How do I remove the duplicate Key check before insert in mongoDB?-CodePudding

I use mongoDB to manage my DB for a yearly contest. Every year many users just renew their registration. MongoDB rejects duplicate emails, therefore they cannot register if they participated any of the edition of early years.

My question, is there any way to remove that limitation? Or maybe change the dup-key-check to be i.e. the "_id" (or whatever) instead of the "email"?

CodePudding user response：

Apart from the mandatory _id field, MongoDB will only enforce uniqueness based on additional unique indexes that have been created. In your situation it sounds like there may be a unique index defined on { email: 1 }.

If that is not the logic that you wish to enforce, then you should drop that index and replace it with a different one. How exactly you define that really depends on your desired application logic. If you had a registrationYear field, for example, perhaps a compound unique index on both of those fields ({ email: 1, registrationYear: 1 }) would be appropriate.

But this probably isn't the only way to solve the problem. An alternative approach may be to combine a unique index with a partial index. With this approach, you could define as index as follows assuming that there is some active field in the document that becomes false after the specified amount of time:

db.foo.createIndex({ email: 1}, { unique: true, partialFilterExpression: { active: true } })

Such an index would only include documents that were currently considered active therefore only enforcing uniqueness on them. Once it was time to renew and an old document was no longer active the database would accept a new one.

Another alternative approach would be to just update the existing documents rather than creating new ones. Again this depends on what exactly you are trying to achieve, but you could use a similar approach of marking a document as no longer active and having the registration process perform an upsert (either an insert or an update).

Finally, if you don't need historical information at all then you could additionally do some sort of archival or deletion (perhaps via a TTL index) to expire the old documents.