JavaScript JSON Cookbook by unknow

Author:unknow
Language: eng
Format: mobi
Publisher: Packt Publishing

Note that the objects have the same fields, but they also have an additional _id field, which is the unique id of the object in the database. In the next section, you will learn how to query on that.

There's more

What happens if you insert the same object multiple times into the database? Try it! You'll see that you get multiple copies of the object in the database; the fields aren't used to specify uniqueness (the exception is the _id field, which is unique across the database). Note that you can't specify an _id field yourself, unless you're assured that it's unique. To update an existing element, use the update method, which I described in the recipe Updating a document in MongoDB with Node.js in this chapter.

By default, MongoDB insertions operate quickly and might fail (say, if there's a transitory network problem, or if the server is temporarily overloaded). At the cost of performance, you can pass { safe: true } as the second argument to insert or to force the operation to wait for a successful operation or return an error if the operation fails.

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