What is the actual difference between findOneAndUpdate and findOneAndReplace

[Rafał Ruciński]

Hello,

I've recently installed the newest version of node-mongodb-native, 2.0.45.

I've been looking for the findAndModify method that I've been using before and found out it got deprecated in the meantime, and is now replaced by findOneAndUpdate and findOneAndReplace.

As I was wondering how did findOneAndReplace come about, I looked into the source code and found out that both of the new methods are almost identical.

To be extra sure, I've performed a test:

var _id;

Post.insertOne({ a: 1 })
  .then((result) => {
    _id = result.insertedId;


    return Post.find({ _id }).limit(1).next();
  })
  .then((result) => {
    console.log(result);


    return Post.findOneAndUpdate({ _id }, { $set: { b: 1 } }, { returnOriginal: false });
  })
  .then((result) => {
    console.log(result);


    return Post.findOneAndReplace({ _id }, { $set: { c: 1 } }, { returnOriginal: false });
  })
  .then((result) => {
    console.log(result);
  });

and the result was:

{ _id: 561d483c5e0f7e684c1f88d8, a: 1 }

{ value: { _id: 561d483c5e0f7e684c1f88d8, a: 1, b: 1 },

  lastErrorObject: { updatedExisting: true, n: 1 },

  ok: 1 }

{ value: { _id: 561d483c5e0f7e684c1f88d8, a: 1, b: 1, c: 1 },

  lastErrorObject: { updatedExisting: true, n: 1 },

  ok: 1 }

The docs for findOneAndReplace suggest that the last object should look more like this:

{ _id: 561d483c5e0f7e684c1f88d8, c: 1 }

So what's the deal with this method? Why does it do the same as findOneAndUpdate?

[Rafał Ruciński]

Can someone please answer? :(

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[Christian Kvalheim]

In practice nothing it's just a convenience method.

The values returned are due to this API being implemented before they revised the current crud specification. Always look at the actual driver API not the crud spec.

http://mongodb.github.io/node-mongodb-native/2.0/api/Collection.html#~findAndModifyWriteOpResult

Changing this will not be possible until at least 3.0.0

results are always

Name	Type	Description
value	object	Document returned from findAndModify command.
lastErrorObject	object	The raw lastErrorObject returned from the command.
ok	Number	Is 1 if the command executed correctly.

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