fb35531eb5df245d5d434f"), "name" : "d1.html", "indexation" : [{ "k" : "Citroen", "v" : 1 }, { "k" : "Marca", "v" : 1 }]}

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