CamelCamelCamel
Reputation: 5200
MongoDB :: are Mongo IDs unique across collections?
Can Mongo IDs have the same value in different collections in the same database?
Upvotes: 73
Views: 25709
Answers (1)
svjson
Reputation: 2115
The uniqueness constraint for _id is per collection, so yes - one and the same ID can occur once per Collection.
It's however very unlikely, if not impossible, for the same ID to be generated twice. So in order for this to happen you would have to manually insert duplicate IDs.
Upvotes: 79
Related Questions
- Is MongoDB _id unique by default?
- Is Mongodb ObjectID unique between documents?
- Are MongoDB document IDs unique to the entire database or just that collection?
- Make _id index unique in a mongodb collection
- Possibility of duplicate Mongo ObjectId's being generated in two different collections?
- In meteor/mongo collections, is the _id field unique in its collection or in the entire database?
- In MongoDB, how likely is it two documents in different collections in the same database will have the same Id?
- Unique ids in MongoDB
- Are embedded document ids unique in the collection?
- In MongoDB, do document _id's need to be unique across a collection or the entire DB?