在使用MongoDB-Node.JS本机驱动器通过查询从MongoDB中获取字段时,如何重命名/别名字段? [英] How to rename/alias field(s) while fetching it from MongoDB through query using MongoDB-Node.JS native drive?
问题描述
考虑以下代码,我正在使用这些代码从本地MongoDB服务器中获取数据.
Consider the following code, which I am using to fetch the data from my local MongoDB server.
var Db = require('mongodb').Db,
MongoClient = require('mongodb').MongoClient,
Server = require('mongodb').Server,
ReplSetServers = require('mongodb').ReplSetServers,
ObjectID = require('mongodb').ObjectID,
Binary = require('mongodb').Binary,
GridStore = require('mongodb').GridStore,
Code = require('mongodb').Code,
BSON = require('mongodb').pure().BSON,
assert = require('assert');
var db = new Db('test', new Server('localhost', 27017));
db.open(function(err, db) {
db.createCollection('simple_limit_skip_find_one_query', function(err, collection) {
assert.equal(null, err);
collection.insert([{a:1, b:1}, {a:2, b:2}, {a:3, b:3}], {w:1}, function(err, result) {
assert.equal(null, err);
collection.findOne({a:1}, {fields:{b:1}}, function(err, doc) {
// I got the read document in the object 'doc'
});
});
});
});
现在,我想重命名一个字段名称,而仅检索(不在数据库中),例如,使用上面的代码,我在返回的对象doc
中有一个名为b
的字段,我希望它是baseID
而不是b
Now, I want to rename a field name while retrieving only (not in the DB), for example with the above code, I have a field named b
in the returned object doc
I want it to be baseID
instead of b
有什么办法吗?
注意:我无法对检索到的对象doc
进行操作来重命名JSON密钥重命名之类的字段.我希望查询它,而MongoDB也会一样.
Note: I cannot take action on the retrieved object doc
to rename field like JSON key renaming. I want it to be queried and MongoDB will the same.
推荐答案
使用升级 MongoDB服务器实例到> = 2.1).
Use aggregate framework of MonogDB (But you need to upgrade the MongoDB server instance to >= 2.1).
以下是上面示例的内容
var Db = require('mongodb').Db,
MongoClient = require('mongodb').MongoClient,
Server = require('mongodb').Server,
ReplSetServers = require('mongodb').ReplSetServers,
ObjectID = require('mongodb').ObjectID,
Binary = require('mongodb').Binary,
GridStore = require('mongodb').GridStore,
Code = require('mongodb').Code,
BSON = require('mongodb').pure().BSON,
assert = require('assert');
db.open(function (err, db) {
if (err) console.dir(err);
db.createCollection('simple_limit_skip_find_one_query', function (err, collection) {
if (err) console.dir(err);
collection.insert([{ a: 1, b: 1 }, { a: 2, b: 2 }, { a: 3, b: 3}], { w: 1 }, function (err, doc) {
if (err) console.dir(err);
collection.aggregate([
{ $project: {
a: 1,
_id:0,
baseID: "$b"
}
}
], function (err, doc) {
if (err) console.dir(err);
console.log(doc);
});
});
});
});
输出:
[ { a: 1, baseID: 1 },
{ a: 2, baseID: 2 },
{ a: 3, baseID: 3 }]
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