Mongo将嵌入式文档转换为数组

问题描述

有没有一种方法可以将嵌套的文档结构转换为数组?下面是一个示例:

Is there a way to convert a nested document structure into an array? Below is an example:

输入

"experience" : {
        "0" : {
            "duration" : "3 months",
            "end" : "August 2012",
            "organization" : {
                "0" : {
                    "name" : "Bank of China",
                    "profile_url" : "http://www.linkedin.com/company/13801"
                }
            },
            "start" : "June 2012",
            "title" : "Intern Analyst"
        }
    },

预期输出:

"experience" : [
           {
            "duration" : "3 months",
            "end" : "August 2012",
            "organization" : {
                "0" : {
                    "name" : "Bank of China",
                    "profile_url" : "http://www.linkedin.com/company/13801"
                }
            },
            "start" : "June 2012",
            "title" : "Intern Analyst"
        }
    ],

目前，我正在使用脚本来遍历每个元素，并将它们转换为数组&最终更新文档.但这要花费很多时间，有没有更好的方法呢?

Currently I am using a script to iterate over each element, convert them to an array & finally update the document. But it is taking a lot of time, is there a better way of doing this?

推荐答案

您仍然需要遍历内容，但是应该使用批量操作来写回:

You still need to iterate over the content, but instead you should be writing back using bulk operations:

对于MongoDB 2.6和更高版本:

Either for MongoDB 2.6 and greater:

var bulk = db.collection.initializeUnorderedBulkOp(),
    count = 0;

db.collection.find({
   "$where": "return !Array.isArray(this.experience)"
}).forEach(function(doc) {
    bulk.find({ "_id": doc._id }).updateOne({
        "$set": { "experience": [doc.experience["0"]] }
    });
    count++;

    // Write once in 1000 entries
    if ( count % 1000 == 0 ) {
        bulk.execute();
        bulk = db.collection.initializeUnorderedBulkOp();
    }
})

// Write the remaining
if ( count % 1000 != 0 )
    bulk.execute();

或者在现代版本的MongoDB 3.2和更高版本中， bulkWrite() 方法:

Or in modern releases of MongoDB 3.2 and greater, the bulkWrite() method is preferred:

var ops = [];

db.collection.find({
   "$where": "return !Array.isArray(this.experience)"
}).forEach(function(doc) {
   ops.push({
       "updateOne": {
           "filter": { "_id": doc._id },
           "update": { "$set": { "experience": [doc.experience["0"]] } }
       }
   });

   if ( ops.length == 1000 ) {
       db.collection.bulkWrite(ops,{ "ordered": false })
       ops = [];
   }
})

if ( ops.length > 0 )
    db.collection.bulkWrite(ops,{ "ordered": false });

因此，当通过游标写回数据库时，必须进行设置为无序"的批量写操作.每1000个请求中只有一个写入/响应，这减少了很多开销，并且无序"意味着写入可以并行发生，而不是串行发生.这一切都使其变得更快.

So when writing back to the database over a cursor, then bulk write operations with "unordered" set is the way to go. It's only one write/response per batch of 1000 requests, which reduces a lot of overhead, and "unordered" means that writes can happen in parallel rather than in a serial order. It all makes it faster.

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