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mongodbmeteor
Billybobbonnet
Billybobbonnet

Reputation: 3226

In meteor/mongo collections, is the _id field unique in its collection or in the entire database?

I want to check that if I use _id fields that refer to documents from different collections, I will never have a duplicate _id, i.e. used in 2 different collections inside the same database.

Using meteor (so both in minimongo and mongodb), is the _id field unique in its collection or in the entire database?

Upvotes: 2

Views: 194

Answers (1)

Dmytro Shevchenko
Dmytro Shevchenko

Reputation: 34641

The _id values you have in your database are generated by Meteor using Random.id(). These are unique across all collections.

Please note that the uniqueness of _id values in MonogoDB is ensured on the collection level, meaning that there is always a unique index on the _id field for every collection. There is no MongoDB mechanism in place that would ensure _id uniqueness across collections.

In any case, it is quite a safe assumption that Meteor's random IDs will never collide.

Upvotes: 3

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