Question

收集文件1

{
    "_id" : ObjectId("5c2ee03224acf45a663d8f09"),
    "_class" : "document.domain.DDD",
    "generated" : false,
    "linkIds" : [],
    "types" : [],
    "metadata" : {       
        "templateId" : "ABDC",
        "userId" : "Master"
    }
    "versions" : [ 
        {
            "revision" : "fb4fb8ec-edfe-4a3e-a1a9-c8c4b2bce678",
            "fileId" : "5c2ee03224acf45a663d8f08"
        }
    ]
}

collection B document 1

{
    "_id" : ObjectId("5c2ee03224acf45a663d8f08"),
    "_class" : "document.domain.RDF",
    "extension" : ".pdf",
    "rootPath" : "D"
    "size" : 152754
 }

集合A，文档1中的字段ID在集合B doc 1的objectid中显示为字符串。

如何在集合B中查找显示为objecid的字符串？

Answer 1

您必须在那里使用mongodb聚合你有更多的看法 https://docs.mongodb.com/manual/core/aggregation-pipeline/ 并且您必须使用$ lookup运算符更多了解 https://docs.mongodb.com/manual/reference/operator/aggregation/lookup/

您可以完成此任务

  collectionA.aggregate.([
    {
    $match:{},// To match  and get all doc
    },
    {
       $lookup:
         {
           from: collection B//<collection to join>,
           localField: versions.fileId//<field from the input documents>,
           foreignField: _id//<field from the documents of the "from" collection>,
           as: versions.file//<output array field>
         }
    }])

mongodb仅显示objectId的str

1 个答案: