如何在mongodb中将字符串转换为数值 [英] how to convert string to numerical values in mongodb

问题描述

我正在尝试在MongoDB的聚合查询中将包含数字值的字符串转换为其值.

I am trying to convert a string that contains a numerical value to its value in an aggregate query in MongoDB.

文档示例

{
"_id": ObjectId("5522XXXXXXXXXXXX"),
   "Date": "2015-04-05",
   "PartnerID": "123456",
   "moop": "1234" 
}

我使用的汇总查询示例

{
    aggregate: 'my_collection',
    pipeline: [
         {$match: {
             Date : 
                  {$gt:'2015-04-01', 
                  $lt: '2015-04-05'
                  }}
             },
         {$group:
             {_id: "$PartnerID",
              total:{$sum:'$moop'}
             }}]}

结果是

{
   "result": [
     {
       "_id": "123456",
       "total": NumberInt(0) 
    }
}

如何将字符串转换为数字值?

How can you convert the string to its numerical value?

推荐答案

MongoDB聚合不允许更改给定字段的现有数据类型.在这种情况下，您应该创建一些编程代码以将string转换为int.检查以下代码

MongoDB aggregation not allowed to change existing data type of given fields. In this case you should create some programming code to convert string to int. Check below code

db.collectionName.find().forEach(function(data) {
    db.collectionName.update({
        "_id": data._id,
        "moop": data.moop
    }, {
        "$set": {
            "PartnerID": parseInt(data.PartnerID)
        }
    });
})

如果集合的大小大于上述脚本的大小，则会降低性能，对于perfomace mongo，请提供

If your collections size more then above script will slow down the performance, for perfomace mongo provide mongo bulk operations, using mongo bulk operations also updated data type

var bulk = db.collectionName.initializeOrderedBulkOp();
var counter = 0;
db.collectionName.find().forEach(function(data) {
    var updoc = {
        "$set": {}
    };
    var myKey = "PartnerID";
    updoc["$set"][myKey] = parseInt(data.PartnerID);
    // queue the update
    bulk.find({
        "_id": data._id
    }).update(updoc);
    counter++;
    // Drain and re-initialize every 1000 update statements
    if (counter % 1000 == 0) {
        bulk.execute();
        bulk = db.collectionName.initializeOrderedBulkOp();
    }
    })
    // Add the rest in the queue
if (counter % 1000 != 0) bulk.execute();

这基本上将发送到服务器的操作语句数量减少为每1000个排队的操作仅发送一次.

This basically reduces the amount of operations statements sent to the sever to only sending once every 1000 queued operations.

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