什么时候将文档添加到MongoDB集合中

本文介绍了什么时候将文档添加到MongoDB集合中的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我有一个现有的mongodb集合，该集合没有有关文档创建时间的任何信息.

I have an existing mongodb collection, which doesn't have any information about when the document was created.

是否有可能以某种方式获取此信息?我浏览了所有文档，但在任何地方都看不到.

Is it possible to get this information some how? I've had a look through the docs but can't see it anywhere.

推荐答案

如果您为_id属性使用默认的ObjectId值，则创建时间将在其中进行编码.

If you are using the default ObjectId value for your _id attribute, the creation time is encoded inside it.

如 ObjectID文档所述:

ObjectId是一种12字节的BSON类型，使用以下方式构造:

ObjectId is a 12-byte BSON type, constructed using:

• 一个4字节的值，表示自Unix时代以来的秒，
• 3字节机器标识符
• 从随机值开始的2字节进程ID和3字节计数器.

• a 4-byte value representing the seconds since the Unix epoch,
• a 3-byte machine identifier
• a 2-byte process id, and a 3-byte counter, starting with a random value.

您可以在ObjectId对象上调用getTimestamp()函数，以获取包含对象创建时间的ISODate对象:

You can call the getTimestamp() function on an ObjectId object to get an ISODate object containing the creation time of the object:

在mongo shell中:

ObjectId().getTimestamp() ISODate("2014-05-14T14:29:12Z")