How to create a new document 'if not exists' and return the new document with MongoDB NodeJS native driver

Question

I want to create a new document if it doesn't exist and return the new document once created, however if the document already exists I would like an exception to be thrown.

I think the way I am doing this seems hackish, is there a better means of doing this?

var query = { name: 'guaranteed to be unique' }
var new_doc = { ... }
var col = // the Mongo collection we're using

col.updateOne(
    query,
    new_doc,
    {upsert: true}
)
.then(update => col.findOne({_id, update.result.upserted.pop()._id}))
.then(doc => console.log(doc))
.catch( exception => console.log('that already exists') )

Depends if you want to update it if it does exist? If so you could just use `{upsert:true}` on `update`. Otherwise you've done it correctly. — Matt The Ninja, Jun 20 '16 at 17:08
@robertklep, could you explain how a unique index would solve this? — Aage Torleif, Jun 20 '16 at 19:35
@MatUtter insert `new_doc`, if name exists already you'll get an uniqueness violation error, if name doesn't exist the document has been inserted and you can retrieve the document from the result. — robertklep, Jun 20 '16 at 20:09

score 1 · Answer 1 · edited May 23 '17 at 12:08

1

After a lot a searching I found some answers in this post, but here's a clean example with findOneAndUpdate and the returnOriginal property set false

col.findOneAndUpdate(
    query,
    new_doc,
    { upsert: true, returnOriginal:false }
)
.then(update => update.value)
.then(doc => console.log(doc))

edited May 23 '17 at 12:08

Community

1
1

answered Jun 20 '16 at 19:39

Aage Torleif

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Be aware that any properties in `new_doc` will overwrite the properties in the database if the document already exists. – robertklep Jun 20 '16 at 20:11

How to create a new document 'if not exists' and return the new document with MongoDB NodeJS native driver

1 Answers1