从不同的数据库更新集合 [英] Updating a collection from a different database
问题描述
我正在使用 Mongo 4.1 并希望更新名为location_copy"的集合，方法是向其添加一个名为time"的类型对象的新字段，其中包含两个子字段:utcTime"，它将是由该文档时间"的值填充字段和tz"，它们将由subject.contactInf[0].addresses[0].timeZoneID"的值填充；from 集合subjects"中的文档在数据库主题"中(与第一个集合中的数据库不同的数据库)带有_id"；对应于subjectID"的字段值location_copy 中的字段.
I'm using Mongo 4.1 and would like to update a collection named "location_copy", by adding a new field to it of type object named "time", with two subfields: "utcTime", which will be populated by the value of that documents "time" field, and "tz", which will be populated by value of "subject.contactInf[0].addresses[0].timeZoneID" from of the document in the collection "subjects" in the database "Subjects" (a different database from the one of the first collection) with "_id" field value corresponding to "subjectID" field in locations_copy.
我尝试使用以下代码完成此操作:
I have tried to accomplish this with the following code:
const get_time_zone_id = function(doc) {return doc.contactInfo[0].addresses[0].timeZoneID}
const get_location_doc = function(subjectID) { return db.getSiblingDB('Subjects').subjects.find({"_id": subjectID, "contactInfo": {"$exists": true}, "$where" : function() {
return (this.contactInfo.length > 0 && this.contactInfo[0].addresses && this.contactInfo[0].addresses.length > 0 && this.contactInfo[0].addresses[0].timeZoneID)
}}, {"contactInfo" : {"$slice": 1}, "contactInfo.addresses": {"$slice": 1},"contactInfo.addresses.timeZoneID" : 1}).map(get_time_zone_id)}
db.locations_copy.aggregate( [
{ $match: {"subjectID": {"$exists": true}}},
{ $addFields: {
time: { utc: "$timeUTC",
tz: { "$arrayElemAt": [get_location_doc(ObjectId("$subjectID")), 0 ] }}
}
}
] ).forEach(function(x){db.locations_copy.save(x)})
除了一件事之外，一切正常:当我尝试将 ObjectId($subjectID") 作为参数传递给get_location_doc"时，它解析$subjectID"；作为文字字符串，而不是在每个文档中传递基础字段的值.我也试过简单地传递 subjectID(不带引号)，在这种情况下它只是未定义，或者$$subjectID"这使我再次使用文字字符串.我知道这是由于客户端/服务器端在运行时解析造成的.我曾尝试使用$function"运算符，但显然它仅适用于 4.4 版(我使用的是 4.1).我应该注意，如果我将$subjectID"替换为使用硬编码的字符串 ID(例如5ff4c037bc0a716381231277")，一切都如您所愿.任何人都可以帮助我完成我的意图吗?由于此脚本仅打算执行一次，因此性能问题不大.
everything works except for one thing: when I try to pass ObjectId("$subjectID") as a parameter to "get_location_doc", it parses "$subjectID" as a literal string rather than passing the value of the underlying field in each document. I have also tried passing simply subjectID (without quotes) in which case it was simply undefined, or "$$subjectID" which led me to a literal string again. I understand this is due to client/server side parsing in run time. I have tried to utilize the "$function" operator, but apparently it's only available from version 4.4 (I'm using 4.1). I should note, that if I replace "$subjectID" with a hard-coded string ID (for example "5ff4c037bc0a716381231277") everything works as you'd expect. Can anyone please help me accomplish what I intend? since this script is only meant to be executed once, performance is not much of an issue.
谢谢！
推荐答案
db.getSiblingDB().collection.find() 是一个客户端操作.它不是您可以用来将集合作为查询的一部分加入的东西.为此，请参阅 https://docs.mongodb.com/manual/reference/operator/aggregation/lookup/.
db.getSiblingDB().collection.find() is a client-side operation. It is not something you can use to join collections as part of a query. For that, see https://docs.mongodb.com/manual/reference/operator/aggregation/lookup/.
您要做的第二件事是从文档中检索嵌套字段.你可以用 $set 和点符号来做到这一点.具体参见 中的示例https://docs.mongodb.com/manual/reference/operator/aggregation/set/#adding-fields-to-an-embedded-document.
The second thing you are doing is retrieving nested fields out of a document. You can do this with $set and dot notation. See specifically the example at https://docs.mongodb.com/manual/reference/operator/aggregation/set/#adding-fields-to-an-embedded-document.
您将需要构建一个单一的聚合管道，该管道仅使用 https://docs.mongodb.com/manual/reference/operator/aggregation/ 和 https://docs.mongodb.com/manual/reference/operator/aggregation-pipeline/.
You will need to construct a single aggregation pipeline that does everything your current mix of aggregation and javascript does using only the operations documented in https://docs.mongodb.com/manual/reference/operator/aggregation/ and the stages documented in https://docs.mongodb.com/manual/reference/operator/aggregation-pipeline/.
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