CODEWITHSUNDEEP
javascriptnode.jsmongodbapimongoose
Quentin
Quentin

Reputation: 516

Why deleteOne & findById of mongoose work on deleted id

Currently developing an API with nodejs that communicates with a MongoDB database, I noticed a special behavior after deleting a document.

Indeed, my API has several endpoints that allow to retrieve all the animals in the database, to retrieve a specific one using the corresponding id or to delete a specific one, again using the id of the document to delete.

The results I don't understand happen once a document is deleted. Indeed, as you can see in the picture below, when I delete the document of the animal called "Johnny" the queries to find it via its id or to delete it via the same ID continue to work, even if the get returns nothing and the deletion indicates that no operation has been performed.

enter image description here

Personally I expected the same behavior as if I passed a wrong id for a deletion (visible below), but if the id has already been assigned in the database the queries work even after a deletion.

When I tried to deleted a wrong ID

Does MongoDB have a "cache" of deleted documents in order to perform a rollback in case of unwanted deletion?

You will find below the different endpoints that use find, deleteOne & findById


exports.getAllAnimal = (req, res, next) => {
    Animal.find().sort({'customer' : 1})
    .then(animals => res.status(200).send(animals))
    .catch(error => res.status(400).send({ error: error.message }));
};


exports.getOneAnimal = (req, res, next) => {
    Animal.findOne({ _id: req.params.id })
        .then(animal => res.status(200).send(animal))
        .catch(error => res.status(400).send({ error: error.message }));
};


exports.deleteAnimal = (req, res, next) => {
    Animal.deleteOne({ _id: req.params.id })
        .then(thing => res.status(200).send({ message : 'Animal successfully deleted'}))
        .catch(error => res.status(400).send({ error: error.message }));

};

Upvotes: 5

Views: 2427

Answers (1)

Algo7
Algo7

Reputation: 2166

MongoDB does not cache deleted id anywhere.

The thing is that when you said I passed a wrong id for a deletion ... you are passing an id with the same length but not in the required format. That's why Mongoose is throwing you an error.

However, if you follow the id structure of MongoDB to create an id that does not exist in the database and run an operation against it, MongoDB will still return you with success and an empty result.

Try using 5ea08034385a46666b05020f and run the .findById() query function against it. It's going to return you with a success an empty result.

The success only means that the operation is successful, but it doesn't necessarily mean that it actually finds something in the database.

I don't have access to your database, so the id is generated randomly but following the MongoDB ObjectId rules below:

The 12-byte ObjectId value consists of:

  1. a 4-byte timestamp value, representing the ObjectId’s creation, measured in
  2. seconds since the Unix epoch
  3. a 5-byte random value
  4. a 3-byte incrementing counter, initialized to a random value

Generate arbitrary MongoDB ObjectId: https://observablehq.com/@hugodf/mongodb-objectid-generator

Upvotes: 3

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