如何在Mongodb中获取单个文档的大小?

问题描述

我遇到了mongo的奇怪行为，我想澄清一下...
我的要求很简单:我希望在集合中获得单个文档的大小.我找到了两种可能的解决方案:

I encountered a strange behavior of mongo and I would like to clarify it a bit...
My request is simple as that: I would like to get a size of single document in collection.I found two possible solutions:

• Object.bsonsize-一些应返回以字节为单位的大小的javascript方法
• db.collection.stats()-其中有一行"avgObjSize"，可在数据上生成一些汇总的"(平均)大小视图.它只代表单个文档的平均大小.

当我仅使用一个文档创建测试集合时，两个函数都返回不同的值.这怎么可能?
是否存在其他方法来获取mongo文档的大小?

• Object.bsonsize - some javascript method that should return a size in bytes
• db.collection.stats() - where there is a line 'avgObjSize' that produce some "aggregated"(average) size view on the data. It simply represents average size of single document.

When I create test collection with only one document, both functions returns different values. How is it possible?
Does it exist some other method to get a size of a mongo document?

在这里，我提供一些我要进行测试的代码:

Here, I provide some code I perform testing on:

1. 我创建了新的数据库"test"，并输入仅具有一个属性的简单文档:type:"auto"

1. I created new database 'test' and input simple document with only one attribute: type:"auto"

db.test.insert({type:"auto"})

stats()函数调用的

输出: db.test.stats():

output from stats() function call: db.test.stats():

{
  "ns" : "test.test",
  "count" : 1,
  "size" : 40,
  "avgObjSize" : 40,
  "storageSize" : 4096,
  "numExtents" : 1,
  "nindexes" : 1,
  "lastExtentSize" : 4096,
  "paddingFactor" : 1,
  "systemFlags" : 1,
  "userFlags" : 0,
  "totalIndexSize" : 8176,
  "indexSizes" : {
        "_id_" : 8176
},
"ok" : 1

}

输出: Object.bsonsize(db.test.find({test:"auto"}))

481

推荐答案

在上一个Object.bsonsize()调用中，Mongodb返回了游标的大小，而不是文档的大小.

In the previous call of Object.bsonsize(), Mongodb returned the size of the cursor, rather than the document.

正确的方法是使用此命令:

Correct way is to use this command:

Object.bsonsize(db.test.findOne())

使用findOne()，您可以定义特定文档的查询:

With findOne(), you can define your query for a specific document:

Object.bsonsize(db.test.findOne({type:"auto"}))

这将返回特定文档的正确大小(以字节为单位).

This will return the correct size (in bytes) of the particular document.

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