mongodb using mongoose: E11000 duplicate key error on .save with nested collection

Question

I'm trying to create a Project entry, it has a languages array which I want to describe as

languages can (will) be initially empty [], and each object within it must have a field called key which must be unique.

e.g:

{
  languages: [],
  ....
}

or:

{
  languages: [ { key: 'en-US } ],
  ...
}

The mongoose Schema looks like:

{
  languages: [{
    key: {
      type: String,
      unique: true,
    },
  }],
  ...
}

The first creation works:

const project = new Project({
  name,
  owner: user,
});

await project.save();

However thereafter I get this error about already having a language with key: null, even though the languages array is empty...

{ MongoError: E11000 duplicate key error collection: yebu.projects index: tags.name_1 dup key: { : null }
    at Function.MongoError.create (<redacted>/node_modules/mongodb-core/lib/error.js:31:11)
...

I tried sparse: true in the key field but to no avail.

nanobar · Accepted Answer · 2017-11-04 17:23:34Z

1

As this answer mentions: Mongodb unique sparse index

The answer was to combine unique: true with sparse: true. I wasn't noticing that it was working as my next collection in the schema was failing until I added it there too.

answered Nov 4, 2017 at 17:23

nanobar

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Comments

Ankit Kumar Rajpoot · Accepted Answer · 2020-04-10 14:21:36Z

0

Try this - combine unique: true, sparse: true with default: null

{
  languages: [{
    key: {
      type: String,
      default: null
      unique: true,
    },
  }],
  ...
}

answered Apr 10, 2020 at 14:21

Ankit Kumar Rajpoot

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