mongodb如何动态创建数据库/集合 [英] How does mongodb create database/collection on the fly

问题描述

如果我们运行类似于

db.store.save({a: 789});

它会自动创建 store 集合并添加一个记录它。

It automatically creates store collection and add a document to it.

我的javascript理解说，无法在 db 的未定义属性上调用方法宾语。它应该会导致某种错误/异常。

My javascript understanding says it is not possible to call a method on an undefined property of db object. It should have resulted in some kind of error/exception.

我很想知道幕后发生的事情，如果有任何有用的链接，请指出那些。谷歌搜索没有帮助我。

I am curious to understand the happenings behind the scene and if there is any helpful link please point me to those. Googling did not help me much.

推荐答案

我记得在NodeJS环境中你必须做这样的事情来实际创建一个记录： db.get（'collectionName'）。insert（{.. something ...}）; 或 db.get（'collectionName'） .save（{... something ...}）; 但你不能将集合名称用作db的属性。

As I recall in a NodeJS environment you must do something like this to actually create a record: db.get('collectionName').insert({..something...}); or db.get('collectionName').save({...something...}); but you don't get to use the collection name as a property of db.

您提到的行仅用于MongoDB shell，而不是Javascript。
我猜你误解了什么是MongoDB shell以及什么是MongoDB驱动程序。

The line you're mentioning is only used in MongoDB shell, which is not Javascript. I guess you're misunderstanding what's MongoDB shell and what's a MongoDB driver.

长篇故事MongoDB（驱动程序）无法访问未定义的属性。

So long story short MongoDB (driver) is not able to access an undefined property.

编辑

回复你的评论..

MongoDB JS驱动程序的GitHub页面几乎指出如何插入字段并始终使用我提到的语法： https://github.com/mongodb/node-mongodb-native

MongoDB JS driver's GitHub page pretty much points out how to insert a field and always uses the syntax I mentioned: https://github.com/mongodb/node-mongodb-native

至于你使用的是什么在shell中，很明显你不能只在命令shell中使用Javascript。所以我想我会指出一个你可以看到MongoDB开发的语言的地方： http：// www .mongodb.org / 几乎第一行说它是用C ++编写的。

As for what you're using in the shell it's pretty clear that you can't just use Javascript in a command shell. So I guess I'll point you to a place in which you can see in what language was MongoDB developed: http://www.mongodb.org/ pretty much the first line says it's written in C++.

希望这有助于澄清你的问题

Hope this helps clarify your question

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